FSc Part 1 Biology chapter 2: Biological molecules MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

25 exam-style questions on Biological molecules, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

25 questions · 2 topics · 10 per test

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What chapter 2 covers

Ten Biological molecules questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. The insulin molecule, whose amino acid sequence was first worked out by Frederick Sanger, contains

  1. A
    one chain of 51 amino acids
  2. B
    four chains of 30 amino acids each
  3. C
    two chains of 141 and 146 amino acids
  4. D
    two chains of 21 and 30 amino acids
Show answer

Answer: D. Insulin has 51 amino acids in two chains: A with 21 and B with 30, joined by disulphide bridges. 141 and 146 are the α and β chains of haemoglobin.

2. A sample of nucleic acid contains 18% adenine, 32% guanine, 18% thymine and 32% cytosine. It is most likely

  1. A
    single-stranded DNA
  2. B
    messenger RNA
  3. C
    transfer RNA
  4. D
    double-stranded DNA
Show answer

Answer: D. The presence of thymine rules out RNA (which has uracil), and the equal amounts A = T and G = C match base pairing across two strands, as in the double helix.

3. On a hot afternoon the water of a pond warms by only 2 °C, while the sand beside it warms by 15 °C in the same sunlight. Which property of water mainly explains this?

  1. A
    strong cohesion between its molecules
  2. B
    a high heat of vaporisation
  3. C
    a high specific heat capacity
  4. D
    a low density when it freezes
Show answer

Answer: C. Water absorbs a large amount of heat for each degree of temperature rise (high specific heat capacity), so it warms slowly and keeps body and habitat temperatures steady. Heat of vaporisation explains cooling by evaporation, not slow warming.

4. How many water molecules are released when one molecule of glycerol combines with three fatty acid molecules to form a triglyceride?

  1. A
    1
  2. B
    2
  3. C
    3
  4. D
    4
Show answer

Answer: C. Each of the three –OH groups of glycerol forms an ester bond with one fatty acid, and each ester bond releases one water molecule (condensation), so three waters are released. Two fatty acids plus a phosphate would make a phospholipid.

5. A molecule made of a protein combined with a nucleic acid, such as the chromatin of chromosomes, is a

  1. A
    glycoprotein
  2. B
    lipoprotein
  3. C
    glycolipid
  4. D
    nucleoprotein
Show answer

Answer: D. Nucleoproteins are nucleic acids bound to proteins (e.g. DNA with histones). Glycoproteins carry sugar chains; lipoproteins carry lipids.

6. How many peptide bonds are formed when a single unbranched polypeptide chain is built from 120 amino acids?

  1. A
    60
  2. B
    119
  3. C
    120
  4. D
    121
Show answer

Answer: B. Each peptide bond joins two neighbouring amino acids, so a chain of n amino acids has n − 1 bonds: 120 − 1 = 119. Each bond formation releases one water molecule (condensation).

7. Why can humans digest starch but not cellulose, although both are made of glucose?

  1. A
    human enzymes cannot break the β(1→4) links of cellulose
  2. B
    cellulose is made of fructose, which humans cannot digest
  3. C
    cellulose is branched at every glucose unit, so amylase cannot bind to it
  4. D
    starch contains amino acids, so it is digested by proteases
Show answer

Answer: A. Starch has α-glucose units, which amylase can hydrolyse; cellulose has β(1→4) links. Humans have no cellulase, so cellulose passes through as fibre.

8. Chitin, found in the exoskeleton of arthropods and the cell walls of fungi, is a polymer of

  1. A
    galacturonic acid
  2. B
    N-acetyl glucosamine
  3. C
    glycerol and fatty acids
  4. D
    amino acids joined by peptide bonds
Show answer

Answer: B. Chitin is a polysaccharide of N-acetyl glucosamine, a glucose derivative containing nitrogen. It is not a protein.

9. Why is water such a good solvent for ionic and polar substances?

  1. A
    its molecules are non-polar
  2. B
    it contains dissolved salts
  3. C
    it has a low boiling point
  4. D
    its molecules are polar and form hydrogen bonds
Show answer

Answer: D. The oxygen end of a water molecule is slightly negative and the hydrogen ends slightly positive, so water surrounds and separates ions and polar molecules.

10. Oils are liquid at room temperature mainly because their fatty acids are

  1. A
    unsaturated, with C=C double bonds
  2. B
    saturated, with only C–C single bonds
  3. C
    very long chains of glycerol
  4. D
    joined to the glycerol by peptide bonds
Show answer

Answer: A. Double bonds put kinks in the chains so they cannot pack tightly, lowering the melting point. Animal fats are mostly saturated and solid.

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Ways to practise this chapter

Biological molecules: questions students ask

How many Biological molecules MCQs are there?

25, each with the answer and a short explanation, across 2 topics: Water, carbohydrates and lipids, Proteins, nucleic acids and conjugated molecules. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Biology chapter 2 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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