Deck 26: Protein Metabolism

Question 1

The nitrogen-containing product of oxidative deamination is

A) ammonium ion
B) carbamoyl phosphate
C) isopentenyl pyrophosphate
D) FADH₂

Answer 1

ammonium ion

Question 2

The two nitrogen atoms in a urea molecule have as their biosynthetic source

A) two ammonium ions
B) two aspartate ions
C) an ammonium ion and an aspartate ion
D) two acetyl CoA molecules

Answer 2

an ammonium ion and an aspartate ion

Question 3

One of the reactants in a transamination reaction is

A) an amino acid
B) glycerol
C) ammonia
D) ammonium ion

Answer 3

an amino acid

Question 4

Amino acids with carbon "skeletons" that are degraded to pyruvate are classified as

A) glucogenic
B) ketogenic
C) both glucogenic and ketogenic
D) neither glucogenic nor ketogenic

Question 5

With a normal diet, the percentage of daily calories that come from proteins is about

A) 10 percent
B) 20 percent
C) 30 percent
D) 40 percent

Question 6

In the degradation of heme, which of the following substances is produced in the second step of the degradation process?

A) bilirubin
B) biliverdin
C) urobilin
D) molecular oxygen

Question 7

Which of the following statements concerning amino acid biosynthesis is incorrect?

A) Glutamate is one of the three amino acids produced by transamination of the appropriate alpha-keto acid.
B) The essential amino acids require seven to ten steps for biosynthesis in microorganisms.
C) All but six of the standard amino acids can be biosynthesized in the human body.
D) The nonessential amino acid tyrosine is obtained from the essential amino acid phenylalanine.

Question 8

The citric acid cycle and the urea cycle are "linked" through the substance

A) malate
B) fumarate
C) oxaloacetate
D) ornithine

Question 9

The dominant use for the amino acids of the amino acid pool is the synthesis of

A) protein
B) nonprotein nitrogen compounds
C) nonessential amino acids
D) pyruvate for energy production

Question 10

Which of the following statements concerning the degradation of amino acid carbon "skeletons" is correct?

A) Each of the 20 standard amino acids gives a different degradation product.
B) Each of the 20 standard amino acids gives the same degradation product.
C) All final degradation products are citric acid cycle intermediates.
D) Some, but not all, final degradation products are citric acid cycle intermediates.

Question 11

In the degradation of heme, which of the following substances is produced at the same time that carbon monoxide is produced?

A) bilirubin
B) biliverdin
C) urobilin
D) stercobilin

Question 12

A derivative of pyridoxine (vitamin B₆) is required as a coenzyme in

A) transamination
B) oxidative deamination
C) the urea cycle
D) carbamoyl phosphate formation

Question 13

Which of the following urea cycle intermediates is incorrectly characterized relative to its nitrogen content?

A) citrulline; N₃ molecule
B) arginine; N₄ molecule
C) ornithine; N₂ molecule
D) argininosuccinate; N₃ molecule

Question 14

One of the products in a transamination reaction is

A) a ketoacid
B) glycerol
C) ammonia
D) acetyl CoA

Question 15

The net overall effect of transamination reactions in the human body is to collect the amino groups from a variety of amino acids into a single compound, which is

A) a keto acid
B) an amino acid
C) acyl carrier protein
D) carbamoyl phosphate

Question 16

If aspartate is a reactant in a transamination reaction, one of the products of the reaction must be

A) alanine
B) oxaloacetate
C) asparagine
D) pyruvate

Question 17

In the urea cycle, the urea-producing step involves the reaction of water with

A) aspartate
B) arginine
C) argininosuccinate
D) carbamoyl phosphate

Question 18

As dietary protein materials leave the stomach, they

A) are approximately 50 percent free amino acids
B) are approximately 90 percent free amino acids
C) are a mixture of large polypeptides
D) have been denatured, but no peptide bond cleavage has occurred

Question 19

The "fuel" for the urea cycle is

A) ammonium ion
B) bicarbonate ion
C) carbamoyl phosphate
D) acetyl CoA

Question 20

The most abundant amino acid in the amino acid pool is

A) alanine
B) aspartate
C) cysteine
D) glutamate

Question 21

Amino acid metabolism differs from that of carbohydrates and triacylglycerols in that:

A) There is no storage form for amino acids in the body.
B) Amino acids cannot be used for energy production.
C) Amino acids cannot be converted to acetyl CoA.
D) More than one correct response.
E) No correct response.

Question 22

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Protein digestion begins in the stomach rather than the small intestine.
(2) In the second step of heme degradation, biliverdin is converted to bilirubin.
(3) In the oxidative deamination of glutamate, alpha-ketoglutarate is one of the products.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 23

Which of the following processes supplies amino acids to the amino acid pool?

