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

Click reactions are defined by their high efficiency, selectivity, and bioorthogonality, making them ideal for labeling biomolecules in living cells.

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

FRET occurs via dipole-dipole coupling between a donor and acceptor fluorophore; its efficiency falls off as the inverse 6th power of distance, making it a molecular ruler for ~1–10 nm distances.

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

Trypsin cleaves specifically after Arg and Lys residues (except before Pro), generating peptides in the 500–3000 Da range optimal for LC-MS/MS identification.

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

Disulfide bonds form when two cysteine thiol groups lose electrons (oxidation) in the oxidizing environment of the ER lumen, catalyzed by protein disulfide isomerase (PDI).

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

A cascade of E1 (activating), E2 (conjugating), and E3 (ligase) enzymes attach polyubiquitin chains (typically Lys48-linked) to substrates, marking them for 26S proteasomal degradation.

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Practice Test

MChem Master of Chemistry Biochemistry and Chemical Biology 2