1, Nover.bmp
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous metabolites from the body."
"T"
"This is the definition of nitrogen balance: the simple difference between intake and output. Balance = intake - excretion."
"Nitrogen balance is the ratio of intake of nitrogenous compounds / output of nitrogenous metabolites from the body."
"F"
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous metabolites from the body. Balance = intake - excretion."
2, Nover.bmp
"In positive nitrogen balance the excretion of nitrogenous metabolites is greater than the dietary intake of nitrogenous compounds."
"F"
"Positive nitrogen balance means intake > excretion."
"In positive nitrogen balance the excretion of nitrogenous metabolites is less than the dietary intake of nitrogenous compounds."
"T"
"Positive nitrogen balance means intake > excretion."
3, Nover.bmp
"In negative nitrogen balance the excretion of nitrogenous metabolites is greater than the dietary intake of nitrogenous compounds."
"T"
"Negative nitrogen balance means excretion > intake."
"In negative nitrogen balance the excretion of nitrogenous metabolites is less than the dietary intake of nitrogenous compounds."
"F"
"Negative nitrogen balance means excretion > intake."
4, Nover.bmp
"In nitrogen equilibrium the excretion of nitrogenous metabolites is greater than the dietary intake of nitrogenous compounds."
"F"
"Nitrogen equilibrium means intake = output."
"In nitrogen equilibrium the excretion of nitrogenous metabolites is less than the dietary intake of nitrogenous compounds."
"F"
"Nitrogen equilibrium means intake = output."
5, Nover.bmp
"In positive nitrogen balance the dietary intake of nitrogenous compounds is greater than the output of nitrogenous metabolites."
"T"
"Positive nitrogen balance means intake > excretion."
"In positive nitrogen balance the dietary intake of nitrogenous compounds is less than the output of nitrogenous metabolites."
"F"
"Positive nitrogen balance means intake > excretion."
6, Nover.bmp
"In negative nitrogen balance the dietary intake of nitrogenous compounds is greater than the output of nitrogenous metabolites."
"F"
"Negative nitrogen balance means intake < excretion."
"In negative nitrogen balance the dietary intake of nitrogenous compounds is less than the output of nitrogenous metabolites."
"T"
"Negative nitrogen balance means intake < excretion."
7, Nover.bmp
"If the intake of protein is greater than requirements, there will always be positive nitrogen balance."
"F"
"Nitrogen balance (equilibrium) can be maintained at any intake of protein above the minimum that is necessary. If the intake is greater than requirements, then excretion will be high, and nitrogen equilibrium (zero balance) will be maintained."
"If the intake of protein is greater than requirements, there will always be negative nitrogen balance."
"F"
"Nitrogen balance (equilibrium) can be maintained at any intake of protein above the minimum that is necessary. If the intake is greater than requirements, then excretion will be high, and nitrogen equilibrium (zero balance) will be maintained. Negative balance only occurs when the output of nitrogenous metabolites is greater than the intake."
8, Nover.bmp
"If the intake of protein is less than requirements, there will always be negative nitrogen balance."
"T" 
"If intake is inadequate to meet requirements then amino acids will not be available for the synthesis of proteins to replace those that have been broken down, so there will be a nett loss of body protein - this is negative nitrogen balance, since output of nitrogenous compounds is greater than intake."
"If the intake of protein is less than requirements, there will always be positive nitrogen balance."
"F"
"If intake is inadequate to meet requirements then amino acids will not be available for the synthesis of proteins to replace those that have been broken down, so there will be a nett loss of body protein - this is negative nitrogen balance, since output of nitrogenous compounds is greater than intake."
9, Nover.bmp
"Positive nitrogen balance means that there is a nett loss of protein from the body."
"F"
"Positive balance means intake > excretion, therefore there must be a nett gain in body nitrogen, and hence an increase in total body protein."
"Negative nitrogen balance means that there is a nett loss of protein from the body."
"T"
"Negative balance means intake < excretion, therefore there must be a nett loss of body nitrogen, and hence an decrease in total body protein."
10, Nover.bmp
"Positive nitrogen balance means that there is a gain of protein in the body."
"T"
"Positive balance means intake > excretion, therefore there must be a nett gain in body nitrogen, and hence an increase in total body protein."
"Negative nitrogen balance means that there is a gain of protein in the body."
"F"
"Negative balance means intake < excretion, therefore there must be a nett loss of body nitrogen, and hence a decrease in total body protein."
11, Nover.bmp
"Positive nitrogen balance occurs during post-operative convalescence."
"T"
"Convalescence is the recovery period; during this time there is replacement of protein that was lost as a result of the trauma of surgery. Since nitrogen is being retained in the body, in the form of this replacement protein, there will indeed be positive nitrogen balance; excretion will be less than intake."
"Negative nitrogen balance occurs during post-operative convalescence."
"F"
"Convalescence is the recovery period; during this time there is replacement of protein that was lost as a result of the trauma of surgery. Since nitrogen is being retained in the body, in the form of this replacement protein, there will be positive nitrogen balance; excretion will be less than intake."
12, Nover.bmp
"Positive nitrogen balance occurs during growth."
"T"
"During growth there is an increase in the total body content of protein. This means that intake must be > output, so there is indeed positive nitrogen balance during growth."
"Negative nitrogen balance occurs during growth."
"F"
"During growth there is an increase in the total body content of protein. This means that intake must be > output, so there is positive nitrogen balance during growth."
13, Nover.bmp
"Nitrogen balance is the ratio of essential to non-essential amino acids in the diet."
"F"
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous compounds from the body."
"Nitrogen balance is the difference between essential and non-essential amino acids in the diet."
"F"
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous compounds from the body."
14, Nover.bmp
"Positive nitrogen balance occurs if the diet is deficient in an essential amino acid."
"F"
"Lack of an essential amino acid will mean that it is impossible to maintain nitrogen balance - there will be negative nitrogen balance since the lacking amino acid will not be available for synthesis of protein to replace the protein that has been broken down."
"Negative nitrogen balance occurs if the diet is deficient in an essential amino acid."
"T"
"Lack of an essential amino acid will mean that it is impossible to maintain nitrogen balance - there will be negative nitrogen balance since the lacking amino acid will not be available for synthesis of protein to replace the protein that has been broken down."
15, Nover.bmp
"Positive nitrogen balance occurs if the diet provides more than the requirement of one or more essential amino acids."
"F"
"Nitrogen balance (equilibrium) can be maintained at any intake of protein (or individual amino acids) above the requirement. If the intake is greater than requirements, then excretion will be high, and nitrogen equilibrium (zero balance) will be maintained."
"Negative nitrogen balance occurs if the diet provides more than the requirement of one or more essential amino acids."
"F"
"Nitrogen balance (equilibrium) can be maintained at any intake of protein (or individual amino acids) above the requirement. If the intake is greater than requirements, then excretion will be high, and nitrogen equilibrium (zero balance) will be maintained."
16, Nover.bmp
"Nitrogen balance is the difference between protein intake and energy expenditure."
"F"
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous compounds from the body."
"Nitrogen balance proportion of energy that is derived from dietary protein."
"F"
"Nitrogen balance is the difference between the intake of nitrogenous compounds in the diet and the output of nitrogenous compounds from the body."
17, Nover.bmp
"Essential amino acids must be provided in the diet if nitrogen balance is to be maintained."
"T"
"This is the definition of essential amino acids - those that cannot be synthesized in the body, and without which nitrogen balance cannot be maintained."
"Nitrogen balance can be maintained even if the diet is lacking one or more essential amino acids."
"F"
"The definition of essential amino acids is those that cannot be synthesized in the body, and without which nitrogen balance cannot be maintained."
18, Nover.bmp
"All of the non-essential amino acids must be provided in the diet if nitrogen balance is to be maintained."
"F"
"The non-essential amino acids are those that can be synthesized in the body, and therefore it is possible to maintain nitrogen balance without supplying all of the non-essential amino acids - providing that total protein intake is adequate to permit synthesis of the non-essential amino acids."
"Nitrogen balance can be maintained even if the diet is lacking one or more non-essential amino acids."