A) protein digestion
B) protein turnover
C) amino acid biosynthesis
D) more than one correct response
E) no correct response

Question 24

Which of the following substances is a reactant in the formation of carbamoyl phosphate?

A) carbon dioxide
B) water
C) ATP
D) more than one correct response
E) no correct response

Question 25

Which of the following statements concerning the compound urea is incorrect?

A) It is a white solid in the pure state.
B) It is very soluble in water.
C) It gives urine its odor and color.
D) More than one correct response.
E) No correct response.

Question 26

Which of the following is a reactant in oxidative deamination?

A) water
B) ammonium ion
C) NADH
D) more than one correct response
E) no correct response

Question 27

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) The net effect of protein digestion is the release of the protein's constituent amino acids.
(2) Ammonium ions enter the urea cycle in the form of carbamoyl phosphate.
(3) Glycogenic amino acids have carbon skeletons that are degraded to glucose.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 28

Bile pigments produced from the degradation of the heme portion of hemoglobin are responsible for

A) the yellow color of urine
B) the reddish-brown color of feces
C) the yellow skin color associated with the jaundice condition
D) more than one correct response
E) no correct response

Question 29

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Excess amino acids are stored in the body for later use in the form of tetra- and pentapeptides.
(2) The ultimate product of all transamination reactions is the amino acid glutamate.
(3) The oxygen atom in urea comes from a water molecule that participates in a hydrolysis reaction.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 30

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Citric acid cycle intermediates are often the products from amino acid carbon skeleton degradation.
(2) The net effect of transamination is to collect the amino groups from a variety of amino acids into the amino acids glutamate and aspartate.
(3) All of the reactions of the urea cycle occur within mitochondria.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 31

Substances to which amino acid carbon "skeletons" may be degraded include

A) acetyl CoA
B) citrate
C) succinate
D) more than one correct response
E) no correct response

Question 32

In the first step of the degradation of the heme portion of hemoglobin:

A) Molecular O₂ is needed as a reactant.
B) Carbon monoxide is a product.
C) Ring opening with the release of an iron atom occurs.
D) More than one correct response.
E) No correct response.

Question 33

A urea molecule contains

A) two nitrogen atoms
B) two carbon atoms
C) two hydrogen atoms
D) more than one correct response
E) no correct response

Question 34

Carbon-containing amino acid degradation products can be converted to

A) glucose
B) ketone bodies
C) fatty acids
D) more than one correct response
E) no correct response

Question 35

Which of the following is a product in oxidative deamination of glutamate?

A) oxaloacetate
B) water
C) pyruvate
D) more than one correct response
E) no correct response

Question 36

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Properties of the compound urea include yellow color, strong odor, and high solubility in water.
(2) The amino group acceptor in most transamination reactions is oxaloacetate.
(3) Absorption of amino acids through the intestinal wall requires active transport.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 37

Which of the following conversions could occur as part of a ansamination reaction?

A) pyruvate to alanine
B) alanine to pyruvate
C) oxaloacetate to glutamate
D) more than one correct response
E) no correct response

Question 38

Which of the following compounds is a urea cycle intermediate?

A) carbamoyl phosphate
B) aspartate
C) ornithine
D) more than one correct response
E) no correct response

Question 39

Which of the following substances is a possible reactant in a transamination reaction?

A) amino acid
B) secondary alcohol
C) saturated carboxylic acid
D) more than one correct response
E) no correct response

Question 40

The net effect of transamination is to

A) collect the amino groups from a variety of amino acids into a single compound
B) convert all nonessential amino acids into essential amino acids
C) convert all alpha-amino acids into beta-amino acids
D) more than one correct response
E) no correct response

Question 41

Use the following to answer the questions below:
For each of the urea cycle characterizations, select a correct response from the response list. Responses may be used more than once or need not be used at all.

Reacts with H₂O to produce urea

A) ornithine
B) citrulline
C) argininosuccinate
D) arginine

Question 42

Use the following to answer the questions below:
Following are reactants and the type of reaction they undergo. From the response list, select the product to which each reactant is converted. Responses may be used more than once or need not be used at all.


-Transamination involving pyruvate

A) alanine
B) aspartate
C) glutamate
D) ( $\alpha$ -ketoglutarate)

Question 43

Use the following to answer the questions below:
Following are reactants and the type of reaction they undergo. From the response list, select the product to which each reactant is converted. Responses may be used more than once or need not be used at all.


