MChem Master of Chemistry Biochemistry and Chemical Biology 3

Question 1

What is the mechanism of action of cisplatin as an anticancer agent?

Accepted Answer

It forms intrastrand and interstrand platinum crosslinks on DNA, blocking replication and transcription

Answer

Cisplatin undergoes aquation to form a reactive species that crosslinks adjacent guanines on the same strand (1,2-d(GpG) intrastrand adducts), stalling DNA polymerase and triggering apoptosis.

Question 2

In NMR spectroscopy of biomolecules, what is the NOE (Nuclear Overhauser Effect) used to determine?

Accepted Answer

The 3D structure of proteins by measuring through-space distances between protons < 5 Å apart

Answer

The NOE provides distance restraints between protons within ~5 Å of each other, and these restraints are used with computational methods to determine solution-phase 3D protein structures.

Question 3

What is the key biochemical role of glutathione (GSH) in cellular protection?

Accepted Answer

It scavenges reactive oxygen species and detoxifies electrophilic xenobiotics via GSH-S-transferases

Answer

Glutathione (γ-Glu-Cys-Gly) acts as the cell's major antioxidant, reducing H2O2 via glutathione peroxidase and conjugating electrophiles via glutathione S-transferases for detoxification.

Question 4

What structural feature of phospholipid bilayers explains their selective permeability?

Accepted Answer

The hydrophobic hydrocarbon core creates an energetic barrier that strongly excludes charged and polar molecules

Answer

The hydrophobic bilayer interior (ΔG ~ +20 kcal/mol for ion transfer) is highly impermeable to ions and polar molecules, while nonpolar gases (O2, CO2) diffuse freely.

Question 5

In chemical biology, what is a 'warhead' in the context of covalent inhibitor drug design?

Accepted Answer

A reactive electrophilic group that forms a covalent bond with a nucleophilic residue in the target protein

Answer

Warheads (e.g., acrylamides, chloroacetamides) are reactive electrophiles that covalently modify active-site nucleophiles (e.g., Cys, Lys), providing irreversible or slow-reversible inhibition.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Biochemistry and Chemical Biology 3