"T"
"The non-essential amino acids are those that can be synthesized in the body, and therefore it is possible to maintain nitrogen balance without supplying all of the non-essential amino acids - providing that total protein intake is adequate to permit synthesis of the non-essential amino acids."
19, transam.bmp
"Only essential amino acids undergo transamination."
"F"
"All the amino acids (except lysine) undergo transamination."
"Only non-essential amino acids undergo transamination."
"F"
"All the amino acids (except lysine) undergo transamination."
20, transam.bmp
"Even if the keto-acid (oxo-acid) is provided, most essential amino acids cannot be synthesized by transamination."
"F"
"If the keto-acid is provided, all essential amino acids except lysine can be synthesized by transamination. However, there is no metabolic source of the keto-acids of the essential amino acids other than the amino acids themselves."
"If the keto-acid (oxo-acid) is provided, most essential amino acids can be synthesized by transamination."
"T"
"If the keto-acid is provided, all essential amino acids except lysine can be synthesized by transamination. However, there is no metabolic source of the keto-acids of the essential amino acids other than the amino acids themselves."
21, tyr.bmp
"Tyrosine is not an essential amino acid, but is synthesized from an essential amino acid precursor."
"T"
"Although tyrosine can readily be synthesized in the body, its immediate precursor is phenylalanine, which is an essential amino acid. Indeed, the main pathway of phenylalanine catabolism is by way of hydroxylation to tyrosine."
"Tyrosine is an essential amino acid and is the precursor for phenylalanine synthesis."
"F"
"It is phenylalanine that is the essential amino acid precursor for tyrosine synthesis."
22, phe.bmp
"Tryptophan is not an essential amino acid, but is synthesized from phenylalanine, which is an essential amino acid."
"F"
"Tryptophan is an essential amino acid - it is tyrosine that is synthesized from phenylalanine (which is shown in the diagram)."
"Threonine is not an essential amino acid, but is synthesized from phenylalanine, which is an essential amino acid."
"F"
"Threonine is an essential amino acid - it is tyrosine that is synthesized from phenylalanine (which is shown in the diagram)."
23, met.bmp
"Methionine is not an essential amino acid, but is synthesized from an essential amino acid precursor."
"F"
"Methionine is an essential amino acid. Although cysteine can be formed from methionine, the pathway is not reversible, and methionine cannot be synthesized from cysteine."
"Methionine is an essential amino acid, and is the precursor for synthesis of cysteine."
"T"
"Methionine is indeed an essential amino acid, and is also the precursor for cysteine synthesis."
24, ala.bmp
"Alanine is a conditionally essential amino acid."
"F"
"Alanine is a non-essential amino acid - it can readily be synthesized from pyruvate, which is a common metabolic intermediate."
"Alanine is a non-essential amino acid."
"T"
"Alanine can readily be synthesized from pyruvate, which is a common metabolic intermediate."
25, glu.bmp
"Glutamate is a conditionally essential amino acid."
"F"
"Glutamate is a non-essential amino acid - it can readily be synthesized from ketoglutarate, which is a common metabolic intermediate."
"Glutamate is a non-essential amino acid."
"T"
"Glutamate can readily be synthesized from ketoglutarate, which is a common metabolic intermediate."
26, asp.bmp
"Aspartate is a conditionally essential amino acid."
"F"
"Aspartate is a non-essential amino acid - it can readily be synthesized from oxaloacetate, which is a common metabolic intermediate."
"Aspartate is a non-essential amino acid."
"T"
"Aspartate can readily be synthesized from oxaloacetate, which is a common metabolic intermediate."
27, pro.bmp
"Proline is an essential amino acid."
"F"
"Proline can be synthesized in the body."
"Proline is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for proline may be greater than the capacity to synthesize it in the body."
28, gly.bmp
"Glycine is an essential amino acid."
"F"
"Glycine can be synthesized in the body."
"Glycine is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for glycine may be greater than the capacity to synthesize it in the body."
29, ser.bmp
"Serine is an essential amino acid."
"F"
"Serine can be synthesized in the body."
"Serine is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for serine may be greater than the capacity to synthesize it in the body."
30, asn.bmp
"Asparagine is an essential amino acid."
"F"
"Asparagine can be synthesized in the body."
"Asparagine is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for asparagine may be greater than the capacity to synthesize it in the body."
31, gln.bmp
"Glutamine is an essential amino acid."
"F"
"Glutamine can be synthesized in the body."
"Glutamine is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for glutamine may be greater than the capacity to synthesize it in the body."
32, arg.bmp
"Arginine is an essential amino acid."
"F"
"Arginine can be synthesized in the body."
"Arginine is a conditionally essential amino acid."
"T"
"Under some circumstances the requirement for arginine may be greater than the capacity to synthesize it in the body."
33, leu.bmp
"Leucine is an essential amino acid."
"T"
"Leucine cannot be synthesized in the body, so it is an essential amino acid."
"Leucine is a conditionally essential amino acid."
"F"
"Leucine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
34, ile.bmp
"Isoleucine is an essential amino acid."
"T"
"Isoleucine cannot be synthesized in the body, so it is an essential amino acid."
"Isoleucine is a conditionally essential amino acid."
"F"
"Isoleucine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
35, val.bmp
"Valine is an essential amino acid."
"T"
"Valine cannot be synthesized in the body, so it is an essential amino acid."
"Valine is a conditionally essential amino acid."
"F"
"Valine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
36, met.bmp
"Methionine is an essential amino acid."
"T"
"Methionine cannot be synthesized in the body, so it is an essential amino acid."
"Methionine is a conditionally essential amino acid."
"F"
"Methionine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
37, phe.bmp
"Phenylalanine is an essential amino acid."
"T"
"Phenylalanine cannot be synthesized in the body, so it is an essential amino acid."
"Phenylalanine is a conditionally essential amino acid."
"F"
"Phenylalanine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
38, trp.bmp
"Tryptophan is an essential amino acid."
"T"
"Tryptophan cannot be synthesized in the body, so it is an essential amino acid."
"Tryptophan is a conditionally essential amino acid."
"F"
"Tryptophan cannot be synthesized in the body, so it is an essential amino acid under all conditions."
39, thr.bmp
"Threonine is an essential amino acid."
"T"
"Threonine cannot be synthesized in the body, so it is an essential amino acid."
"Threonine is a conditionally essential amino acid."
"F"
"Threonine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
40, his.bmp
"Histidine is an essential amino acid."
"T"
"Histidine cannot be synthesized in the body, so it is an essential amino acid."
"Histidine is a conditionally essential amino acid."
"F"
"Histidine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
41, lys.bmp
"Lysine is an essential amino acid."
"T"
"Lysine cannot be synthesized in the body, so it is an essential amino acid."
"Lysine is a conditionally essential amino acid."
"F"
"Lysine cannot be synthesized in the body, so it is an essential amino acid under all conditions."
42, blank.bmp
"Some essential amino acids can be synthesized from metabolic intermediates."
"F"
"None of the essential amino acids can be synthesized in the body, since their carbon skeletons cannot be synthesized except from the amino acid itself."
"Essential amino acids are only required at times of growth or recovery from protein loss."
"F"
"There is always a need for essential amino acids, to permit replacement synthesis of those proteins that have been broken down as part of the normal turnover of tissue proteins."
43, blank.bmp
"Cystine is formed in proteins after translation."
"T"
"Cystine is the disulphide oxidation product of cysteine. It is especially important in the cross-linking of different parts of the peptide chain, or separate peptide chains. The oxidation to cystine occurs after cysteine has been incorporated into the protein, although commonly while the growing peptide chain is still bound to the ribosome, before synthesis of the complete peptide chain is complete."
"Cysteine is formed in proteins after translation."
"F"
"Cysteine is incorporated into proteins during synthesis. Cystine is the disulphide oxidation product of cysteine. It is especially important in the cross-linking of different parts of the peptide chain, or separate peptide chains. The oxidation to cystine occurs after cysteine has been incorporated into the protein, although commonly while the growing peptide chain is still bound to the ribosome, before synthesis of the complete peptide chain is complete."
