NEET (UG)

Practice Test 1 — Biomolecules

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

Alkaloids, rubber and antibiotics are examples of:

Solution: These are secondary metabolites.

Question 2

The bond between two amino acids in a protein is a:

Solution: Amino acids are linked by peptide bonds.

Question 3

The four-subunit structure of haemoglobin is its ___ structure:

Solution: Multiple subunits = quaternary structure.

Question 4

Starch gives a blue colour with iodine because it is:

Solution: Iodine fits inside the helical starch molecule.

Question 5

In DNA, adenine pairs with thymine through:

Solution: A=T has two hydrogen bonds.

Question 6

The pentose sugar in RNA is:

Solution: RNA contains ribose (DNA has deoxyribose).

Question 7

Which enzyme class catalyses hydrolysis reactions?

Solution: Hydrolases catalyse hydrolysis.

Question 8

An inactive protein part of an enzyme without its cofactor is the:

Solution: The apoenzyme is the protein part alone.

Section B — Assertion & Reason

Question 9

A: A DNA molecule rich in G≡C pairs is more stable to heat.
R: The G≡C pair is held by three hydrogen bonds, compared with two in A=T.

Solution: More hydrogen bonds per pair means greater thermal stability — R explains A.

Question 10

A: The effect of malonate on succinic dehydrogenase can be reversed by adding more succinate.
R: Malonate is a competitive inhibitor that competes with succinate for the active site.

Solution: Because the inhibition is competitive, excess substrate outcompetes the inhibitor — R explains A.

Question 11

A: Lipids are not regarded as true macromolecules.
R: Their molecular weights are very high, generally above 10,000.

Solution: A is true, but R is false — lipid MW is LOW (under ~800), which is why they are not macromolecules.

Question 12

A: Enzyme activity falls sharply above its optimum temperature.
R: High temperature denatures the enzyme's protein structure.

Solution: Denaturation destroys the active site, so activity drops — R explains A.