Q: Which of the following is the general form of a transamination reaction?

$$ \mathrm{Amino\ $$acid_1$$ + \alpha\text{-}ketoglutarate \rightarrow \alpha\text{-}keto\ $$acid_1$$ + glutamate} $$

Question 1

Which of the following best describes the overall reaction for biological nitrogen fixation catalyzed by nitrogenase?

Accepted Answer

$$ \mathrm{N_2$ + 8H^+ + 8e^- + 16ATP \rightarrow 2NH_3 + H_2$ + 16ADP + 16P_i} $$

Question 2

Which of the following is NOT a primary way ammonia is assimilated into biomolecules in humans?

Accepted Answer

Direct incorporation into urea without any intermediate

Question 3

Which of the following statements about protein degradation in eukaryotic cells is CORRECT?

Accepted Answer

Proteins are primarily degraded in the cytosol by the proteasome after being tagged with ubiquitin.

Question 4

Which coenzyme is most commonly involved in transamination reactions?

Accepted Answer

Pyridoxal phosphate (PLP)

Question 5

Which of the following is the general form of a transamination reaction?

Accepted Answer

$$ \mathrm{Amino\ $$acid_1$$ + \alpha	ext{-}ketoglutarate ightarrow \alpha	ext{-}keto\ $$acid_1$$ + glutamate} $$

Question 6

In what forms is ammonia primarily transported from peripheral tissues to the liver?

Accepted Answer

As glutamine and alanine

Question 7

Which of the following correctly describes the net reaction of the urea cycle?

Accepted Answer

$$ \mathrm{2NH_3 + CO_2$ + 3ATP + H_2O \rightarrow urea + 2ADP + 4P_i + AMP + 2H^+} $$

Question 8

Which amino acid is both glucogenic and ketogenic?

Accepted Answer

Isoleucine

Question 9

Which metabolic intermediate is a precursor for the synthesis of serine?

Accepted Answer

3-phosphoglycerate

Question 10

S-adenosylmethionine (AdoMet) is primarily used in cells for which type of reaction?

Accepted Answer

Methyl group transfer

Question 11

Which statement about purine biosynthesis is CORRECT?

Accepted Answer

The purine base is built stepwise while attached to ribose-5-phosphate.

Question 12

A patient with Lesch-Nyhan syndrome has a deficiency in which enzyme, and what is a consequence of this deficiency?

Accepted Answer

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT); increased uric acid production

Question 13

Which of the following is TRUE regarding pyrimidine biosynthesis?

Accepted Answer

The pyrimidine ring is synthesized first, then attached to ribose-5-phosphate.

Question 14

Which enzyme is responsible for converting ribonucleotides to deoxyribonucleotides, and what is unique about its regulation?

Accepted Answer

Ribonucleotide reductase (RNR); it is regulated by both allosteric effectors and substrate specificity

Question 15

5-Fluorouracil (FUra) is used as a chemotherapeutic agent because it inhibits which process?

Accepted Answer

Synthesis of thymine nucleotides by inhibiting thymidylate synthase

Question 16

Which of the following best describes the mechanism of G protein-coupled receptor (GPCR) activation?

Accepted Answer

Ligand binding induces a conformational change, activating a heterotrimeric G protein by exchanging GDP for GTP on the α subunit.

Question 17

Which statement about receptor tyrosine kinases (RTKs) is CORRECT?

Accepted Answer

Ligand binding induces dimerization and autophosphorylation of the receptor.

Question 18

Steroid and thyroid hormone receptors are unique among hormone receptors because they:

Accepted Answer

Are intracellular and directly bind to DNA to regulate gene expression.

Question 19

Which of the following best describes the difference between oncogenes and tumor suppressor genes?

Accepted Answer

Oncogenes promote cell division when mutated, while tumor suppressor genes prevent cell division and require both alleles to be inactivated for cancer to develop.

Question 20

Which of the following statements about cholinergic signaling is CORRECT?

Accepted Answer

Acetylcholine acts as a neurotransmitter at both nicotinic and muscarinic receptors.

Amino Acid and Nitrogen Metabolism, Nucleotide Metabolism, and Signal Transduction: Study Guide for CHEM 4510 Exam III

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