Unit 3: Amino Acid Questions

B

Alanine can be synthesized by transamination directly from which of the following metabolites? A lactate B pyruvate C glutarate D α-ketoglutarate E 3-phosphoglycerate

D

Which of the following is true about the urea cycle: A All the reactions occur in the mitochondrion. B Urea is made in all cells. C Production of urea from amino acids requires a net use of 4 high-energy bonds. D The urea cycle is also used to synthesize arginine. E Transaminases are necessary for the continued synthesis of urea.

D

Which of the following is true about the urea cycle? A All the reactions occur in the mitochondria. B Urea is made in all cells. C Production of urea from amino acids only occurs in muscle, after exercise. D The urea cycle is also used to synthesize arginine. E Transaminases are necessary for the continued synthesis of urea.

D

An amino acid is considered to be ketogenic if one of the products of the breakdown of the amino acid is: A pyruvate B oxaloacetate C carbon dioxide D acetoacetate E malate

A

In amino acid degradation, the amino group of most amino acids gets transferred to: A α-ketoglutarate to form glutamate. B oxaloacetate to form aspartate. C α-ketoisocaproate to form leucine. D pyruvate to form alanine. E glutamate to form glutamine.

B

In starvation the *major* metabolic role of amino acids is to provide? A a source of NH4+ B a carbon source for synthesis of glucose C a source of acetyl-CoA D a precursor for adrenaline and epinephrine E building blocks for synthesis of proteins

B

In the urea cycle . . . A. ornithine is consumed. B. arginine is also synthesized. C. carbamoyl-phosphate must be formed from NH4+. D. the nitrogens come from glutamic acid and asparagines. E. the nitrogens come from glutamic acid and aspartic acid.

B

In the urea cycle, the two nitrogens in urea come from? A glutamic acid B aspartic acid and glutamine C glutamic acid and asparagine D ammonium E glutamic acid and aspartic acid

D

NADH + NH4+ + CO2 + N5,N10-Methylene-THF ↔ glycine + dihydrofolate + NAD+ (also attached) The reaction for the enzyme glycine synthase is shown. In the test tube this enzyme can synthesize glycine from NH4+, CO2, NAD+ and methylene-THF. It cannot synthesize glycine in the liver because: A. The temperature is 37 degrees C. B. The concentration of NAD+ is too low. C. There is not enough methylene THF. D. The concentration of NH4+ is too low E. ATP inhibits the reaction.

E

The pathway for the breakdown of leucine is shown. The following statement is true about the breakdown of leucine: A Leucine is used in glycolysis. B Conversion of leucine to Acetyl-CoA occurs in the nucleus. C Leucine is glucogenic. D *No* transaminase is required for any reaction in the pathway. E. Leucine is ketogenic.

E

The pathway for the catabolism of isoleucine is shown. Which of the following statements about isoleucine is true? A isoleucine is only ketogenic B conversion of isoleucine to acetyl-CoA does not require a transaminase C isoleucine is only glucogenic D tetrahydrofolate is a cofactor for one of the reactions with isoleucine E. isoleucine is glucogenic and ketogenic

E

The pathway for the catabolism of leucine is shown below. Which of the following statements about leucine is true? A Leucine is only glucogenic B Conversion of leucine to acetyl-CoA does not require a transaminase C Leucine is glucogenic and ketogenic. D Tetrahydrofolate is a cofactor for one of the reactions with leucine catabolism. E. Leucine is ketogenic

C

The pathway of tryptophan degradation is shown. Which of the following statements is true about tryptophan? A Tryptophan catabolism requires vitamin B2. B Trytophan is only ketogenic. C Tryptophan is both ketogenic and glucogenic. D Tryptophan is only glucogenic. E Tryptophan is a non-essential amino acid.

E

The reaction for the enzyme glutamate dehydrogenase is shown: In the test tube this reaction favors the synthesis of glutamate. The enzyme can synthesize α-ketoglutarate in the liver because . . . ? A The temperature is 37 degrees C. B The concentration of NAD+ is too low. C There is not enough methylene THF. D ATP inhibits the reaction. E The concentration of NH4+ is maintained very low.

D

The reaction for the enzyme glycine synthase is shown. In the test tube this enzyme can synthesize glycine from NH4+, CO2, NAD+ and methylene-THF. It cannot synthesize glycine in the liver because: A. The temperature is 37 °C. B. The concentration of NAD+ is too low. C. There is not enough methylene THF. D. The concentration of NH4+ is too low. E. ATP inhibits the reaction.

C

The synthesis of citrulline . . . A takes place in the cytoplasm. B occurs in all cells. C takes place in the mitochondrion. D is required for synthesis of cysteine. E occurs from proline.

A

When glutamate containing N-15 isotope in the alpha amino group is administered to a human, the N-15 will be found in: A the alpha amino group of all non-essential amino acids B the amino group in the side chains of all essential amino acids C hippurate D S-adenosyl methionine E the tetrahydrofolate one carbon pool

B

When the body needs more glucose, pyruvate produced in muscle from protein catabolism can be transported to the liver by first being converted to an amino acid. This amino acid is A aspartate B alanine C α-ketoglutarate D glutamate E glutamine

D

Which of the following amino acids can most easily be converted to tyrosine in the human body? A Glycine B Arginine C Methionine D Phenylalanine E Tryptophan

A

Which of the following is true about people with phenylketonuria? A They cannot hydroxylate phenylalanine to make tyrosine B They have a defect in the metabolism of phenyltyrosine (the α-keto acid of phenylalanine) C Tyrosine is no longer an essential amino acid D They can now convert phenylalanine to tryptophan E They have to restrict their use of the amino acid tyrosine.

A

Which of the following reactions in mammals use ammonium (NH4+) as a substrate? A. synthesis of glutamine from glutamic acid B. synthesis of serine C. synthesis of glycine D. synthesis of α-ketoglutarate from glutamic acid E. synthesis of asparagine from aspartic acid

C

Which of the following statements is NOT true about transamination reactions? A Vitamin B6 is necessary for the reaction. B Pyridoxal phosphate is a coenzyme involved in the reaction. C They result in the net synthesis of an amino acid. D A transamination reaction is required in the synthesis of serine E They are part of the pathway for catabolism of most amino acids

A

Which of the following statements is true about transamination reactions? A Vitamin B6 is necessary for the reaction. B Pyridoxal phosphate is not required in the reaction. C They change the quantity of amino acids. D A transamination reaction is required in the synthesis of pyruvate from glucose. E They occur in the mitochondrion.

D

Which of the following statements is true about amino acid metabolism in mammals? A Serine can be synthesized completely from other amino acids. B Phenylalanine is not an essential amino acid for people with phenylketonuria. C Amino acids are the primary source of acetyl CoA. D Vitamin B6 is the major coenzyme in reactions involving transamination of keto acids. E Ammonium is removed by incorporation into the amide nitrogen of glucose.

A

Which of the following statements is true about transamination reactions: A Vitamin B6 is necessary for the reaction. B Pyridoxal phosphate is not required in the reaction. C They change the quantity of amino acids. D A transamination reaction is required in the synthesis of pyruvate from glucose. E They occur mostly in the mitochondrion.