Deck 24: The Biosynthesis of Amino Acids

Question 1

What process converts N₂ to NH₃?

A) urea cycle
B) glutamine hydrolysis
C) denitrification
D) nitrogen fixation
E) None of the answers is correct.

Answer 1

D

Question 2

Homocysteine is an intermediate in the synthesis of cysteine and _______________.

Answer 2

methionine

Question 3

The enzyme _______________ contains a selenium analogue of cysteine.

Answer 3

glutathione peroxidase

Question 4

Methyl,methylene,and _______________ units can be carried by tetrahydrofolate.

Question 5

What common biochemical strategy allows ammonia to be generated for use within the same enzyme?

A) ammonia fixation
B) glutamine hydrolysis
C) ammonia activation
D) glutamate hydrolysis
E) None of the answers is correct.

Question 6

Glutamate is the carbon skeleton precursor for the amino acids glutamine,proline,and ______________.

Question 7

Glutamine synthetase adds NH₃ to _______________ to make glutamine.

Question 8

The protein ________________stores iron,whereas the protein transferrin transports it.

Question 9

Which of the following is a vasodilator that is derived from histidine?

A) epinephrine
B) norepinephrine
C) histamine
D) adenosine
E) prostacyclin

Question 10

Glycine condenses with succinyl CoA in the first step of ____________ synthesis.

A) thiamine
B) histamine
C) glutathione
D) porphyrin
E) folate

Question 11

Which of the following is a tripeptide that functions as an antioxidant?

A) glutathione
B) aspartame
C) oxytocin
D) thyrotropin-releasing hormone
E) None of the answers is correct.

Question 12

At least _____________ ATP molecules are hydrolyzed for each N₂ reduced.

Question 13

Which of the following is a versatile carrier of several different one-carbon units?

A) pyridoxal phosphate
B) biotin
C) tetrahydrofolate
D) coenzyme A
E) None of the answers is correct.

Question 14

The enzyme _______________ is regulated by cumulative feedback inhibition.

Question 15

Which of the following is the original nitrogen source for the nitrogen found in amino acids?

A) atmospheric nitrogen (N₂)
B) tetrahydrofolate
C) glutamine
D) ammonia (NH₃)
E) urea

Question 16

The α-amino group found in most amino acids comes from _______________by a transamination reaction.

Question 17

What molecule is an activated form of ribose phosphate and a precursor for histidine?

A) ribose triphosphate
B) PRPP (5-phosphoribosyl-1-pyrophosphate)
C) ATP
D) cyclic AMP
E) None of the answers is correct.

Question 18

What molecule is the precursor for the biosynthesis of serine,cysteine,and glycine?

A) pyruvate
B) oxaloacetate
C) $\alpha$ -ketoglutarate
D) glyceraldehyde-3-phosphate
E) 3-phosphoglycerate

Question 19

What vitamin is the precursor for methylcobalamin?

A) B₂
B) B₆
C) B₇
D) B₉
E) B₁₂

Question 20

The _______________ reaction establishes the stereochemistry at the α-carbon atom in amino acids.

Question 21

How may have feedback inhibition processes evolved?

A) duplication of genes encoding catalytic domains
B) evolution of homologous subunits in the enzyme catalyzing the committed step
C) linking specific regulatory domains to catalytic domains
D) linking of multiple regulatory domains to one another
E) All of the answers are correct.

Question 22

Chorismate is a precursor to the amino acids

A) tryptophan, tyrosine, and phenylalanine.
B) serine, glycine and cysteine.
C) isoleucine, leucine and valine.
D) methionine, threonine, and lysine.
E) None of the answers is correct.

Question 23

What amino acid is added to indole in the biosynthesis of tryptophan?

A) glutamine
B) serine
C) tyrosine
D) alanine
E) None of the answers is correct.

Question 24

Describe the structure and function of the FeMo cofactor.

