Bachelor of Pharmacy (B.Pharm.) Biochemistry Flashcards

Which coenzyme is required for the oxidative decarboxylation of pyruvate to acetyl-CoA?

Answer: Thiamine pyrophosphate

Thiamine pyrophosphate (TPP) is the essential coenzyme for the pyruvate dehydrogenase complex that catalyzes decarboxylation of pyruvate.

In the urea cycle, which amino acid donates both nitrogen atoms that appear in urea?

Answer: Aspartate and ammonia

One nitrogen in urea comes from free ammonia (via carbamoyl phosphate) and the second comes from aspartate.

Which enzyme is rate-limiting in cholesterol biosynthesis?

Answer: HMG-CoA reductase

HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate and is the committed, rate-limiting step in cholesterol synthesis.

The Cori cycle transfers energy from the liver to working muscles in what chemical form?

Answer: Glucose

The liver converts lactate (from muscles) back to glucose via gluconeogenesis and releases it into the blood for muscle use.

Which type of RNA carries amino acids to the ribosome during translation?

Answer: tRNA

Transfer RNA (tRNA) carries specific amino acids to the ribosome and matches them to codons on mRNA via its anticodon loop.

Competitive inhibition of an enzyme increases the apparent Km but leaves Vmax unchanged. Which statement best explains this?

Answer: Excess substrate can displace the inhibitor from the active site

Competitive inhibitors bind reversibly to the active site; high substrate concentrations outcompete the inhibitor, restoring full Vmax.

Which vitamin deficiency causes beriberi and is directly linked to impaired pyruvate dehydrogenase activity?

Answer: Vitamin B1 (thiamine)

Thiamine (B1) is a precursor of TPP, the required cofactor for pyruvate dehydrogenase; its deficiency impairs aerobic glucose metabolism causing beriberi.