Chemical Composition & Metabolites — NEET Biology MCQs with Solutions
Free NEET Biology Chemical Composition & Metabolites MCQs with step-by-step solutions (95 questions). Part of Biomolecules. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Chemical Composition & Metabolites · easy · theory
Compounds with molecular weight less than ~1000 Da found in the acid-soluble pool are called:
A. Polymers only
B. Macromolecules
C. Micromolecules (e.g. sugars, amino acids) ✓ Correct
D. Enzymes
Solution: Micromolecules (mol. wt < 1000 Da) form the acid-soluble pool; macromolecules (> 10 kDa) are in the acid-insoluble fraction.
Q2 — Chemical Composition & Metabolites · easy · theory
Alkaloids, flavonoids, rubber and essential oils are examples of:
A. Primary metabolites
B. Secondary metabolites ✓ Correct
C. Enzymes
D. Biomacromolecules
Solution: Secondary metabolites have no obvious direct role in normal physiology but are useful (drugs, pigments, defence).
Q3 — Chemical Composition & Metabolites · medium · theory
Amino acids, glucose, nucleotides and fatty acids are examples of:
A. Non-biological molecules
B. Only macromolecules
C. Secondary metabolites
D. Primary metabolites ✓ Correct
Solution: Primary metabolites have identifiable functions in normal physiological processes.
Q4 — Chemical Composition & Metabolites · medium · theory
The most abundant chemical in a living cell (and the medium of biochemical reactions) is:
A. Water ✓ Correct
B. Protein
C. Carbohydrate
D. Lipid
Solution: Water constitutes ~70–90% of cell mass and is the most abundant molecule; proteins are the most abundant macromolecule.
Q5 — Chemical Composition & Metabolites · hard · theory
When living tissue is ground with trichloroacetic acid and filtered, proteins, nucleic acids and polysaccharides are found in the:
A. Acid-soluble filtrate
B. Ash only
C. Acid-insoluble (retentate) fraction ✓ Correct
D. Gaseous phase
Solution: Macromolecules (proteins, nucleic acids, polysaccharides, lipids) form the acid-insoluble pool; micromolecules pass into the filtrate.
Q6 — Chemical Composition & Metabolites · hard · theory
Lipids, though sometimes below 800 Da, are found in the acid-INSOLUBLE (macromolecular) fraction because:
A. They have very high molecular weight
B. They dissolve in acid
C. They form part of membranes and come down as vesicles, not truly free molecules ✓ Correct
D. They are true polymers
Solution: Membrane lipids sediment as vesicular structures with the macromolecular fraction, an exception to the size rule.
Q7 — Chemical Composition & Metabolites · easy · numerical
Which of the following would be recovered from the acid-INSOLUBLE fraction when a tissue is ground with trichloroacetic acid?
A. Glucose
B. A free nucleotide
C. A free amino acid
D. Cellulose ✓ Correct
Solution: Cellulose is a polysaccharide macromolecule and settles in the acid-insoluble pool; glucose, nucleotides and free amino acids are small acid-soluble metabolites.
Q8 — Chemical Composition & Metabolites · easy · numerical
Excluding water, which class of compounds forms the single largest fraction of a cell's weight?
A. Proteins ✓ Correct
B. Nucleic acids
C. Carbohydrates
D. Lipids
Solution: In the average chemical composition of a cell, proteins (~10–15%) exceed carbohydrates (~3%), lipids (~2%) and nucleic acids (~5–7%) once water is excluded.
Q9 — Chemical Composition & Metabolites · easy · numerical
When a piece of living tissue is completely burnt, the residue (ash) that remains represents the:
A. inorganic elements and minerals such as calcium and phosphorus ✓ Correct
B. total carbohydrate content of the cell
C. nucleic acids of the cell
D. proteins and lipids of the cell
Solution: On complete combustion the organic compounds are lost as volatile gases (CO₂, water vapour, etc.), leaving behind the inorganic mineral elements as ash.
Q10 — Chemical Composition & Metabolites · easy · numerical
Biomacromolecules are distinguished from micromolecules chiefly because macromolecules have molecular weights that are:
A. in the range of ten thousand daltons and above ✓ Correct
B. less than that of a water molecule
C. exactly equal to eight hundred daltons
D. always less than one thousand daltons
Solution: Macromolecules (proteins, nucleic acids, polysaccharides) have molecular weights of ~10,000 Da and above, whereas micromolecules of the acid-soluble pool are below ~1000 Da.
