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

It inhibits DNA topoisomerase II, preventing strand religation

Answer

It intercalates between DNA base pairs, distorting the helix

Answer

It alkylates the N7 of guanine via an SN1 mechanism

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 primary sequence of a protein from its fragmentation pattern

Answer

The molecular weight of a protein from its diffusion coefficient

Answer

The pKa values of ionizable residues in the active site

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

It is a coenzyme for fatty acid elongation

Answer

It transports electrons in the mitochondrial electron transport chain

Answer

It regulates blood glucose by activating insulin receptor kinase

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 charged phosphate headgroups create pores that allow ion transport

Answer

Membrane proteins form a continuous impermeable seal

Answer

The fluid mosaic model requires lateral movement to transport molecules

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

The fluorescent reporter group on a probe molecule

Answer

The pharmacophore that determines binding specificity

Answer

A prodrug moiety that is cleaved in vivo to release the active drug

Question 6

What is the Ramachandran plot used for in protein structural analysis?

Accepted Answer

Displaying the allowed phi (φ) and psi (ψ) backbone dihedral angles of amino acid residues in a protein

Answer

Showing the distribution of amino acid compositions in a protein

Answer

Mapping the hydrophobic core residues of a folded protein

Answer

Illustrating the secondary structure assignment along the protein sequence