PCAT Biochemistry 4

Question 1

During beta-oxidation of a 16-carbon saturated fatty acid (palmitate), how many acetyl-CoA molecules are produced?

Accepted Answer

8

Answer

A 16-carbon fatty acid undergoes 7 rounds of beta-oxidation, yielding 8 acetyl-CoA molecules, 7 FADH2, and 7 NADH.

Question 2

Which of the following best describes the role of calmodulin in cellular signaling?

Accepted Answer

It is a calcium-binding protein that activates target enzymes when Ca2+ levels rise

Answer

Calmodulin binds four calcium ions when intracellular Ca2+ rises, undergoes a conformational change, and then activates target proteins such as calmodulin-dependent protein kinases.

Question 3

Which type of RNA polymerase transcribes mRNA in eukaryotes?

Accepted Answer

RNA polymerase II

Answer

RNA polymerase II transcribes protein-coding genes to produce pre-mRNA (hnRNA) in eukaryotes; it also produces most snRNAs.

Question 4

In the lac operon, which molecule acts as the inducer to relieve repression?

Accepted Answer

Allolactose

Answer

Allolactose, a metabolite of lactose formed by beta-galactosidase, binds the lac repressor and causes a conformational change that releases it from the operator.

Question 5

Which of the following correctly describes a Schiff base in enzyme catalysis?

Accepted Answer

A covalent imine bond formed between an amino group and a carbonyl compound

Answer

A Schiff base (aldimine) is a covalent C=N bond formed when a primary amine (often enzyme lysine) reacts with a carbonyl group of a substrate, important in aminotransferase and aldolase reactions.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Biochemistry 4