Q11 — Chemical Composition & Metabolites · medium · numerical
Compared with the earth's crust, the human body shows a much higher relative abundance of:
A. silicon and aluminium
B. hydrogen, carbon and oxygen ✓ Correct
C. sodium and magnesium
D. iron and calcium
Solution: Although living organisms use the same elements as the non-living world, carbon, hydrogen and oxygen are far more abundant in the body than in the earth's crust, where silicon and aluminium dominate.
Q12 — Chemical Composition & Metabolites · medium · numerical
Which statement about secondary metabolites is correct?
A. They are only breakdown wastes with no use to the organism or to humans
B. They often serve ecological or defensive roles and have no direct part in normal physiological (primary) processes ✓ Correct
C. They include glucose, amino acids and nucleotides
D. They are essential intermediates of respiration and photosynthesis
Solution: Secondary metabolites (alkaloids, pigments, rubber, toxins, etc.) usually have ecological, defensive or human-welfare uses but are not part of the basic metabolic pathways that primary metabolites drive.
Q13 — Chemical Composition & Metabolites · medium · numerical
Which of the following correctly matches a metabolite with its category?
A. Morphine–pigment, Ricin–lectin, Concanavalin A–toxin, Carotenoid–alkaloid
B. Morphine–alkaloid, Ricin–toxin, Concanavalin A–lectin, Carotenoid–pigment ✓ Correct
C. Morphine–toxin, Ricin–pigment, Concanavalin A–alkaloid, Carotenoid–lectin
D. Morphine–lectin, Ricin–alkaloid, Concanavalin A–pigment, Carotenoid–toxin
Solution: Morphine is an alkaloid, ricin is a plant toxin, concanavalin A is a lectin, and carotenoids are pigments — all classes of secondary metabolites.
Q14 — Chemical Composition & Metabolites · medium · numerical
Assertion (A): Glucose, amino acids and nucleotides are primary metabolites. Reason (R): They have identifiable functions and play known roles in normal physiological processes.
A. A is true but R is false
B. Both A and R are true and R is the correct explanation of A ✓ Correct
C. Both A and R are true but R is not the correct explanation of A
D. A is false but R is true
Solution: Primary metabolites are so classified precisely because their roles in normal metabolism are identifiable; hence R correctly explains A.
Q15 — Chemical Composition & Metabolites · medium · numerical
Which of the following is NOT a micromolecule of the acid-soluble pool?
A. An amino acid
B. A polysaccharide such as starch ✓ Correct
C. A nucleotide
D. Glucose
Solution: Starch is a macromolecule found in the acid-insoluble fraction; glucose, amino acids and nucleotides are small acid-soluble metabolites.
Q16 — Chemical Composition & Metabolites · medium · numerical
Consider the statements: (i) Carotenoids and anthocyanins are pigments. (ii) Morphine and codeine are alkaloids. (iii) Vitamins are secondary metabolites. (iv) Gums and rubber are polymeric secondary substances. Which are correct?
A. (i), (iii) and (iv)
B. (i), (ii) and (iii)
C. (ii), (iii) and (iv)
D. (i), (ii) and (iv) ✓ Correct
Solution: Pigments, alkaloids and polymeric substances (gums, rubber) are recognised secondary metabolites; vitamins are not classed as secondary metabolites.
Q17 — Chemical Composition & Metabolites · medium
Read the following statements and find out the incorrect statement.
A. Some secondary metabolites have ecological significance.
B. Flavonoids, antibiotics, coloured pigments and lecithin are secondary metabolites. ✓ Correct
C. Secondary metabolites are found in plant, fungal and microbial cells and we do not understand the role of these secondary metabolites in host organisms.
D. Many secondary metabolites like rubbers, drugs, spices, scents and pigments are useful to human welfare.
Solution: Lecithin is a phospholipid (a primary metabolite/membrane lipid), not a secondary metabolite, making statement 4 incorrect.
Q18 — Chemical Composition & Metabolites · medium
Assertion: The acid soluble pool represents roughly the cytoplasmic composition. Reason: The macromolecules from cytoplasm and organelles become the acid insoluble fraction.