44, blank.bmp
"gamma-Carboxyglutamate is incorporated into proteins during synthesis on the ribosome."
"F"
"gamma-Carboxyglutamate is formed in proteins after translation by carboxylation of glutamate residues. The vitamin K dependent reaction is important in a number of calcium-binding proteins, including prothrombin and other blood-clotting proteins, where binding of calcium to a region of the protein containing several gamma-carboxyglutamate residues close together is essential for biological activity."
"gamma-Carboxyglutamate is formed in proteins after synthesis on the ribosome."
"T"
"gamma-Carboxyglutamate is formed in proteins after translation by carboxylation of glutamate residues. The vitamin K dependent reaction is important in a number of calcium-binding proteins, including prothrombin and other blood-clotting proteins, where binding of calcium to a region of the protein containing several gamma-carboxyglutamate residues close together is essential for biological activity."
45, blank.bmp
"Ornithine is incorporated into proteins during synthesis on the ribosome."
"F"
"Ornithine is an amino acid that is a metabolic intermediate in the synthesis of urea. It does not occur in proteins."
"Ornithine is formed in proteins after translation."
"F"
"Ornithine is an amino acid that is a metabolic intermediate in the synthesis of urea. It does not occur in proteins."
46, blank.bmp
"Citrulline is incorporated into proteins during synthesis on the ribosome."
"F"
"Citrulline is an amino acid that is a metabolic intermediate in the synthesis of urea. It does not occur in proteins."
"Citrulline is formed in proteins after translation."
"F"
"Citrulline is an amino acid that is a metabolic intermediate in the synthesis of urea. It does not occur in proteins."
47, blank.bmp
"Hydroxyproline is incorporated into proteins during synthesis on the ribosome."
"F"
"Hydroxyproline is formed by post-synthetic modification of the protein - proline residues in pro-collagen are hydroxylated in a vitamin C dependent reaction."
"Hydroxyproline is formed in proteins after translation."
"T"
"Hydroxyproline is formed by post-synthetic modification of the protein - proline residues in pro-collagen are hydroxylated in a vitamin C dependent reaction."
48, blank.bmp
"Hydroxylysine is incorporated into proteins during synthesis on the ribosome."
"F"
"Hydroxylysine is formed by post-synthetic modification of the protein - lysine residues in pro-collagen are hydroxylated in a vitamin C dependent reaction."
"Hydroxylysine is formed in proteins after translation."
"T"
"Hydroxylysine is formed by post-synthetic modification of the protein - lysine residues in pro-collagen are hydroxylated in a vitamin C dependent reaction."
49, DLaaO.bmp
"D-Amino acid oxidase in the kidney is important in amino acid metabolism."
"F"
"D-Amino acids are not part of normal metabolism at all. D-Amino acid oxidase is important for the metabolism, and hence detoxication, of the relatively small amounts of D-amino acids that enter the body from bacterial proteins."
"L-Amino acid oxidase in the liver is important in amino acid metabolism."
"F"
"Although L-amino acid oxidase in the liver will act on all the (naturally occurring) L-amino acids, it has very low activity and makes very little contribution to overall amino acid metabolism."
50, gludH.bmp
"Glutamate dehydrogenase catalyses either oxidative deamination of glutamate to ketoglutarate or the reductive formation of glutamate from ketoglutarate, depending on the concentration of ammonium in the cell."
"T"
"Glutamate dehydrogenase catalyses either oxidative deamination of glutamate to ketoglutarate or the reverse reaction, which is reductive amination of ketoglutarate to glutamate. The equilibrium of the reaction is delicately poised, so that the direction of the reaction depends largely on the concentration of ammonium in the cell."
"Although it acts only on glutamate, glutamate dehydrogenase is important in the deamination of most amino acids."
"T"
"The ketoglutarate formed by glutamate dehydrogenase can be converted back to glutamate by a number of transaminases that have different amino acid donors, so linkage of glutamate dehydrogenase and various transaminases provides a pathway for oxidative deamination of most amino acids."
51, glyox.bmp
"Glycine oxidase acts on all L-amino acids."
"F"
"Glycine oxidase acts specifically on glycine. Remember that glycine does not have a centre of asymmetry, since there are two H atoms attached to the alpha-carbon, and is therefore neither D- nor L-."
"Although it acts only on glycine, glycine oxdase is important in the deamination of most amino acids."
"T"
"The glyoxylate formed by glycine oxidase can be converted back to glycine by a number of transaminases that have different amino acid donors, so linkage of glycine oxidase and various transaminases provides a pathway for oxidative deamination of most amino acids."
52, gludH2.bmp
"When tissue concentrations of ammonium are high, glutamate dehydrogenase will deplete the pool of ketoglutarate, leading to impaired citric acid cycle activity."
"T"
"Although the formation of glutamate is considered to be a detoxication of ammonium, depletion of ketoglutarate and reduced citric acid cycle activity is probably the main mechanism to explain ammonia toxicity."
"Glutaminase in the kidney catalyses formation of ammonium to neutralize excessive acidic urine."
"T"
"The isoenzyme of glutaminase in the renal tubules is sensitive to the pH of the tubule contents, and as an excessively acidic urine is formed, so glutaminase catalyses hydrolysis of glutamine, forming ammonium to neutralize the acid."
53, serdeam.bmp
"Serine deaminase catalyses a non-oxidative deamination of serine to pyruvate."
"T"
"Unlike the oxidative deamination of glutamate and glycine, which yield keto-acids that can be converted back to the parent amino acid by transamination, the product of serine deaminase is pyruvate; transamination of pyruvate yields alanine, not serine."
"Serine deaminase catalyses oxidative deamination of serine to pyruvate."
"F"
"The reaction of serine deaminase does not involve oxidation. Unlike the oxidative deamination of glutamate and glycine, which yield keto-acids that can be converted back to the parent amino acid by transamination, the product of serine deaminase is pyruvate; transamination of pyruvate yields alanine, not serine."
54, DLaaO.bmp
"D-Amino acid oxidase in the kidney is important in detoxication of D-amino acids that come from bacterial proteins."
"T"
"D-Amino acids are not part of normal metabolism at all. D-Amino acid oxidase is important for the metabolism, and hence detoxication, of the relatively small amounts of D-amino acids that enter the body from bacterial proteins."
"There is a high activity of a general L-amino acid oxidase in the liver."
"F"
"L-Amino acid oxidase in the liver has a very low activity. Therefore it is not particularly important in amino acid metabolism."
55, gln.bmp
"Synthesis of glutamine in peripheral tissues is a mechanism for detoxication of ammonia."
"T"
"Glutamine has a major role in the transport of ammonium from peripheral tissues to the liver and kidneys."
"Glutamine can be hydrolysed to yield ammonium in the kidney."
"T"
"The isoenzyme of glutaminase in the renal tubules is sensitive to the pH of the tubule contents, and as an excessively acidic urine is formed, so glutaminase catalyses hydrolysis of glutamine, forming ammonium to neutralize the acid."
56, gln.bmp
"Glutamine has two amino groups."
"F"
"The side-chain of glutamine contains an amide group, not an amino group."
"Glutamine is a basic amino acid."
"F"
"The side-chain of glutamine contains an amide group, which is neutral, not a (basic) amino group."
57, asn.bmp
"Asparagine has two amino groups."
"F"
"The side-chain of asparagine contains an amide group, not an amino group."
"Asparagine is a basic amino acid."
"F"
"The side-chain of asparagine contains an amide group, which is neutral, not a (basic) amino group."
58, gln.bmp
"Glutamine is a nitrogen donor in a number of synthetic reactions."
"T"
"Glutamine provides nitrogen in a wide variety of synthetic reactions, especially in the synthesis of purines and pyrimidines."
"Glutamine provides much of the ammonium for urea synthesis in the liver."
"T"
"One nitrogen in urea comes from ammonium, and the other from aspartate. About half the ammonium is probably formed by hydrolysis of glutamine, and the rest by the action of adenine deaminase."
59, transam.bmp
"Glutamine is transaminated to keto-glutarate."
