Question

Feedback inhibition of enzyme is influenced by
A. Enzyme
B. External factors
C. End product
D. Substrate

Answer 1

Hint: Nearly all chemical reactions in the biological systems are catalysed by highly specific protein catalysts called enzymes. Enzymes are biological catalysts. Metabolic processes in the body are catalysed by enzymes. Enzymes occur in all living cells in the animal and plant body.

Complete answer:
Enzyme Inhibition: Enzyme action can be inhibited in four different ways:

1.Denaturation of Proteins- All enzymes are thermolabile. At a high temperature denaturation of protein results in an irreversible inhibition of enzyme action.

2.Competitive Inhibition- Competition occurs between the substrate and inhibitor for binding to the active site of an enzyme. Such inhibition is reversible by increasing the substrate concentration relative to that of the inhibitor.
a.Competitive inhibitors are reversible inhibitors that bind to the active site. The substrate is then prevented from binding to the same active site.
b.A typical example of competitive inhibition involves the enzyme succinate dehydrogenase, which catalyses the oxidation of succinate in mitochondria.
c.The activity of succinic dehydrogenase is inhibited by malonate, glutarate or otalate that resemble succinate in structure.

3.Non-competitive Inhibition- This is another reversible inhibition in which the inhibitor and substrate can bind simultaneously to an enzyme molecule.
a.This means that their binding sites do not overlap. Non-competitive inhibitors do not resemble an enzyme substrate and, hence, do not compete with substrates for binding to active sites.
b.An example of non-competitive inhibitor is cyanide, which binds to iron, kills an animal by inhibiting cytochrome oxidase, a mitochondrial enzyme essential for cellular respiration

4.Allosteric Modulation or Feedback Inhibition- Feed back inhibition of enzymes is influenced by the end product.
a.Some allosteric enzymes which catalyse metabolic pathways are regulated internally. b.Enzyme inhibition caused by a product of enzyme catalysed reaction is feedback inhibition.
c.Hexokinase which changes glucose to glucose 6-phosphate in glycolysis shows feedback inhibition Glucose-6-phosphate, the end product can inhibit hexokinase activity.

Hence, the correct answer is option (C)

Note: Mechanism of enzyme action:
Specificity: The specificity of an enzyme is determined by:
1.The functional groups of the substrate (or product).
2.The functional groups of the enzyme and its cofactors.
3.The proximity of these various functional groups physically.