A. Both assertion and reason are true and the reason is the correct explanation of the assertion.
B. Both assertion and reason are true, but reason is not the correct explanation of the assertion. ✓ Correct
C. Assertion is true, but reason is false.
D. Both assertion and reason are false.
Solution: Both statements are true, but the reason describes the acid-insoluble fraction and does not directly explain why the acid-soluble pool reflects cytoplasmic composition.
Q19 — Chemical Composition & Metabolites · medium
Assertion: Secondary metabolites are produced in small quantities and their extraction from the plant is difficult and expensive. Reason: Secondary metabolites can be commercially produced by using tissue culture technique.
A. Both assertion and reason are false.
B. Assertion is true, but reason is false.
C. Both assertion and reason are true, but reason is not the correct explanation of the assertion. ✓ Correct
D. Both assertion and reason are true and the reason is the correct explanation of the assertion.
Solution: Both statements are true, but tissue-culture production is an alternative solution and does not directly explain why extraction is difficult and expensive.
Q20 — Chemical Composition & Metabolites · medium
Statement I: All the elements present in a sample of earth's crust are also present in a sample of living tissue. Statement II: Scientists have found thousands of organic compounds in the acid-soluble pool.
A. Both statement I and II are correct ✓ Correct
B. Only statement II is correct
C. Only statement I is correct
D. Both statement I and II are incorrect
Solution: Both statements are correct. On elemental analysis all elements of earth's crust are also found in living tissue, and thousands of organic compounds occur in the acid-soluble pool (the low molecular weight fraction).
Q21 — Chemical Composition & Metabolites · medium
Statement I: The most exciting aspect of chemistry deals with isolating thousands of compounds, small and big, from living organisms, determining their structure and if possible synthesising them. Statement II: Some secondary metabolites have ecological importance.
A. Both statement I and II are correct ✓ Correct
B. Only statement I is correct
C. Both statement I and II are incorrect
D. Only statement II is correct
Solution: Both statements are correct. Analytical biochemistry isolates and characterises compounds from living organisms, and many secondary metabolites (e.g. pigments, alkaloids, toxins) have ecological importance.
Q22 — Chemical Composition & Metabolites · medium
Match the component with its percentage of total cellular content. Column I: i. Nucleic acid, ii. Carbohydrate, iii. Protein, iv. Lipid. Column II: a. 5-7, b. 3, c. 10-15, d. 2.
A. i-a, ii-d, iii-b, iv-c
B. i-d, ii-b, iii-c, iv-a
C. i-a, ii-b, iii-c, iv-d ✓ Correct
D. i-b, ii-a, iii-c, iv-d
Solution: Nucleic acid ~5-7% (a), carbohydrate ~3% (b), protein ~10-15% (c), lipid ~2% (d). Hence i-a, ii-b, iii-c, iv-d.
Q23 — Chemical Composition & Metabolites · medium
Match the secondary metabolite (Column I) with its category (Column II). Column I: i. Codeine, ii. Abrin, iii. Concanavalin-A, iv. Vinblastin, v. Gums. Column II: a. Lectins, b. Polymeric substances, c. Drugs, d. Alkaloids, e. Toxins.
A. i-d, ii-c, iii-a, iv-e, v-b
B. i-a, ii-b, iii-c, iv-d, v-e
C. i-d, ii-e, iii-a, iv-c, v-b ✓ Correct
D. i-d, ii-e, iii-c, iv-a, v-b
Solution: Codeine is an alkaloid (d), abrin is a toxin (e), concanavalin-A is a lectin (a), vinblastin is a drug (c), and gums are polymeric substances (b). Hence i-d, ii-e, iii-a, iv-c, v-b.
Q24 — Chemical Composition & Metabolites · medium
Match Column I (component) with Column II (% of the total cellular mass). Column I: a. Ions, b. Lipids, c. Carbohydrates, d. Nucleic acids, e. Proteins. Column II: i. 1, ii. 2, iii. 3, iv. 5-7, v. 10-15.
A. a-ii, b-iii, c-i, d-v, e-iv
B. a-i, b-ii, c-iii, d-iv, e-v ✓ Correct
C. a-iii, b-i, c-ii, d-iv, e-v
D. a-iv, b-ii, c-iii, d-v, e-i
Solution: Ions ~1% (i), lipids ~2% (ii), carbohydrates ~3% (iii), nucleic acids ~5-7% (iv), proteins ~10-15% (v). Hence a-i, b-ii, c-iii, d-iv, e-v.
