Biochem Quiz 5 (Lectures #15 & #16)

Question 1

What is a Cofactor? (definition)

Answer 1

A cofactor is (in our context) usually a Metal or element that binds to an enzyme and gives it a unique property.

(This term could also include Coenzymes, but usually we’ll use it to talk about metals).

Question 2

Can a cofactor be bound to an enzyme in a prosthetic group? (such as iron or Heme)?

Answer 2

Yes, a cofactor can be bound to an enzyme in a prosthetic group.
BUT it can also be bound by covalent bonds, to the enzyme.

[So this just means being attached to a prosthetic group that is attached to the enzyme vs the cofactor being attached to the enzyme directly.]

Question 3

Definition of a Prosthetic Group?

Answer 3

A prosthetic group is a non-protein, tightly bound cofactor or coenzyme that is permanently attached to a protein, usually an enzyme. These groups are essential for the protein’s biological function, enabling the protein molecule to carry out its specific chemical reactions. Unlike loosely bound cofactors that can detach and reattach to the enzyme, prosthetic groups remain connected to the protein throughout the reaction process.

Question 4

What are the two main roles of Cofactors?

Answer 4

1: Substrate Alignment & Particle charge withdrawl.
(This one means that cofactors can do things like relieve unfavorable charges in the transition state, which can allow us to lower the delta G value because we can keep anions closer together without as much strain.)

2: Oxidation-reduction reactions.

Question 5

If we had all of the enzymes needed for metabolism in the human body, and just put them all together, why wouldn’t they be able to all function correctly.

Answer 5

Enzymes must function at the proper time and place to maintain healthy biochemistry.

(there is another card here that asks what the 5 methods of doing this are).

Question 6

What are the 5 methods of making sure that enzymes are coordinated spatiallty and temporally through five general regulatory mechanisms.

Answer 6

1. Alostery: {Regulatory molecules bind to the active site of an enzyme to either increase or decrease its functioning.}
2. Multiple forms of enzymes: {The multiple forms are isozymes of each other. Isozymes catalyze the SAME REACTION, but they respond to different regulatory molecules, as well as KM and Vmax values.
3. Reversible Covalent Modification: {Chemically modifying an enzyme site by adding or removing a molecule such as phosphate.}
4. Proteolytic Activation:
   {irreversibly making an enzyme activate, by cleavage of part of the peptide structure.}
5. Transcriptional Control:
   Gene transcription of the enzyme itself controls when it’s active or not.