NBME Comprehensive Basic Science 2

Question 1

A patient with chronic alcoholism presents with peripheral neuropathy and Wernicke's encephalopathy. Which enzyme requires the deficient cofactor?

Accepted Answer

Pyruvate dehydrogenase

Answer

Lactate dehydrogenase

Answer

Glucose-6-phosphate dehydrogenase

Answer

Glutamate dehydrogenase

Question 2

A cell exposed to hypotonic solution swells and lyses. Which membrane transport mechanism is responsible for the initial water influx?

Accepted Answer

Facilitated diffusion via aquaporins

Answer

Active transport via Na+/K+ ATPase

Answer

Vesicle-mediated endocytosis

Answer

Carrier-mediated secondary active transport

Question 3

During DNA replication, which enzyme removes RNA primers and fills the resulting gaps with DNA?

Accepted Answer

DNA polymerase I

Answer

DNA polymerase III

Answer

DNA ligase

Answer

Primase

Question 4

A researcher blocks the proteasome in a cell. Which of the following processes is most directly impaired?

Accepted Answer

Degradation of ubiquitin-tagged misfolded proteins

Answer

Lysosomal autophagy of organelles

Answer

Translation of mRNA by ribosomes

Answer

Post-translational glycosylation in the Golgi

Question 5

A mutation eliminates the Shine-Dalgarno sequence in a bacterial mRNA. What is the most likely result?

Accepted Answer

Reduced translation initiation

Answer

Premature transcription termination

Answer

Inability to splice introns

Answer

Failure of mRNA capping

Question 6

Which glycolytic intermediate directly donates phosphate to ADP to produce ATP via substrate-level phosphorylation?

Accepted Answer

Phosphoenolpyruvate

Answer

Fructose-1,6-bisphosphate

Answer

Glucose-6-phosphate

Answer

3-Phosphoglycerate

Question 7

A patient has a defect in the enzyme that hydroxylates proline residues in collagen. Which cofactor is most likely deficient?

Accepted Answer

Ascorbic acid (Vitamin C)

Answer

Pyridoxal phosphate (B6)

Answer

Cobalamin (B12)

Answer

Riboflavin (B2)