"F"
"Transamination involves the amino group attached to the alpha-carbon of an amino acid; although glutamine does undergo transamination, the product is not ketoglutarate. In order to form ketoglutarate from glutamine it would first have to undergo hydrolysis of the amide group, catalysed by glutaminase, yielding glutamate, which can then be transaminated to ketoglutarate."
"Asparagine is transaminated to oxaloacetate."
"F"
"Transamination involves the amino group attached to the alpha-carbon of an amino acid; although asparagine does undergo transamination, the product is not oxaloacetate. In order to form oxaloacetate from asparagine it would first have to undergo hydrolysis of the amide group, catalysed by asparaginase, yielding aspartate, which can then be transaminated to oxaloacetate."
59, transam.bmp
"Aspartate is transaminated to oxaloacetate."
"T"
"The keto-acid carbon skeleton of aspartate is indeed oxaloacetate."
"Glutamate is transaminated to oxaloacetate."
"F"
"The keto-acid carbon skeleton of glutamate is ketoglutarate. Oxaloacetate is the keto-acid corresponding to aspartate."
60, transam.bmp
"Aspartate is transaminated to ketoglutarate."
"F"
"The keto-acid carbon skeleton of aspartate is oxaloacetate. Ketoglutarate is the keto-acid corresponding to glutamate."
"Glutamate is transaminated to pyruvate."
"F"
"The keto-acid carbon skeleton of glutamate is ketoglutarate. Pyruvate is the keto-acid corresponding to alanine."
61, transam.bmp
"Transaminases form ammonium from amino acids."
"F"
"Transaminases transfer the amino group from an amino acid onto an acceptor keto-acid; free ammonium is not formed in transamination reactions."
"Transaminases are involved in the catabolism of most amino acids. 
"T"
"With the exception of lysine, all amino acids can undergo transamination, and the resultant keto-acids enter central metabolic pathways. However, transamination is not the major fate of all amino acids - for example, phenylalanine is normally hydroxylated to tyrosine, not transaminated."
62, transam.bmp
"The transamination of an amino acid yields a carbon skeleton that may be used for gluconeogenesis or ketone body synthesis, depending on the amino acid."
"T"
"Most amino acids yield carbon skeletons that can be used completely or partially for gluconeogenesis. Some yield both glucogenic and ketogenic fragments, and two are purely ketogenic, since they yield acetyl CoA and / or acetoacetyl CoA."
"Transaminases provide the main pathway for channelling the amino groups of amino acids into ammonium ions, by linking to glycine oxidase or glutamate dehydrogenase."
"T"
"There is a wide variety of transaminases in tissues, many of which are linked, directly or indirectly, to ketoglutarate or glyoxylate as the amino acceptor."
63, transam.bmp
"Pyridoxal phosphate (vitamin B6) is the coenzyme for transaminases."
"T"
"Pyridoxal phosphate at the active site of transaminases acts as an intermediate carrier of the amino group, forming pyridoxamine phosphate by reaction with the donor amino acid, then donating the amino group to the acceptor keto acid."
"Thiamin diphosphate (vitamin B1) is the coenzyme for transaminases."
"F"
"Pyridoxal phosphate, which is vitamin B6, at the active site of transaminases acts as an intermediate carrier of the amino group, forming pyridoxamine phosphate by reaction with the donor amino acid, then donating the amino group to the acceptor keto acid."
64, transam.bmp
"Riboflavin phosphate (vitamin B2) is the coenzyme for transaminases."
"F"
"Pyridoxal phosphate, which is vitamin B6, at the active site of transaminases acts as an intermediate carrier of the amino group, forming pyridoxamine phosphate by reaction with the donor amino acid, then donating the amino group to the acceptor keto acid."
"Vitamin B12 is the coenzyme for transaminases."
"F"
"Pyridoxal phosphate, which is vitamin B6, at the active site of transaminases acts as an intermediate carrier of the amino group, forming pyridoxamine phosphate by reaction with the donor amino acid, then donating the amino group to the acceptor keto acid."
65, transam.bmp
"The reaction of a transaminase follows a ping pong mechanism."
"T"
"Transaminases provide an excellent example of a ping pong mechanism in which the enzyme (or in this case the coenzyme bound at the active site) undergoes a chemical modification (it accepts the amino group from the amino acid substrate, forming pyridoxamine phosphate) in the first half of the reaction, then undergoes the reverse modification in the second half, when it transfers the amino group to the acceptor keto-acid, leaving pyridoxal phosphate at the active site again."
"The reaction of a transaminase follows an ordered mechanism."
"F"
"Transaminases follow a ping pong mechanism in which the enzyme (or in this case the coenzyme bound at the active site) undergoes a chemical modification (it accepts the amino group from the amino acid substrate, forming pyridoxamine phosphate) in the first half of the reaction, then undergoes the reverse modification in the second half, when it transfers the amino group to the acceptor keto-acid, leaving pyridoxal phosphate at the active site again."
66, transam.bmp
"The transamination of all amino acids yields a carbon skeleton that can be used for gluconeogenesis."
"F"
"Most amino acids yield carbon skeletons that can be used completely or partially for gluconeogenesis. Some yield both glucogenic and ketogenic fragments, and two are purely ketogenic, since they yield acetyl CoA and / or acetoacetyl CoA."
"The transamination of all amino acids yields a carbon skeleton that is a substrate for ketogenesis."
"F"
"Most amino acids yield carbon skeletons that can be used completely or partially for gluconeogenesis. Some yield both glucogenic and ketogenic fragments, and two are purely ketogenic, since they yield acetyl CoA and / or acetoacetyl CoA."
67, DLaaO.bmp
"The keto- (oxo-) acid formed from a D-amino acid by the action of D-amino acid oxidase can be a substrate for transamination to the L-amino acid."
"T" 
"Because the keto-acid formed from an amino acid by D-amino acid oxidase does not have a centre of asymmetry, it will be a substrate for transamination, and the product will be the L-amino acid. This means that there is at least a limited capacity to metabolize and utilize D-amino acids."
"D-Amino acids that come from bacterial proteins can be utilized to some extent."
"T"
"Because the keto-acid formed from an amino acid by D-amino acid oxidase does not have a centre of asymmetry, it will be a substrate for transamination, and the product will be the L-amino acid. This means that there is at least a limited capacity to metabolize and utilize D-amino acids."
68, transam1.bmp
"The diagram shows the reaction of a transaminase. Compound A is the donor amino acid."
"T"
"This is the amino acid that donates its amino group in the reaction."
"The diagram shows the reaction of a transaminase. Compound B is the product amino acid."
"F"
"Compound B is a keto-acid, not an amino acid. It is formed when compound A donates its amino group to the enzyme."
69, transam1.bmp
"The diagram shows the reaction of a transaminase. Compound C is the acceptor keto-acid."
"T"
"This is the keto acid that accepts the amino group."
"The diagram shows the reaction of a transaminase. Compound D is the product keto-acid."
"F"
"Compound D is an amino acid, not a keto-acid. It is formed when C accepts the amino group from the enzyme."
70, transam1.bmp
"The diagram shows the reaction of a transaminase. If substrate A is labelled with [14C], the label will be found in product D."
"F"
"Product D is the amino acid formed by transfer of the amino group from substrate A onto substrate C. The carbon skeleton of amino acid A is product B, so this is where the label would be found."
"The diagram shows the reaction of a transaminase. If substrate A is labelled with [14C], the label will be found in product B."
"T"
"Product B is the keto- acid formed when substrate C accepts the amino group from substrate A, so this is where the label would from substrate A will be found."
71, transam.bmp
"The diagram shows the reaction of a transaminase. If substrate C is labelled with [14C], the label will be found in product B."
"F"
"Product B is the amino acid formed by transfer of the amino group from substrate A onto substrate C. Therefore the label from substrate C would be found in product D."
"The diagram shows the reaction of a transaminase. If substrate C is labelled with [14C], the label will be found in product D."
"T"
"Product D is the amino acid formed when substrate C accepts the amino group from substrate A, so this is where the label would from substrate C will be found."