-Oxidative deamination involving glutamate

A) alanine
B) aspartate
C) glutamate
D) ( $\alpha$ -ketoglutarate)

Question 44

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) The source for both nitrogen atoms in a urea molecule is carbamoyl phosphate.
(2) In the second stage of amino acid degradation, ammonium ion is liberated from glutamate through oxidative deamination.
(3) Dietary protein intake and protein turnover are the body's only sources for providing amino acids for the amino acid pool.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 45

Use the following to answer the questions below:
For the degradation products found for a particular amino acid carbon skeleton, use the response list to characterize the amino acid in terms of ketogenicity and glucogenicity.

Both fumarate and oxaloacetate

A) ketogenic but not glucogenic
B) glucogenic but not ketogenic
C) both ketogenic and glucogenic
D) neither ketogenic nor glucogenic

Question 46

Use the following to answer the questions below:
For the degradation products found for a particular amino acid carbon skeleton, use the response list to characterize the amino acid in terms of ketogenicity and glucogenicity.

Pyruvate only

A) ketogenic but not glucogenic
B) glucogenic but not ketogenic
C) both ketogenic and glucogenic
D) neither ketogenic nor glucogenic

Question 47

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Stercobilin, a bile pigment, is the substance that gives fecal matter its brown color.
(2) Glycolysis and citric acid cycle intermediates are the starting materials for amino acid biosynthesis.
(3) The urea cycle participants arginine and citrulline are both nonstandard amino acids.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 48

Use the following to answer the questions below:
For the degradation products found for a particular amino acid carbon skeleton, use the response list to characterize the amino acid in terms of ketogenicity and glucogenicity.

Succinyl CoA only

A) ketogenic but not glucogenic
B) glucogenic but not ketogenic
C) both ketogenic and glucogenic
D) neither ketogenic nor glucogenic

Question 49

Use the following to answer the questions below:
For each of the urea cycle characterizations, select a correct response from the response list. Responses may be used more than once or need not be used at all.

Fumarate is a product of its "breakup"

A) ornithine
B) citrulline
C) argininosuccinate
D) arginine

Question 50

Use the following to answer the questions below:
For each of the urea cycle characterizations, select a correct response from the response list. Responses may be used more than once or need not be used at all.

Reacts with aspartate

A) ornithine
B) citrulline
C) argininosuccinate
D) arginine

Question 51

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) A reactant and a product in the first step of the urea cycle are, respectively, ornithine and citrulline.
(2) Degradation of heme begins with a ring-opening reaction in which carbon monoxide is produced.
(3) With a normal diet, only about 10 percent of our total calories come from protein.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 52

Use the following to answer the questions below:
For the degradation products found for a particular amino acid carbon skeleton, use the response list to characterize the amino acid in terms of ketogenicity and glucogenicity.

Acetyl CoA only

A) ketogenic but not glucogenic
B) glucogenic but not ketogenic
C) both ketogenic and glucogenic
D) neither ketogenic nor glucogenic

Question 53

Use the following to answer the questions below:
For each of the urea cycle characterizations, select a correct response from the response list. Responses may be used more than once or need not be used at all.

Reacts with carbamoyl phosphate

A) ornithine
B) citrulline
C) argininosuccinate
D) arginine

Question 54

Use the following to answer the questions below:
For each of the urea cycle characterizations, select a correct response from the response list. Responses may be used more than once or need not be used at all.

Is one of the standard amino acids

A) ornithine
B) citrulline
C) argininosuccinate
D) arginine

Question 55

Use the following to answer the questions below:
Following are reactants and the type of reaction they undergo. From the response list, select the product to which each reactant is converted. Responses may be used more than once or need not be used at all.


-Transamination involving glutamate

A) alanine
B) aspartate
C) glutamate
D) ( $\alpha$ -ketoglutarate)

Question 56

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) Each of the 20 standard amino acid carbon skeletons undergoes a different degradation process.
(2) The net effect of the urea cycle is the production of urea from ammonium ions and acetyl CoA.
(3) In transamination, the amino group of an amino acid is interchanged with the acid group of an alpha-keto acid.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 57

Use the following to answer the questions below:
In each of the following multiple-choice questions, characterize EACH of the three given statements as being TRUE or FALSE and then indicate the collective true-false status of the statements using the choices:
Statements: (1) The major organic and inorganic solutes in urine are, respectively, urea and chloride ion.
(2) Nitric oxide is an extremely reactive gaseous chemical messenger in cells that is produced from the reaction of oxygen with the amino acid arginine.
(3) The action of nitroglycerin, as a heart medication, is related to NO production.

A) All three statements are true.
B) Two of the three statements are true.
C) Only one of the statements is true.
D) None of the statements is true.

