MChem Master of Chemistry Biochemistry and Chemical Biology 2

Question 1

What distinguishes click chemistry reactions, such as the Cu-catalyzed azide-alkyne cycloaddition (CuAAC)?

Accepted Answer

They are modular, high-yielding, and produce only innocuous byproducts under mild conditions

Answer

They require harsh acidic or basic conditions

Answer

They exclusively form C–C bonds

Answer

They require protecting groups and multiple purification steps

Question 2

What is the principle behind FRET (Förster Resonance Energy Transfer) in biochemical assays?

Accepted Answer

Non-radiative energy transfers from a donor fluorophore to an acceptor when they are within ~10 nm of each other

Answer

Electrons transfer directly between two fluorophores via tunneling

Answer

Two fluorophores absorb the same photon simultaneously

Answer

A fluorophore transfers energy to oxygen, generating reactive singlet oxygen

Question 3

In proteomics, what is the purpose of tryptic digestion before mass spectrometry analysis?

Accepted Answer

To cleave proteins into peptides at Arg and Lys residues, generating a reproducible, manageable set of fragments

Answer

To denature proteins for better ionization

Answer

To remove glycosylation from proteins before analysis

Answer

To cross-link proteins to preserve their native state

Question 4

What is the chemical basis of disulfide bond formation in protein folding?

Accepted Answer

Two cysteine thiol groups (-SH) are oxidized to form a covalent S–S bridge

Answer

Two histidine residues coordinate a zinc ion to form a structural crosslink

Answer

A glutamine and asparagine residue condense to form an isopeptide bond

Answer

Serine and threonine hydroxyl groups condense to form ether linkages

Question 5

What is the function of ubiquitin in protein degradation?

Accepted Answer

It is conjugated to target proteins as a polyubiquitin tag that directs them to the 26S proteasome

Answer

It directly unfolds proteins for degradation by the proteasome

Answer

It serves as a cofactor that activates the proteasome's proteolytic subunits

Answer

It prevents protein aggregation by acting as a molecular chaperone

Question 6

What chemical feature distinguishes RNA from DNA that makes RNA more susceptible to alkaline hydrolysis?

Accepted Answer

The 2'-hydroxyl group of ribose acts as an intramolecular nucleophile to cleave the phosphodiester backbone

Answer

RNA has uracil instead of thymine, which is less stable

Answer

RNA has a single strand that is less protected from hydrolysis

Answer

RNA lacks the methyl group on pyrimidines that stabilizes DNA