72, transam1.bmp
"The diagram shows the reaction of a transaminase. If compound A is labelled with [15N], the label will be found in compound D."
"T"
"Compound A is the donor amino acid, and the amino group, which will be labelled with [15N] is transferred to compound C, forming compound D, so this is where the label will be found."
"The diagram shows the reaction of a transaminase. If compound A is labelled with [15N], the label will be found in compound B."
"F"
"Compound B is the keto-acid formed when the amino group, which contains the [15N], is transferred onto compound C; it has no nitrogen, and therefore will not be labelled with [15N]. The label will be found in compound D, which is formed when compound C accepts the amino group."
73, transam1.bmp
"The diagram shows the reaction of a transaminase. If compound D is labelled with [15N], some label will be found in compound A."
"T"
"Transaminases are readily reversible, and therefore although the reaction is shown as going from A + C to form B + D, there will also be formation of A and C from B + D. Therefore if [15N] labelled D is added to the incubation some label will indeed be found in compound A."
"The diagram shows the reaction of a transaminase. If compound D is labelled with [15N], some label will be found in compound A."
"T"
"Transaminases are readily reversible, and therefore although the reaction is shown as going from A + C to form B + D, there will also be formation of A and C from B + D. Therefore if [15N] labelled D is added to the incubation some label will indeed be found in compound A."
74, transam1.bmp
"The diagram shows the reaction of a transaminase. In the first stage of the reaction an amino group is transferred from compound A onto the coenzyme, forming pyridoxamine phosphate at the active site."
"T"
"The first half of a transaminase reaction is transfer of the amino group from the donor amino acid (A in this diagram) onto the coenzyme, forming pyridoxamine phosphate."
"The diagram shows the reaction of a transaminase. In the first stage of the reaction an amino group is transferred from pyridoxamine phosphate at the active site onto compound C, to form compound D."
"F"
"The first half of a transaminase reaction is transfer of the amino group from the donor amino acid (A in this diagram) onto the coenzyme, forming pyridoxamine phosphate. Transfer of the amino group from the coenzyme to the acceptor keto-acid (C in this diagram) is the second half of the reaction."
75, transam1.bmp
"The diagram shows the reaction of a transaminase. In the second stage of the reaction an amino group is transferred from pyridoxamine phosphate at the active site onto compound C, to form compound D."
"T"
"Transfer of the amino group from the coenzyme to the acceptor keto-acid (C in this diagram) is the second half of the reaction."
"The diagram shows the reaction of a transaminase. In the second stage of the reaction an amino group is transferred from compound A onto the coenzyme, forming pyridoxamine phosphate at the active site."
"F"
"The first half of a transaminase reaction is transfer of the amino group from the donor amino acid (A in this diagram) onto the coenzyme, forming pyridoxamine phosphate. Transfer of the amino group from the coenzyme to the acceptor keto-acid (C in this diagram) is the second half of the reaction."
76, transdeam1.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glycine oxidase."
"F"
"Glycine does not appear in the reaction sequence shown here; enzyme B is glutamate dehydrogenase."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glutamate dehydrogenase."
"T"
"This is glutamate dehydrogenase - it catalyses the oxidative deamination of glutamate to ketoglutarate."
77, transdeam2.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glycine oxidase."
"T"
"This is glycine oxidase - it catalyses the oxidative deamination of glycine to glyoxylate."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glutamate dehydrogenase."
"F"
"Glutamate does not appear in the reaction sequence shown here; enzyme B is glycine oxidase."
78, transdeam1.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If the amino acid substrate is labelled with [14C] the label will be found in ketoglutarate."
"F"
"The amino group of the amino acid substrate is transferred onto ketoglutarate to form glutamate, but the carbon skeleton of the amino acid substrate (which is what will be labelled with [14C]) becomes the keto-acid product, so this is where the [14C] label will be found."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If the amino acid substrate is labelled with [15N] some label will be found in glutamate."
"T"
"The amino group from the amino acid substrate is transferred onto ketoglutarate to form glutamate, so this is where some of the [15N] label will be found, although most will appear in ammonium."
79, transdeam2.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If the amino acid substrate is labelled with [14C] the label will be found in glyoxylate."
"F"
"The amino group of the amino acid substrate is transferred onto glyoxylate to form glycine, but the carbon skeleton of the amino acid substrate (which is what will be labelled with [14C]) becomes the keto-acid product, so this is where the [14C] label will be found."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If the amino acid substrate is labelled with [15N] some label will be found in glycine."
"T"
"The amino group from the amino acid substrate is transferred onto glyoxylate to form glycine, so this is where some of the [15N] label will be found, although most will appear in ammonium."
80, transdeam1.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glutamine synthetase."
"F"
"Glutamine does not appear in this reaction sequence. Enzyme B is glutamate dehydrogenase."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Enzyme B is glutaminase."
"F"
"Glutamine does not appear in this reaction sequence. Enzyme B is glutamate dehydrogenase."
81, transdeam2.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. Because enzyme B produces hydrogen peroxide, it is found in the peroxisomes, together with catalase and peroxidases."
"T"
"As part of the body's protection against the effects of oxygen radicals, enzymes that produce hydrogen peroxide are compartmentalized in peroxisomes together with catalase and peroxidases that reduce the hydrogen peroxide to water."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If cells are incubated with [15N] labelled ammonium some of the label will be found in a wide variety of amino acids."
"F"
"The reaction catalysed by enzyme B, glycine oxidase, is not readily reversible, and therefore this reaction sequence is not overall reversible."
82, transdeam1.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If cells are incubated with [15N] labelled ammonium some of the label will be found in a wide variety of amino acids."
"T"
"The reaction catalysed by glutamate dehydrogenase is readily reversible, and the position of the equilibrium depends on the relative concentrations of the various substrates. When ammonium concentrations are high, there will be nett incorporation of ammonium into glutamate, and then a variety of other amino acids, so that label from [15N] ammonium will be found in various amino acids."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. If cells are incubated with [15N] labelled ammonium some of the label will be found in a wide variety of amino acids."
"T"
"The reaction catalysed by glutamate dehydrogenase is readily reversible, and the position of the equilibrium depends on the relative concentrations of the various substrates. When ammonium concentrations are high, there will be nett incorporation of ammonium into glutamate, and then a variety of other amino acids, so that label from [15N] ammonium will be found in various amino acids."
83, transdeam2.bmp
"The diagram shows a pathway for the overall deamination of a variety of amino acids. A genetic defect in enzyme A is the cause of one type of primary hyperoxaluria."
"T"
"Enzyme A is alanine glyoxylate transaminase; if this enzyme has impaired activity then glyoxylate cannot be transaminated back to glycine to continue the cycle, but will accumulate and undergo reduction to oxalate."
"The diagram shows a pathway for the overall deamination of a variety of amino acids. A genetic defect resulting in the targetting of enzyme A into mitochondria rather than peroxisomes is the cause of one type of primary hyperoxaluria."
"T"
"Glycine oxidase (enzyme B) is a peroxisomal enzyme. Enzyme A is alanine glyoxylate transaminase; if this enzyme is targeted to mitochondria rather than peroxisomes, as occurs with some mutations in the gene for this enzyme, then glyoxylate formed in the peroxisomes cannot be transaminated back to glycine to continue the cycle, but will accumulate and undergo reduction to oxalate."
84, blank.bmp
"Urea is a non-essential amino acid."
"F"
"Urea is not an amino acid."
"High concentrations of urea in the bloodstream lead to the development of gout."
"F"
"Gout is due to accumulation of uric acid in blood and tissues, not urea. Uric acid has nothing to do with urea. Both are end-products of nitrogen metabolism, and both are excreted in the urine (hence the similarity of their names)."
84, blank.bmp
"Carbamyl phosphate is a precursor for synthesis of both urea and pyrimidines."
"T"
"Different isoenzymes of carbamyl phosphate synthetase, in different cell compartments, and under very different metabolic control, are involved in these two pathways."
"Carbamyl phosphate that is not required for pyrimidine synthesis is a substrate for urea synthesis."
"F"
"Different isoenzymes of carbamyl phosphate synthetase, in different cell compartments, and under very different metabolic control, are involved in these two pathways."
