PCAT Biochemistry 2

Question 1

Which enzyme catalyzes the committed step of glycolysis?

Accepted Answer

Phosphofructokinase-1

Answer

Phosphofructokinase-1 (PFK-1) catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate, which is the committed and rate-limiting step of glycolysis.

Question 2

What is the primary function of ubiquinone (CoQ) in the electron transport chain?

Accepted Answer

Transfers electrons from complexes I and II to complex III

Answer

Ubiquinone (CoQ) is a mobile electron carrier that collects electrons from NADH (via Complex I) and FADH2 (via Complex II) and transfers them to Complex III.

Question 3

Which amino acid serves as the direct precursor for dopamine biosynthesis?

Accepted Answer

Tyrosine

Answer

Tyrosine is hydroxylated to L-DOPA by tyrosine hydroxylase, then decarboxylated to dopamine by DOPA decarboxylase.

Question 4

A patient with a deficiency in glucose-6-phosphatase would be unable to perform which process?

Accepted Answer

Glycogenolysis releasing free glucose to blood

Answer

Glucose-6-phosphatase, found mainly in the liver, removes the phosphate from glucose-6-phosphate so free glucose can be exported into the bloodstream; its deficiency causes Von Gierke disease.

Question 5

In the urea cycle, which nitrogen-containing compound directly donates one of the two nitrogen atoms incorporated into urea?

Accepted Answer

Aspartate

Answer

Aspartate donates its amino group to argininosuccinate, contributing the second nitrogen atom of urea; ammonia provides the first nitrogen via carbamoyl phosphate.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Biochemistry 2