Biomolecules — Page 5 | NEET Chemistry

Q41

Feedback inhibition of an enzymatic reaction is caused by

A End product

B Substrate

C Enzyme

D Rise in temperature

Correct Answer

Option A

Solution

(a) Feedback inhibition is caused by the end product of an enzymatic pathway.

Q42

In which one of the following enzymes is copper necessarily associated as an activator?

A Carbonic anhydrase

B Tryptophanase

C Lactic dehydrogenase

D Tyrosinase

Correct Answer

Option D

Solution

(d) Tyrosinase is a copper-containing oxidase which oxidizes tyrosine to the pigment melanin.

Q43

The catalytic efficiency of two different enzymes can be compared by the

A formation of the product

B pH optimum value

C Km value

D molecular size of the enzyme

Correct Answer

Option C

Solution

(c) Km is inversely proportional to affinity of enzyme for its substrate and measures catalytic efficiency.

Q44

Which of the following statements regarding enzyme inhibition is correct?

A Competitive inhibition is seen when a substrate competes with an enzyme for binding to an inhibitor protein.

B Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme.

C Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate.

D Non-competitive inhibitors often bind to the enzyme irreversibly.

Correct Answer

Option B

Solution

(b) In competitive inhibition the inhibitor resembles the substrate and competes for the active site.

Q45

An organic substance bound to an enzyme and essential for its activity is called

A Holoenzyme

B Apoenzyme

C Isoenzyme

D Coenzyme

Correct Answer

Option D

Solution

(d) Coenzyme is an organic substance that enhances the action of an enzyme by binding with the protein molecule.

Q46

A competitive inhibitor of succinic dehydrogenase is

A Malonate

B Oxaloacetate

C m-ketoglutarate

D Malate

Correct Answer

Option A

Solution

(a) Malonate is a powerful inhibitor of cellular respiration as it competes with succinate for binding to succinic dehydrogenase.

Q47

Which of the following statements about enzymes is wrong?

A Enzymes require optimum pH and temperature for maximum activity

B Enzymes are denatured at high temperatures

C Enzymes are mostly proteins but some are lipids also

D Enzymes are highly specific

Correct Answer

Option C

Solution

(c) Almost all enzymes are proteins. Some nucleic acids behave like enzymes, called ribozymes.

Q48

Transition state structure of the substrate formed during an enzymatic reaction is:

A permanent but unstable

B transient and unstable

C permanent and stable

D transient but stable

Correct Answer

Option B

Solution

(b) Transition state structure formed during an enzymatic reaction is transient and unstable.

Q49

The essential chemical components of many coenzymes are:

A Nucleic acids

B Carbohydrates

C Vitamins

D Proteins

Correct Answer

Option C

Solution

(c) Many coenzymes contain vitamins as essential chemical components, e.g. NAD and NADP contain niacin.

Q50

Select the option which is not correct with respect to enzyme action:

A Substrate binds with enzyme at its active site.

B Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate.

C A non-competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate.

D Malonate is a competitive inhibitor of succinic dehydrogenase.

Correct Answer

Option B

Solution

(b) Inhibition of succinic dehydrogenase by malonate is a competitive inhibition and is reversible.