Question 1

Which of the following best describes a transamination reaction in amino acid metabolism?

Accepted Answer

A reaction where an NH3 group is transferred from one molecule to another.

Question 2

Which cofactor is required by aminotransferases to catalyze transamination reactions?

Accepted Answer

PLP (Pyridoxal phosphate)

Question 3

If the equilibrium constant $$K_{eq}$$ for a transamination reaction is near 1, what does this indicate about the reaction?

Accepted Answer

The concentrations of products and reactants are approximately equal.

Question 4

SGOT (Serum glutamate-oxaloacetate transaminase) catalyzes which of the following reactions?

Accepted Answer

Glutamate + oxaloacetate $$\xrightarrow{SGOT}$$ $$\alpha-$$ketoglutarate + aspartate

Question 5

In the glucose-alanine cycle, what is the primary purpose of transporting alanine from muscle to liver?

Accepted Answer

To transfer nitrogen from skeletal muscle to the liver for ammonia detoxification.

Question 6

Which of the following correctly lists the reactants and enzyme for the first step of the urea cycle?

Accepted Answer

NH4+, HCO3-, 2 ATP, and carbamoyl phosphate synthetase (CPSI)

Question 7

Which amino acids are exclusively ketogenic?

Accepted Answer

Leucine and Lysine

Question 8

Which of the following amino acids is degraded to oxaloacetate?

Accepted Answer

Asparagine

Question 9

Asparaginase is used in the treatment of lymphoblastic leukemia because:

Accepted Answer

It disables the conversion of asparagine to aspartate, depriving malignant cells of asparagine.

Question 10

Which of the following statements about essential amino acids is correct?

Accepted Answer

Essential amino acids must be obtained from the diet because they cannot be synthesized in sufficient quantities.

Question 11

Which amino acids are derived from intermediates of glycolysis?

Accepted Answer

Serine, glycine, cysteine

Question 12

What are the three chemical steps for the synthesis of serine from 3-phosphoglycerate?

Accepted Answer

Oxidation with NAD+, PLP-dependent transamination, dephosphorylation with water

Question 13

Which of the following is a common metabolic intermediate produced from the degradation of amino acids?

Accepted Answer

Acetoacetate

Question 14

Which amino acid is degraded to $$\alpha-$$ketoglutarate after conversion from glutamine?

Accepted Answer

Glutamate

Question 15

The degradation of branched chain amino acids shares a chemical strategy with the citric acid cycle and fatty acid oxidation because:

Accepted Answer

They all involve the removal of two carbons at a time after the first transamination reaction.

Question 16

Which amino acids are both glucogenic and ketogenic?

Accepted Answer

Tyrosine, Phenylalanine, Threonine, Isoleucine, Tryptophan

Question 17

Which pathway provides the intermediates for the biosynthesis of histidine, tryptophan, phenylalanine, and tyrosine?

Accepted Answer

Pentose phosphate pathway

Question 18

Which of the following best explains why serine and glycine are central to many other essential metabolic processes?

Accepted Answer

They can be interconverted and serve as precursors for a variety of important biomolecules.

Question 19

Which enzyme catalyzes the conversion of carbamoyl phosphate to citrulline in the urea cycle?

Accepted Answer

Ornithine transcarbamoylase

Question 20

A patient with a deficiency in ornithine transcarbamoylase would most likely accumulate which urea cycle intermediate?

Accepted Answer

Carbamoyl phosphate

Amino Acid and Nitrogen Metabolism: Step-by-Step Study Guidance

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