Biochemistry Flashcards
7 cards from real PCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Biochemistry flashcards as text
During beta-oxidation of a 16-carbon saturated fatty acid (palmitate), how many acetyl-CoA molecules are produced?
Answer: 8
A 16-carbon fatty acid undergoes 7 rounds of beta-oxidation, yielding 8 acetyl-CoA molecules, 7 FADH2, and 7 NADH.
Which of the following best describes the role of calmodulin in cellular signaling?
Answer: It is a calcium-binding protein that activates target enzymes when Ca2+ levels rise
Calmodulin binds four calcium ions when intracellular Ca2+ rises, undergoes a conformational change, and then activates target proteins such as calmodulin-dependent protein kinases.
Which type of RNA polymerase transcribes mRNA in eukaryotes?
Answer: RNA polymerase II
RNA polymerase II transcribes protein-coding genes to produce pre-mRNA (hnRNA) in eukaryotes; it also produces most snRNAs.
In the lac operon, which molecule acts as the inducer to relieve repression?
Answer: Allolactose
Allolactose, a metabolite of lactose formed by beta-galactosidase, binds the lac repressor and causes a conformational change that releases it from the operator.
Which of the following correctly describes a Schiff base in enzyme catalysis?
Answer: A covalent imine bond formed between an amino group and a carbonyl compound
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.
Glucokinase (hexokinase IV) differs from hexokinase I primarily because it:
Answer: Has a high Km for glucose and is not inhibited by its product glucose-6-phosphate
Glucokinase has a high Km (~10 mM) for glucose and is not subject to product inhibition, allowing hepatocytes to act as a glucose buffer by phosphorylating glucose only when blood glucose is high.
Which bond links nucleotides together in a DNA strand?
Answer: 3',5'-phosphodiester bond
Adjacent nucleotides in a DNA strand are connected by phosphodiester bonds formed between the 3'-hydroxyl of one sugar and the 5'-phosphate of the next.