Enzymes: Cofactors and Inhibitors

Question 1

Describe the types of multiple substrate enzyme mechanisms?

Answer 1

Sequential (2 types) - both substrates are bound prior to product formation includes: Random- either A or B can bind first or Ordered- A must bind prior to B binding

Ping-Pong- A binds and produces C prior to B binding and producing D

Question 2

What is the difference between a coenzyme and a cofactor?

Answer 2

Coenzyme- an organic molecule; vitamins

Cofactor- an inorganic element or compound; minerals

Question 3

Describe functions of different coenzymes

Answer 3

Coenzymes work by covalently binding to the enzymes active site and carry electrons through the reaction to allow it to take place

Question 4

Compare the different types of enzyme inhibitors.

Answer 4

Competitive- compete with substrate by binding to the enzymes active site Km + Vmax =
Uncompetitive- does not bind to the enzyme active site, instead it binds to a different site only after the substrate is bound Km & Vmax -
Noncompetitive- binds to different site than substrate either in the presence or absence of the substrate; has both competitive and uncompetitive characteristics (more uncompetitive than competitive) Km = Vmax -

Question 5

Explain feed-forward and feed-back enzymatic regulation.

Answer 5

Feed-forward: can either be inhibitory or activating and is the activation/inhibition of an enzyme by a precursor of the substrate of that enzyme.
Feed-back regulation: either inhibitory or activating and is the activation/inhibition of an enzyme by an end product of a biochemical pathway in which that enzyme plays a part.

Question 6

Describe the role of subunit dissociation and reversible phosphorylation on enzymatic function and control.

Answer 6

Some enzymes have separate regulatory subunits bound to them. An activating molecule will bind to the complex releasing the regulatory subunit and activating the enzyme.
Phosphorylating an enzyme will change the conformation and free up the active site for binding (activates it or turns it on). Dephosphorylating an enzyme will turn it off allowing control over the enzyme when it is and is not needed.