85, arg.bmp
"Arginine is synthesized in the kidney by the same pathway as is used in the liver for synthesis of urea."
"T"
"Although kidney cannot hydrolyse arginine to ornithine and urea, since it lacks arginase, it does contain the other enzymes of the pathway, and the kidney is probably the major source of arginine in the body."
"Arginine synthesized in the liver is transported to the kidneys where it is hydrolysed to yield urea and ornithine."
"F"
"The hydrolysis of arginine to yield urea and ornithine occurs in the liver. Although the kidney can synthesize arginine, it cannot catalyse the hydrolysis of arginine to urea and ornithine."
86, blank.bmp
"Argininosuccinic acid is formed by reaction between arginine and succinyl CoA."
"F"
"Argininosuccinic acid is formed by reaction between citrulline and aspartate."
"Urea is a major metabolic fuel in the kidney."
"F"
"Urea is a metabolic end-product."
87, blank.bmp
"The amount of urea excreted varies with protein intake."
"T"
"Because urea is the main end-product of amino acid metabolism, the amount excreted reflects the total amount of amino acids (i.e. protein) being catabolised."
"Uric acid is a precursor for urea synthesis."
"F"
"Uric acid has nothing to do with urea. Both are end-products of nitrogen metabolism, and both are excreted in the urine (hence the similarity of their names)."
88, blank.bmp
"Carbamyl phosphate synthetase for urea synthesis is only active in the presence of N-acetyl glutamate."
"T"
"In turn, N-acetyl glutamate is an intermediate in the synthesis of ornithine. This obligatory activation of carbamyl phosphate synthetase by N-acetyl glutamate thus ensures that ammonia will only enter the pathway of urea formation when there is an adequate amount of ornithine available."
"Urea is hydrolysed to ammonium in the kidney tubules."
"F"
"There is no mammalian enzyme that catalyses the hydrolysis of urea. However, intestinal bacterial enzymes hydrolyse urea to ammonium and carbon dioxide, and much of the ammonium is reabsorbed and incorporated into amino acids, initially by way of reversal of the reaction of glutamate dehydrogenase in the liver, followed by transamination of the resultant glutamate to yield a variety of amino acids."
89, blank.bmp
"Urea is hydrolysed to ammonium in the intestinal lumen."
"T"
"There is considerable cycling of urea through the intestine, with hydrolysis by intestinal bacterial urease to yield ammonium and carbon dioxide. Much of the ammonium is reabsorbed and incorporated into amino acids, initially by way of reversal of the reaction of glutamate dehydrogenase in the liver, followed by transamination of the resultant glutamate to yield a variety of amino acids."
"If subjects are given [15N] labelled urea intravenously, the label will appear in a number of amino acids."
"T"
"There is considerable cycling of urea through the intestine, with hydrolysis by intestinal bacterial urease to yield ammonium and carbon dioxide. Much of the ammonium is reabsorbed and incorporated into amino acids, initially by way of reversal of the reaction of glutamate dehydrogenase in the liver, followed by transamination of the resultant glutamate to yield a variety of amino acids."
90, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. Line A represents the incubations with the highest concentration of arginine."
"F"
"Arginine increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of arginine."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. Line D represents the incubations with the highest concentration of arginine."
"T"
"Arginine increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of arginine."
91, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. Line A represents the incubations with the highest concentration of citrulline."
"F"
"Citrulline increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of citrulline."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. Line D represents the incubations with the highest concentration of citrulline."
"T"
"Citrulline increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of citrulline."
92, orn.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of ornithine. Line A represents the incubations with the highest concentration of ornithine."
"F"
"Ornithine increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of ornithine."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of ornithine. Line D represents the incubations with the highest concentration of ornithine."
"T"
"Ornithine increases the rate of formation of urea, so line D must represent the incubations with the highest concentration of ornithine."
93, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. With no added ammonium there is formation of ~1 mol of urea per mol of arginine added."
"T"
"You would expect to see 1 mol of urea formed per mol of arginine added, since hydrolysis of arginine by arginase yields urea and ornithine."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. With no added ammonium there is formation of ~1 mol of urea per mol of citrulline added."
"T"
"Citrulline can be converted to arginine via the formation of argininosuccinic acid, and you would expect to see 1 mol of urea formed per mol of citrulline added, since hydrolysis of arginine by arginase yields urea and ornithine."
94, orn.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of ornithine. With no added ammonium there is formation of ~1 mol of urea per mol of ornithine added."
"F"
"With no added ammonium there is no urea formed regardless of how much ornithine is added. There is no direct formation of urea from ornithine. If there is no ammonium available then there will be little or no formation of carbamyl phosphate, and hence the ornithine will accumulate rather than being metabolized. In the absence of ammonium there can be no formation of urea from aspartate once the small amount of preformed citrulline in the cell has been exhausted."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of ornithine. With no added ammonium there is no formation of urea when ornithine is added."
"T"
"With no added ammonium there is no urea formed regardless of how much ornithine is added. There is no direct formation of urea from ornithine. If there is no ammonium available then there will be little or no formation of carbamyl phosphate, and hence the ornithine will accumulate rather than being metabolized. In the absence of ammonium there can be no formation of urea from aspartate once the small amount of preformed citrulline in the cell has been exhausted."
95, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. At a saturating concentration of ammonium there is very much more than 1 mol of urea formed per mol of arginine added."
"T"
"You would expect to see 1 mol of urea formed per mol of arginine added, since hydrolysis of arginine by arginase yields urea and ornithine. However, the ornithine formed increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of very much more urea than might be expected."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. At a saturating concentration of ammonium there is very much more than 1 mol of urea formed per mol of citrulline added."
"T"
"Ornithine increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of much more urea than might be expected."
96, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. At a saturating concentration of ammonium very much more than 1 mol of ammonium is consumed per mol of arginine added."
"T"
"You would expect to see 1 mol of urea formed per mol of arginine added, since hydrolysis of arginine by arginase yields urea and ornithine. However, the ornithine formed increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of much more urea than might be expected."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of arginine. At a saturating concentration of ammonium very much less than 1 mol of ammonium is consumed per mol of arginine added."
"F"
"There is more ammonium consumed, and more urea formed than you might expect when you add arginine. You would expect to see 1 mol of urea formed per mol of arginine added, since hydrolysis of arginine by arginase yields urea and ornithine. However, the ornithine formed increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of much more urea than might be expected."
97, argcit.bmp
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. At a saturating concentration of ammonium very much more than 1 mol of ammonium is consumed per mol of citrulline added."
"T"
"Citrulline increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of much more urea than might be expected."
"The diagram shows the formation of urea by isolated liver cells incubated with varying concentrations of ammonium and either no other addition or three different concentrations of citrulline. At a saturating concentration of ammonium very much less than 1 mol of ammonium is consumed per mol of citrulline added."
"F"
"There is more ammonium consumed, and more urea formed than you might expect when you add citrulline. 
Citrulline increases the cell pool of the intermediates of the urea synthesis cycle, and so permits faster metabolism of ammonia, and the formation of much more urea than might be expected."
98, halflife.bmp
"The diagram shows the labelling a plasma protein over several days after giving a dose of [15N] labelled glycine. There is a decrease in the labelling of the protein because of radioactive decay of the [15N]."
"F"
"[15N] is a stable isotope, not radioactive, and therefore does not decay. The decrease in labelling of the protein is because of turnover of the protein - catabolism and replacement synthesis from amino acids that do not now include a significant amount of [15N] glycine."
"The diagram shows the labelling a plasma protein over several days after giving a dose of [15N] labelled glycine. There is a decrease in the labelling of the protein because of turnover of the protein."
"T"
"As the labelled protein that was synthesized when the dose of [15N] glycine was given is catabolized, it is replaced by newly synthesized protein - and there is now not a significant amount of [15N] glycine to be incorporated into the newly synthesized protein."
99, halflife.bmp
"The diagram shows the labelling a plasma protein over several days after giving a dose of [15N] labelled glycine. This curve can be used to estimate the rate of turnover of the protein."