Question 25

The ATP-binding region of the nitrogen-fixating reductase is a(n)___________ domain.

A) iron-sulfur
B) electron-binding
C) P-loop NTPase family
D) molybdenum-binding
E) All the answers are correct.

Question 26

S-Adenosylmethionine carries _______________groups.

A) methyl
B) CO₂
C) ammonia
D) formyl
E) None of the answers is correct.

Question 27

Organisms capable of carrying out reduction of atmospheric nitrogen include

A) some bacteria and archaea.
B) higher eukaryotic organisms, such as mammals.
C) all plants.
D) fungi, including yeasts and molds.
E) None of the answers is correct.

Question 28

Essential amino acids (for humans)differ from nonessential amino acids in that

A) nonessential amino acids are synthesized in simple reaction pathways compared to complex pathways for most essential amino acids.
B) essential amino acids are generally synthesized directly from citric acid cycle intermediates, but not nonessential amino acids.
C) microorganisms and animals cannot synthesize essential amino acids but plants can.
D) animals cannot synthesize essential amino acids because they have lost the ability to carry out transamination reactions.
E) All of the answers are correct.

Question 29

Describe the process and proteins involved in nitrogen fixation.

Question 30

Although nitrogen is abundant in the form of atmospheric nitrogen,it presents a fundamental problem for use in biological systems.What is the problem,and how is it resolved?

Question 31

The peptide glutathione

A) has a glutamate residue linked to glycine through its α-amine.
B) plays a role in the synthesis of the purine guanine.
C) is required to catalyze the transamination of glutamate from α-ketoglutarate.
D) is used to detoxify cells by reacting with organic peroxides.
E) functions as a one-carbon transfer molecule.

Question 32

The carbon skeletons used to synthesize amino acids are intermediates found in

A) glycolysis.
B) glycogen metabolism.
C) citric acid cycle.
D) All the answers are correct.
E) glycolysis and citric acid cycle

Question 33

Tryptophan is a precursor for the neurotransmitter(s)

A) serotonin.
B) norepinephrine.
C) adenine.
D) $\gamma$ -aminobutyric acid.
E) None of the answers is correct.

Question 34

This amino acid,in high levels,is correlated with the damage of cells lining the blood vessels.

A) serine
B) cysteine
C) S-adenosylmethionine
D) citrulline
E) homocysteine

Question 35

An example of a reaction controlled by enzyme multiplicity is

A) phosphorylation of asparagine by aspartokinases.
B) phosphorylation of aspartate by aspartokinases.
C) phosphorylation of glutamine by glutamine synthetase.
D) all of the above.
E) None of the answers is correct.

Question 36

Amino acid synthesis is primarily regulated by

A) turnover.
B) diet.
C) urea excretion.
D) allosteric enzyme regulation.
E) All the answers are correct.

Question 37

What is the activated methyl cycle?

Question 38

In comparing transaminase enzymes,certain amino acids have been conserved.What are these amino acids,and how are they important in determining the proper chirality of the new amino acid?

Question 39

Nitric oxide

A) is a short-lived signal molecule.
B) is generated by the oxidation of lysine.
C) requires NADP⁺ and O₂ for synthesis.
D) is metabolized be reaction with ornithine.
E) All of the answers are correct.

Question 40

Tyrosine is a precursor to the molecule(s)

A) melanin.
B) epinephrine.
C) serotonin.
D) melanin and epinephrine
E) melanin and serotonin.

Question 41

What caused the "madness" of King George III?

Question 42

What is the advantage of the enzymatic cascade for the regulation of glutamine synthetase activity?

Question 43

What unusual (and not recommended)experiments were carried out by Shemin and colleagues?

Question 44

What is enzyme multiplicity?

Question 45

How does the herbicide glyphosate work?

Question 46

What is catalytic substrate channeling?

Question 47

Describe the regulation of the enzyme threonine deaminase.

Question 48

What do S-adenosylmethionine and fruit ripening have in common?