Question 58

Use the following to answer the questions below:
Following are reactants and the type of reaction they undergo. From the response list, select the product to which each reactant is converted. Responses may be used more than once or need not be used at all.


-Transamination involving oxaloacetate

A) alanine
B) aspartate
C) glutamate
D) ( $\alpha$ -ketoglutarate)

Question 59

Use the following to answer the questions below:
For the degradation products found for a particular amino acid carbon skeleton, use the response list to characterize the amino acid in terms of ketogenicity and glucogenicity.

Both acetyl CoA and acetoacetyl CoA

A) ketogenic but not glucogenic
B) glucogenic but not ketogenic
C) both ketogenic and glucogenic
D) neither ketogenic nor glucogenic

Question 60

Use the following to answer the questions below:
Following are reactants and the type of reaction they undergo. From the response list, select the product to which each reactant is converted. Responses may be used more than once or need not be used at all.


-Transamination involving $\alpha$ -ketoglutarate

A) alanine
B) aspartate
C) glutamate
D) ( $\alpha$ -ketoglutarate)

Question 61

Use the following to answer the questions below:
For each of the heme degradation characterizations, select a correct degradation product from the response list. Responses may be used more than once or need not be used at all.

CO is produced at the same time as this substance.

A) bilirubin
B) biliverdin
C) stercobilin
D) urobilin

Question 62

Use the following to answer the questions below:
For each of the heme degradation characterizations, select a correct degradation product from the response list. Responses may be used more than once or need not be used at all.

Buildup of this substance in the blood produces jaundice.

A)translation phase of protein synthesis
B)transcription phase of protein synthesis
C)replication of DNA
D)post-transcription phase of protein synthesis

Question 63

Use the following to answer the questions below:
For each of the heme degradation characterizations, select a correct degradation product from the response list. Responses may be used more than once or need not be used at all.

Substance that gives urine its characteristic color

A)translation phase of protein synthesis
B)transcription phase of protein synthesis
C)replication of DNA
D)post-transcription phase of protein synthesis

Question 64

Use the following to answer the questions below:
In each of the following reactant-product combinations associated with the production of urea, contrast the nitrogen content of the two compounds using the response list. Responses may be used more than once or need not be used at all.

Arginine-ornithine

A) Nitrogen content remains the same.
B) Nitrogen content increases by one atom.
C) Nitrogen content increases by two atoms.
D) Nitrogen content decreases by two atoms.

Question 65

Use the following to answer the questions below:
For each of the heme degradation characterizations, select a correct degradation product from the response list. Responses may be used more than once or need not be used at all.

Molecular O₂ is required as a reactant to produce this substance.

A)translation phase of protein synthesis
B)transcription phase of protein synthesis
C)replication of DNA
D)post-transcription phase of protein synthesis

Question 66

Use the following to answer the questions below:
In each of the following reactant-product combinations associated with the production of urea, contrast the nitrogen content of the two compounds using the response list. Responses may be used more than once or need not be used at all.

Carbamoyl phosphate-citrulline

A) Nitrogen content remains the same.
B) Nitrogen content increases by one atom.
C) Nitrogen content increases by two atoms.
D) Nitrogen content decreases by two atoms.

Question 67

Use the following to answer the questions below:
In each of the following reactant-product combinations associated with the production of urea, contrast the nitrogen content of the two compounds using the response list. Responses may be used more than once or need not be used at all.

Arginine-urea

A) Nitrogen content remains the same.
B) Nitrogen content increases by one atom.
C) Nitrogen content increases by two atoms.
D) Nitrogen content decreases by two atoms.

Question 68

Use the following to answer the questions below:
In each of the following reactant-product combinations associated with the production of urea, contrast the nitrogen content of the two compounds using the response list. Responses may be used more than once or need not be used at all.

Ammonium ion-carbamoyl phosphate

A) Nitrogen content remains the same.
B) Nitrogen content increases by one atom.
C) Nitrogen content increases by two atoms.
D) Nitrogen content decreases by two atoms.

Question 69

Use the following to answer the questions below:
For each of the heme degradation characterizations, select a correct degradation product from the response list. Responses may be used more than once or need not be used at all.

Substance that gives feces its characteristic color

A)translation phase of protein synthesis
B)transcription phase of protein synthesis
C)replication of DNA
D)post-transcription phase of protein synthesis

Question 70

Use the following to answer the questions below:
In each of the following reactant-product combinations associated with the production of urea, contrast the nitrogen content of the two compounds using the response list. Responses may be used more than once or need not be used at all.

Citrulline-argininosuccinate

A) Nitrogen content remains the same.
B) Nitrogen content increases by one atom.
C) Nitrogen content increases by two atoms.
D) Nitrogen content decreases by two atoms.