"T"
"The rate at which the label is lost from the protein is determined by the rate at which the protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. Therefore this curve can indeed be used to estimate the rate of turnover of the protein."
"The diagram shows the labelling a plasma protein over several days after giving a dose of [15N] labelled glycine. The point labelled A is the half-life of the protein."
"T"
"The rate at which the label is lost from the protein is determined by the rate at which the protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The half-life of the protein is the time for the label to fall to half its maximum value; this is indeed point A."
100, halflives.bmp
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein A has the longest half-life."
"F" 
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The half-life of the protein is the time for the label to fall to half its maximum value. Protein A has the shortest half-life."
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein C has the longest half-life."
"T" 
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The half-life of the protein is the time for the label to fall to half its maximum value. Protein C has the longest half-life."
101, halfllives.bmp
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein A is synthesized most rapidly."
"T"
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The label is lost most rapidly from protein A, so this must be the protein with the most rapid rate of catabolism and replacement synthesis."
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein C is synthesized most rapidly."
"F"
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The label is lost most rapidly from protein A, so this must be the protein with the most rapid rate of catabolism and replacement synthesis."
102, halflives.bmp
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein A is catabolized most rapidly."
"T"
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The label is lost most rapidly from protein A, so this must be the protein with the most rapid rate of catabolism and replacement synthesis."
"The diagram shows the labelling of three different plasma proteins over several days after giving a dose of [15N] labelled glycine. Protein C is catabolized most rapidly."
"F"
"The rate at which the label is lost from a protein is determined by the rate at which that protein is catabolized and replaced by newly synthesized protein (from amino acids that will not now include a significant amount of [15N] glycine. The label is lost most rapidly from protein A, so this must be the protein with the most rapid rate of catabolism and replacement synthesis."
103, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week A their protein intake must have been at least equal to their requirement."
"T"
"In week A they were maintaining nitrogen balance, so their intake must have been equal to, or greater than, their requirement. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose protein intake was varied each week. In week A their protein intake was lower than their requirement."
"F"
"In week A they were maintaining nitrogen balance, so their intake must have been equal to, or greater than, their requirement. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
104, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week B their protein intake must have been at least equal to their requirement."
"F"
"In week B they were in severe negative nitrogen balance, so their protein intake must have been very much less than their requirement."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week B their protein intake must have been very much less than their requirement."
"T"
"In week B they were in severe negative nitrogen balance, so their protein intake must have been very much less than their requirement."
105, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week C their protein intake must have been at least equal to their requirement."
"F"
"In week C they were in negative nitrogen balance, although not as severe as in week B, so their protein intake must still have been very less than their requirement."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week C their protein intake must have been less than their requirement."
"T"
"In week C they were in negative nitrogen balance, although not as severe as in week B, so their protein intake must still have been very less than their requirement."
106, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week D their protein intake must have been only just equal to their requirement."
"T"
"In week D they were just able to maintain nitrogen balance, so their protein intake must have been adequate to maintain balance. However, this followed 2 weeks of negative nitrogen balance (weeks B and C), during which they will have lost a significant amount of body protein. They did not replace this during week D, so their intake must have been only just adequate to meet requirements."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week D their protein intake must have greater than their requirement."
"F"
"In week D they were just able to maintain nitrogen balance, so their protein intake must have been adequate to maintain balance. However, this followed 2 weeks of negative nitrogen balance (weeks B and C), during which they will have lost a significant amount of body protein. They did not replace this during week D, so their intake must have been only just adequate to meet requirements."
107, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week E their protein intake must have been only just equal to their requirement."
"F"
"In week E they were in positive nitrogen balance, replacing the protein lost during the two weeks of negative balance (weeks B and C). Therefore their intake must have been greater than the requirement to maintain balance, so that they were able to synthesize more protein than was being turned over and so replace the losses."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week E their protein intake must have been greater than their requirement."
"T"
"In week E they were in positive nitrogen balance, replacing the protein lost during the two weeks of negative balance (weeks B and C). Therefore their intake must have been greater than the requirement to maintain balance, so that they were able to synthesize more protein than was being turned over and so replace the losses."
108, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week F their protein intake must have been only just equal to their requirement."
"F"
"At the beginning of week F they were in positive nitrogen balance, replacing the protein lost during the two weeks of negative balance (weeks B and C). Therefore their intake must have been greater than the requirement to maintain balance, so that they were able to synthesize more protein than was being turned over and so replace the losses. Once they had replaced the lost protein (about half way through the week) they returned to balance. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week F their protein intake must have been greater than their requirement."
"T"
"At the beginning of week F they were in positive nitrogen balance, replacing the protein lost during the two weeks of negative balance (weeks B and C). Therefore their intake must have been greater than the requirement to maintain balance, so that they were able to synthesize more protein than was being turned over and so replace the losses. Once they had replaced the lost protein (about half way through the week) they returned to balance. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
109, nbal.bmp
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week G their protein intake must have been less than their requirement."
"F"
"They were able to maintain nitrogen balance in week G, so their intake must have been at least as great as their requirement, if not higher. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
"The diagram shows daily nitrogen balance over 7 weeks in a group of subjects whose total protein intake was varied each week. In week G their protein intake must have been at least equal to their requirement."
"T"
"They were able to maintain nitrogen balance in week G, so their intake must have been at least as great as their requirement, if not higher. Remember that except in growth or replacement of losses, zero balance can be maintained at any level of intake greater than requirements."
110, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no leucine."
"T"
"Leucine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no leucine."
"F"
"They were in positive nitrogen balance in week E. Leucine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
111, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no isoleucine."
"T"
"Isoleucine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no isoleucine."
"F"
"They were in positive nitrogen balance in week E. Isloeucine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
112, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no valine."
"T"
"Valine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no valine."
"F"
"They were in positive nitrogen balance in week E. Valine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
113, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no tryptophan."
"T"
"Tryptophan is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no tryptophan."
"F"
"They were in positive nitrogen balance in week E. Tryptophan is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
114, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no phenylalanine."
"T"
"Phenylalanine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no phenylalanine."
"F"
"They were in positive nitrogen balance in week E. Phenylalanine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
115, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no methionine."
"T"
"Methionine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no methionine."
"F"
"They were in positive nitrogen balance in week E. Methionine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
115, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no threonine."
"T"
"Threonine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no threonine."
"F"
"They were in positive nitrogen balance in week E. Threonine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
116, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no lysine."
"T"
"Lysine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week E the mixture could have contained no lysine."
"F"
"They were in positive nitrogen balance in week E. Lysine is an essential amino acid, and therefore if it is omitted from the diet it is not possible to maintain nitrogen balance and the subjects would show severely negative nitrogen balance."
117, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no glutamate."
"F"
"Glutamate is a non-essential amino acid, and can be synthesized in adequate amounts from the common metabolic intermediate ketoglutarate. Therefore it would still be possible to maintain nitrogen balance on a glutamate-free diet."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no aspartate."
"F"
"Aspartate is a non-essential amino acid, and can be synthesized in adequate amounts from the common metabolic intermediate oxaloacetate. Therefore it would still be possible to maintain nitrogen balance on an aspartate-free diet."
118, nbal.bmp
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no alanine."
"F"
"Alanine is a non-essential amino acid, and can be synthesized in adequate amounts from the common metabolic intermediate pyruvate. Therefore it would still be possible to maintain nitrogen balance on an alanine-free diet."
"The diagram shows daily nitrogen balance in a group of subjects who were fed mixtures of amino acids designed to provide an adequate amount of total protein, but whose composition was changed each week. In week B the mixture could have contained no alanine."
"F"
"Alanine is a non-essential amino acid, and can be synthesized in adequate amounts from the common metabolic intermediate pyruvate. Therefore it would still be possible to maintain nitrogen balance on an alanine-free diet."
119, blank.bmp
"In general, proteins with a short half-life (ie a rapid turnover) are those that have a role in regulating the activity of metabolic pathways."
"T"
"One of the mechanisms of metabolic control is to change the amount of enzyme in the cell, and for this to be effective in a reasonable time it is essential that the enzyme concerned has a rapid turnover."