Q25 — Chemical Composition & Metabolites · medium
Match Column I with Column II. Column I: A. Pigments, B. Toxins, C. Alkaloids, D. Lectins. Column II: (i) Abrin, ricin, (ii) Concanavalin A, (iii) Carotenoids, (iv) Morphine, codeine.
A. A-(i), B-(ii), C-(iii), D-(iv)
B. A-(iv), B-(iii), C-(i), D-(ii)
C. A-(ii), B-(iv), C-(i), D-(iii)
D. A-(iii), B-(i), C-(iv), D-(ii) ✓ Correct
Solution: Pigments = carotenoids (iii), toxins = abrin, ricin (i), alkaloids = morphine, codeine (iv), lectins = concanavalin A (ii). Hence A-(iii), B-(i), C-(iv), D-(ii).
Q26 — Chemical Composition & Metabolites · medium
Match the following. Column I: (i) Alkaloid, (ii) Essential oils, (iii) Toxins, (iv) Drugs. Column II: (I) Vinblastin, curcumin, (II) Morphine, codein, (III) Lemon grass oil, (IV) Abrin, ricin.
A. (i)-(II), (ii)-(III), (iii)-(IV), (iv)-(I) ✓ Correct
B. (i)-(III), (ii)-(II), (iii)-(I), (iv)-(IV)
C. (i)-(III), (ii)-(II), (iii)-(IV), (iv)-(I)
D. (i)-(II), (ii)-(III), (iii)-(I), (iv)-(IV)
Solution: Alkaloid = morphine, codein (II), essential oils = lemon grass oil (III), toxins = abrin, ricin (IV), drugs = vinblastin, curcumin (I). Hence (i)-(II), (ii)-(III), (iii)-(IV), (iv)-(I).
Q27 — Chemical Composition & Metabolites · medium
Match List-I with List-II.
List-I: (1) Protein, (2) Unsaturated fatty acid, (3) Nucleic acid, (4) Polysaccharide.
List-II: (I) C=C double bonds, (II) Phosphodiester bond, (III) Glycosidic bonds, (IV) Peptide bonds.
A. (1)-(II), (2)-(I), (3)-(IV), (4)-(III)
B. (1)-(IV), (2)-(III), (3)-(I), (4)-(II)
C. (1)-(IV), (2)-(I), (3)-(II), (4)-(III) ✓ Correct
D. (1)-(I), (2)-(IV), (3)-(III), (4)-(II)
Solution: Proteins are joined by peptide bonds (IV); unsaturated fatty acids have C=C double bonds (I); nucleic acids are linked by phosphodiester bonds (II); polysaccharides are joined by glycosidic bonds (III).
Q28 — Chemical Composition & Metabolites · medium
Which of the following are not polymeric?
A. Proteins
B. Lipids ✓ Correct
C. Polysaccharides
D. Nucleic acids
Solution: Proteins (polymers of amino acids), polysaccharides (of sugars) and nucleic acids (of nucleotides) are macromolecular polymers. Lipids are not true polymers; they are relatively small molecules.
Q29 — Chemical Composition & Metabolites · medium
Match List-I with List-II.
List-I: (1) Terpenoids, (2) Lectins, (3) Alkaloids, (4) Toxins.
List-II: (I) Codeine, (II) Diterpenes, (III) Ricin, (IV) Concanavalin A.
A. (1)-(II), (2)-(IV), (3)-(I), (4)-(III) ✓ Correct
B. (1)-(II), (2)-(I), (3)-(IV), (4)-(III)
C. (1)-(II), (2)-(III), (3)-(I), (4)-(IV)
D. (1)-(II), (2)-(IV), (3)-(III), (4)-(I)
Solution: Terpenoids include diterpenes (II); lectins include concanavalin A (IV); alkaloids include codeine (I); toxins include ricin (III).
Q30 — Chemical Composition & Metabolites · medium
Which of the following is not a secondary metabolite?
A. Anthocyanin
B. Morphine
C. Lecithin ✓ Correct
D. Curcumin
Solution: Anthocyanin (pigment), curcumin and morphine (alkaloid) are secondary metabolites. Lecithin is a phospholipid, a primary metabolite/structural component of membranes.