1 Feedback inhibition covalent modification and allosteric r

1. Feedback inhibition, covalent modification, and allosteric regulation are all examples of

a. compartmentalization

b. regulation of gene expression

c. posttranslational regulation

d. metabolic channeling

2. A molecule that binds noncovalently to an enzyme at the active site and thereby prevents a substrate from binding and reacting is a(n) __________ inhibitor.

1. competitive

2. noncompetitive

3. allosteric

4. reversible

Solution

Answer :

Question number 1 : The correct answer is 4 (metabolic channeling)

Question number 2 : The correct answer is 1(competitive)

Explanation : Competitive inhibitors competes and binds to the enzyme active site since it is structurally similar to enzymes substrate binds to enzyme active site. When an enzyme that follows Michaelis-Menten kinetics is treated with a competitive inhibitor, its K_m increases (affinity towards substrate decreases) and V_max unaffected. A competitive inhibitor diminishes the rate of catalysis by reducing the proportion of enzyme molecules bound to substrate.

Examples: Melanoate is a competitive inhibitor of succinate for the active site on SDH enzymes. Methotrxate is a competitive inhibitor of dihydrofolate for the enzyme Dihydrofolate reductase enzyme active site.