"An enzyme that has a rapid turnover (ie a short half-life) is likely to be one that has a role in regulating the activity of a metabolic pathway."
"T"
"One of the mechanisms of metabolic control is to change the amount of enzyme in the cell, and for this to be effective in a reasonable time it is essential that the enzyme concerned has a rapid turnover."
120, blank.bmp
"All the proteins in a cell turn over at the same rate."
"F"
"There is a wide range of rates of turnover of different proteins in any one cell, or indeed one sub-cellular compartment."
"All the proteins in a cell have the same half-life."
"F"
"There is a wide range of half-lives of different proteins in any one cell, or indeed one sub-cellular compartment."
121, gln.bmp
"Glutamine is an essential amino acid."
"F"
"Glutamine is not an essential amino acids. However, under some conditions the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
"There may be a requirement for a dietary intake of glutamine (which is not an essential amino acid) after surgical trauma and in sepsis."
"T"
"Glutamine is not an essential amino acids. However, under some conditions (eg after surgical trauma and in sepsis) the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
122, arg.bmp
"Arginine is an essential amino acid."
"F"
"Arginine is not an essential amino acids. However, under some conditions the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
"There may be a requirement for a dietary intake of arginine (which is not an essential amino acid) at times of rapid growth."
"T"
"Arginine is not an essential amino acids. However, under conditions of rapid growth the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
123, gly.bmp
"Glycine is an essential amino acid."
"F"
"Glycine is not an essential amino acids. However, under some conditions the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
"There may be a requirement for a dietary intake of glycine (which is not an essential amino acid) when there is a high intake of benzoic acid and other xenobiotics."
"T"
"Glycine is not an essential amino acids. However, when there is a high intake of benzoic acid and other xenobiotics that are excreted as glycine conjugates the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
124, pro.bmp
"Proline is an essential amino acid."
"F"
"Proline is not an essential amino acids. However, under some conditions the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
"There may be a requirement for a dietary intake of proline (which is not an essential amino acid) in response to severe trauma."
"T"
"Proline is not an essential amino acids. However, in response to severe trauma, when there is a considerable requirement for proline for collagen synthesis, the requirement may exceed the capacity to synthesize it, so that a dietary intake is required."
125, blank.bmp
"In response to infection, injury or surgical trauma there is a considerable loss of body protein; this catabolic loss may amount to as much as 6 - 7% of total body protein over 10 days. Because of this there is a need for a high protein diet in convalescence."
"F"
"Although convalescence involves replacement of the protein that was lost in response to trauma, average protein intakes are about twice as high as requirements, and therefore a normal protein intake will provide more than enough amino acids to permit replacement of the lost tissue protein."
"In response to infection, injury or surgical trauma there is a considerable loss of body protein; this catabolic loss may amount to as much as 6 - 7% of total body protein over 10 days. Because of this there is a need for a low protein diet in convalescence."
"F"
"Although convalescence involves replacement of the protein that was lost in response to trauma, average protein intakes are about twice as high as requirements, and therefore a normal protein intake will provide more than enough amino acids to permit replacement of the lost tissue protein. However, a low protein diet would not meet the requirement for replacement of lost tissue and would impair convalscence."
126, blank.bmp
"In response to infection, injury or surgical trauma there is a considerable loss of body protein; this catabolic loss may amount to as much as 6 - 7% of total body protein over 10 days. Much of this catabolic loss is caused by the synthesis of acute phase proteins rich in threonine and cysteine."
"T"
"Synthesis of acute phase proteins that are richer in threonine and cysteine than most tissue proteins depletes the tissue pool of these two amino acids, leaving an unbalanced mixture of amino acids that cannot be used for protein synthesis, but are used as energy-yielding substrates."
"In response to infection, injury or surgical trauma there is a considerable loss of body protein; this catabolic loss may amount to as much as 6 - 7% of total body protein over 10 days. This serves to mobilize amino acids ready for repair."
"F"
"There is nett negative nitrogen balance in response to trauma - the amino acids released from tissue protein breakdown are catabolized, not stored and used for repair."
127, blank.bmp
"Both strands of DNA are transcribed to form mRNA. 
"F"
"Only one strand is copied - the template strand."
"Only one strand of DNA is copied to form mRNA."
"T"
"Only one strand is copied - the template strand."
128, blank.bmp
"mRNA is synthesized on the ribosome."
"F"
"mRNA is synthesized in the nucleus - it is translated on the ribosome."
"mRNA synthesis involves base pairing to the template strand of DNA."
"T"
"Base pairing permits mRNA to be a high fidelity copy of the information in DNA."
129, blank.bmp
"The process of making an RNA copy of DNA is known as translation."
"F"
Translation is the process of translating the message of mRNA into a protein sequence. The process of making an RNA copy of DNA is transcription."
"The process of making an RNA copy of DNA is known as transcription."
"T"
"Transcription means writing across - writing a copy of the information in a region of DNA in a length of RNA."
130, blank.bmp
"A codon is a series of 3 bases in mRNA."
"T"
"This is the definition of a codon - a sequence of three bases in mRNA."
"Each codon codes for more than one amino acid."
"F"
"Each codon is specific for one single amino acid."
131, blank.bmp
"All the amino acids found in a protein have a codon. 
"F"
"There are a number of amino acids in proteins that are formed by post-synthetic modification of the protein, and do not have codons."
"More than one codon codes for most amino acids."
"T"
"There are 64 possible codons, and a need for only 21 (plus STOP codons); there are several codons for all amino acids apart from tryptophan and methionine, each of which only has one codon."
132, blank.bmp
"Amino acyl tRNA synthetases are specific for the tRNA, but not the amino acid that they bind. 
"F"
"Amino acyl tRNA synthetases are extremely specific for both the amino acid and the tRNA that they bind."
"Any base change in the coding region of DNA will lead to a change in the amino acid sequence of the gene product. 
"F"
"Because there are multiple codons for most of the amino acids, many changes in the coding region of DNA will lead to no change in the amino acid that is encoded."
133, blank.bmp
"A codon may be any combination of three out of four different bases."
"T"
"This means there are 64 possible codons."
"All 64 possible codons code for amino acids."
"F"
"Three of the codons code for termination of translation (the STOP codons)."
134, blank.bmp
"All proteins have an amino terminal methionine because initiation of protein synthesis occurs at AUG, the codon for methionine."
"F"
"Although translation begins with AUG, which is the codon for methionine, most proteins undergo post-synthetic modification, including removal of terminal regions of the peptide chain."
"In many cases a single tRNA will recognise more than one codon."
"T"
"There are more codons than there are different species of tRNA. In many cases the tRNA has a loose specificity for the third base of the codon, so that where several codons code for the same amino acid, a single tRNA can read several of them."
135, blank.bmp
"The STOP codons contain 4 bases."
"F"
"Like all other codons, the STOP codons consist of three bases."
"There is only one tRNA for each amino acid."
"F"
"There are several tRNA species for each amino acid, so as to allow for binding to the sometimes very different multiple codons for each amino acid. However, some tRNA species will recognise and bind to more than one codon."
136, blank.bmp
"The activation of an amino acid for protein synthesis involves the formation of a covalent bond between the carboxyl group of the amino acid and the 3'-terminal adenosine residue of transfer RNA (tRNA). This is an ATP-dependent step."
"T"
"Forming the bond between the amino acid and tRNA is indeed an ATP-requiring step."
"The anticodon is the region of mRNA that binds to tRNA. 
"F"
"The anticodon is the region of tRNA that recognises and binds to the codon on mRNA."
137, blank.bmp
"A polyribosome is an array of several ribosomes that are translating the same mRNA molecule simultaneously."
"T"
"Under the electron microscope it is possible to see ribosomes arranged in a line, along a molecule of mRNA that is being translated - this is a polysome."
"Only one ribosome can translate a molecule of mRNA at a time. 
"F"
"Under the electron microscope it is possible to see ribosomes arranged in a line, along a molecule of mRNA that is being translated - this is a polysome."
-999
Copyright David A Bender 2002

