Deck 21: Metabolism of Nitogenous Compounds II: Amino Acids, Porphyrins, and Neurotransmitters

Question 1

Which of the following molecules uses chorismate as a precursor?

A)p-aminobenzoic acid
B)coenzyme Q
C)phenylalanine
D)tryptophan
E)all of the above

Answer 1

E

Question 2

The regeneration of methionine from homocysteine relies upon the conversion of _________ to __________ as a source of carbon.

A)alanine; pyruvate
B)phenylalanine; tyrosine
C)cystathionine; cysteine
D)proline; glutamate
E)serine; glycine

Answer 2

E

Question 3

The importance of regenerating methionine can be seen in the multiple methionine regeneration pathways found in the liver, such as the pathway that uses betaine as a methyl group donor. What glycerophospholipid component is the precursor for betaine?

A)ethanolamine
B)glycerol
C)choline
D)serine
E)none of the above

Answer 3

C

Question 4

The catabolism of leucine to acetyl-CoA produces three molecules of acetyl-CoA, one NADH, and one FADH₂,while consuming two ATP. What is the net ATP production from the complete oxidation of the leucine carbon skeleton?

A)30
B)32
C)34
D)36
E)none of the above

Question 5

In the pathway for conversion of phenylalanine to fumarate and acetoacetate, there are two well-known enzyme defects that cause inheritable metabolic diseases. What are the names of these two diseases?

A)homocysteinuria and nonketotic hyperglycinemia
B)phenylketonuria and maple syrup urine disease
C)alkaptonuria and nonketotic hyperglycinemia
D)alkaptonuria and phenylketonuria
E)maple syrup urine disease and homocysteinuria

Question 6

Of the following molecules derived from amino acids, which is used to transport amino acids across the cell membrane?

A)glutathione
B) $\gamma$ -aminobutyric acid
C)S-adenosylmethionine
D)nitric oxide
E)thyroxine

Question 7

Glyphosate, the active molecule in the herbicide Roundup, is an inhibitor of the enzyme 5-enolpuruvylshikimate-3-phosphate synthase in the chorismate synthesis pathway. Which of the following amino acids would not be produced in a plant treated with Roundup?

A)glycine
B)serine
C)tyrosine
D)valine
E)proline

Question 8

Which pair of amino acids can be degraded to oxaloacetate and $\alpha$ -ketoglutarate, respectively?

A)aspartate, alanine
B)asparagine, histidine
C)histidine, serine
D)proline, arginine
E)threonine, glutamine

Question 9

Which of the following is a role of spermine and spermidine, the polyamines derived from glutamate?

A)stabilization of tRNA duplex structure
B)neutralization of DNA negative charge
C)stabilization of double stranded DNA
D)stabilization of bacterial membranes
E)all of the above

Question 10

Which amino acids are transaminated by the branched-chain amino acid aminotransferase?

A)valine, isoleucine and leucine
B)proline, valine and alanine
C)leucine, isoleucine and phenylalanine
D)leucine, isoleucine and proline
E)lysine, valine and leucine

Question 11

In animals, all nitrogen and carbon of heme groups comes from the reaction of the amino acid ________ and _________.

A)glutamate; malonyl-CoA
B)aspartate; acetyl-CoA
C)asparagine; propionyl-CoA
D)glycine; succinyl-CoA
E)alanine; methylmalonyl-CoA

Question 12

Threonine is converted into acetyl-CoA and pyruvate while proline is converted into $\alpha$ -ketoglutarate. Classify each of these amino acids.

A)threonine is ketogenic, proline is ketogenic
B)threonine is ketogenic and glucogenic, proline is ketogenic
C)threonine is ketogenic, proline is glucogenic
D)threonine is ketogenic and glucogenic, proline is glucogenic
E)none of the above

Question 13

One route for tryptophan degradation leads to the coenzyme _____________.

A)pyridoxal phosphate
B)FAD
C)NAD⁺
D)tetrahydrobiopterin
E)none of the above

Question 14

In bacteria, the biosynthetic routes for proline and arginine diverge when glutamate is N-acetylated for arginine synthesis. Which of the following explains why acetylation is required for arginine synthesis but not proline synthesis?

A)acetylation alters the pK_a of the amine group
B)acetylation prevents reduction of the amine group in N-acetylglutamate- $\delta$ -semialdehyde
C)acetylation activates the amine group for synthesis of the guanidine group of arginine
D)acetylation prevents the cyclization of N-acetylglutamate- $\delta$ -semialdehyde
E)none of the above

Question 15

Bilirubin is conjugated with _________ to increase its solubility for excretion.

A)phospholipids
B)glycine
C)glucuronic acid
D)taurine
E)all of the above

Question 16

Which of the following molecules derived from tyrosine is correctly defined?

A)dopamine: thyroid hormone
B)dopaquinone: precursor for melanins
C)thyroxine: catecholamine
D)norepinephrine: thyroid hormone
E)all of the above

Question 17

The conversion of tryptophan to 5-hydroxytryptophan in the serotonin synthesis pathway is analogous to the conversion of _________ to _________.

A)glycine; serine
B)phenylalanine; tyrosine
C)tyrosine to thyroxine
D)dopa to dopaquinone
E)all of the above

Question 18

Which of the following amino acids is derived from a glycolytic intermediate?

A)aspartate
B)threonine
C)proline
D)arginine
E)serine

Question 19

Which of the following explains the unique mechanism by which $\delta$ -aminolevulinic acid is synthesized in most bacteria, archaea and plants?

A)glutamic acid is attached to its tRNA and then reduced to glutamate-1-semialdehyde
B)glutamic acid undergoes reduction and cyclization to $\Delta$ ¹-pyrroline-5-carboxylate
C)glutamic acid undergoes carboxylation to $\gamma$ -carboxyglutamic acid
D)glutamic acid condenses with itself via the $\sigma$ -carboxyl and amine group
E)none of the above

Question 20

The route by which methionine is degraded provides for the synthesis of which amino acid?

A)serine
B)threonine
C)valine
D)isoleucine
E)cysteine

Question 21

Tryptophan is converted to serotonin, also known as 5-hydroxytryptamine. Show the intermediate and the product in the following synthetic pathway.

Question 22

Provide the two missing items in the scheme that shows the metabolism of threonine to glycine.

Question 23

Give the products of the following reaction in the $\gamma$ -glutamyl cycle. One product is an amino acid, the other, 5-oxoproline.

Question 24

The Ames test is used to measure the mutagenicity of molecules by introducing a potential mutagen to a culture of bacteria that cannot synthesize histidine. Which of the following explains the results if the bacteria are able to grow in a medium that lacks histidine?

A)all proteins expressed by the bacteria have mutated to not require histidine
B)defective histidine synthesis genes are mutated to forms that allow for histidine synthesis
C)the mutagen causes the bacteria to use some other molecule in place of histidine
D)the bacteria can convert the potential mutagen into histidine
E)none of the above

Question 25

Which amino acid utilizes nitrogen and carbon from adenine in the synthesis of its R-group?

A)histidine
B)arginine
C)lysine
D)asparagine
E)all of the above