CPC CPC Biochemistry & Biological Chemistry

Question 1

Which bond type is primarily responsible for the secondary structure (α-helix and β-sheet) of proteins?

Accepted Answer

Hydrogen bonds between backbone NH and C=O groups

Answer

Secondary structures are stabilized by hydrogen bonds between the peptide backbone's NH groups and carbonyl (C=O) groups at regular intervals along the chain, forming α-helices and β-sheets.

Question 2

In enzyme kinetics, the Michaelis constant (Km) represents:

Accepted Answer

Substrate concentration at which reaction velocity is half of Vmax

Answer

Km is the substrate concentration [S] at which the reaction velocity equals Vmax/2; a low Km indicates high enzyme affinity for the substrate.

Question 3

Which nucleotide base pairs with adenine (A) in DNA?

Accepted Answer

Thymine (T)

Answer

In DNA, adenine pairs with thymine via two hydrogen bonds (A=T), while guanine pairs with cytosine via three hydrogen bonds (G≡C), following Chargaff's base pairing rules.

Question 4

The citric acid cycle (Krebs cycle) primarily occurs in which cellular compartment?

Accepted Answer

Mitochondrial matrix

Answer

The citric acid cycle takes place in the mitochondrial matrix, where acetyl-CoA (from pyruvate oxidation) is fully oxidized to CO2, generating NADH, FADH2, and GTP.

Question 5

Which lipid class forms the basic structural component of biological cell membranes?

Accepted Answer

Phospholipids

Answer

Phospholipids form the lipid bilayer of cell membranes due to their amphipathic nature: hydrophilic phosphate head groups face aqueous environments while hydrophobic fatty acid tails face inward.

(CPC) Certified Professional Chemist Practice Test

(CPC) Certified Professional Chemist Practice Test

CPC CPC Biochemistry & Biological Chemistry