Proteins & Amino Acids — NEET Biology MCQs with Solutions
Free NEET Biology Proteins & Amino Acids MCQs with step-by-step solutions (6 questions). Part of Biomolecules. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Proteins & Amino Acids · easy · theory
The number of amino acids that commonly occur in proteins is:
A. 4
B. 10
C. 64
D. 20 ✓ Correct
Solution: Twenty standard amino acids make up proteins; each has an amino group, carboxyl group, H and an R group on the α-carbon.
Q2 — Proteins & Amino Acids · easy · theory
The bond that links two amino acids in a protein is the:
A. Hydrogen bond
B. Phosphodiester bond
C. Peptide bond ✓ Correct
D. Glycosidic bond
Solution: A peptide (amide) bond forms between the –COOH of one amino acid and the –NH₂ of the next, with loss of water.
Q3 — Proteins & Amino Acids · medium · theory
The nature of an amino acid (acidic, basic or neutral) is decided by its:
A. Amino group
B. Carboxyl group
C. R group (side chain) ✓ Correct
D. Alpha carbon
Solution: The R group determines the chemical/functional character of the amino acid (e.g. glutamic acid = acidic, lysine = basic).
Q4 — Proteins & Amino Acids · medium · theory
Amino acids that cannot be synthesised by the human body and must be taken in the diet are called:
A. Essential amino acids ✓ Correct
B. Semi-essential amino acids
C. Non-essential amino acids
D. Secondary metabolites
Solution: Essential amino acids must be obtained from food; the body can synthesise non-essential ones.
Q5 — Proteins & Amino Acids · hard · theory
A zwitterion form of an amino acid exists at physiological pH because:
A. Both groups are neutral
B. The R group is always charged
C. It has no charge at any pH
D. The amino group is protonated (+) and the carboxyl group is ionised (−) simultaneously ✓ Correct
Solution: At neutral pH amino acids bear both a positive (–NH₃⁺) and a negative (–COO⁻) charge — the zwitterion (dipolar) form.
Q6 — Proteins & Amino Acids · hard · theory
The average molecular mass of an amino acid residue in a protein (~110 Da) is less than the free amino acid because:
A. Amino acids gain mass on polymerising
B. The R group is removed
C. A molecule of water is lost during each peptide bond formation ✓ Correct
D. Proteins contain no water
Solution: Peptide bond formation is a condensation (dehydration), so each residue is lighter than the free amino acid by ~18 Da.