Biomolecules

Class 11

28 previous-year questions from this chapter every option and the correct answer, free · where the marks are

1. Carbohydrates, lipids, amino acids and proteins

Exam focus: NEET's favourite trap here is two different "most abundant" claims: protein is the most abundant biomolecule inside a living cell, but cellulose, a structural polysaccharide, is the most abundant organic compound in the entire biosphere — mixing up "in a cell" with "in nature" is exactly how this gets tested.

Biomolecules — Full Chapter in One Shot

PW NEET

Carbohydrates, lipids, amino acids and the four levels of protein structure, basics through PYQ level, in one sitting.

BotanyNEET 2024show ▾

Lecithin, a small molecular weight organic compound found in living tissues, is an example of:

A.Phospholipids✓
B.Glycerides
C.Carbohydrates
D.Amino acids

Solution

Lecithin is a phosphoglyceride — a glycerol backbone carrying two fatty acids and a phosphate-linked choline. It is the standard NCERT example of a phospholipid found in cell membranes.

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BotanyNEET 2024show ▾

Match List I with List II.

List I	List II
A. GLUT-4	I. Hormone
B. Insulin	II. Enzyme
C. Trypsin	III. Intercellular ground substance
D. Collagen	IV. Enables glucose transport into cells

Choose the correct answer from the options given below:

A.A-I, B-II, C-III, D-IV
B.A-II, B-III, C-IV, D-I
C.A-III, B-IV, C-I, D-II
D.A-IV, B-I, C-II, D-III✓

Solution

GLUT-4 transports glucose into cells (IV); insulin is a hormone (I); trypsin an enzyme (II); collagen the intercellular ground substance of connective tissue (III).

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BotanyNEET 2023show ▾

Cellulose does not form a blue colour with iodine because:

A.It is a disaccharide
B.It is a helical molecule
C.It does not contain complex helices and hence cannot hold iodine molecules✓
D.It breaks down when iodine reacts with it

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ZoologyNEET 2023show ▾

Given below are two statements: Statement I: A protein is imagined as a line, the left end represented by the first amino acid (C-terminal) and the right end represented by the last amino acid (N-terminal). Statement II: Adult human haemoglobin consists of 4 subunits (two subunits of

α

type and two subunits of

β

type). In the light of the above statements, choose the correct answer from the options given below:

A.Both Statement I and Statement II are true
B.Both Statement I and Statement II are false.
C.Statement I is true but Statement II is false.
D.Statement I is false but Statement II is true.✓

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ZoologyNEET 2022show ▾

Match List-I with List-II.

List-I (Biological molecules)	List-II (Biological functions)
(a) Glycogen	(i) Hormone
(b) Globulin	(ii) Biocatalyst
(c) Steroids	(iii) Antibody
(d) Thrombin	(iv) Storage product

Choose the correct answer from the options given below:

A.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)✓
B.(a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
C.(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
D.(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)

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ZoologyNEET 2022show ▾

A dehydration reaction links two glucose molecules to produce maltose. If the formula for glucose is

C_{6} H_{12} O_{6}

, then what is the formula for maltose?

A. $C_{12} H_{24} O_{11}$
B. $C_{12} H_{20} O_{10}$
C. $C_{12} H_{24} O_{12}$
D. $C_{12} H_{22} O_{11}$ ✓

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BotanyNEET 2022show ▾

The exoskeleton of arthropods is composed of:

A.Glucosamine
B.Cutin
C.Cellulose
D.Chitin✓

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BotanyNEET 2022show ▾

Read the following statements on lipids and find out the correct set of statements: (a) Lecithin found in the plasma membrane is a glycolipid (b) Saturated fatty acids possess one or more C=C bonds (c) Gingelly oil has a lower melting point, hence remains as oil in winter (d) Lipids are generally insoluble in water but soluble in some organic solvents (e) When a fatty acid is esterified with glycerol, monoglycerides are formed Choose the correct answer from the options given below:

A.(a), (b) and (d) only
B.(a), (b) and (c) only
C.(a), (d) and (e) only
D.(c), (d) and (e) only✓

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BotanyNEET 2021show ▾

Match List-I with List-II.

List-I	List-II
(a) Protein	(i) C=C double bonds
(b) Unsaturated fatty acid	(ii) Phosphodiester bonds
(c) Nucleic acid	(iii) Glycosidic bonds
(d) Polysaccharide	(iv) Peptide bonds

Choose the correct answer from the options given below:

A.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)✓
B.(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
C.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
D.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)

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ZoologyNEET 2021show ▾

Following are the statements with reference to 'lipids'. (a) Lipids having only single bonds are called unsaturated fatty acids (b) Lecithin is a phospholipid (c) Trihydroxypropane is glycerol (d) Palmitic acid has 20 carbon atoms including the carboxyl carbon (e) Arachidonic acid has 16 carbon atoms Choose the correct answer from the options given below:

A.(a) and (b) only
B.(c) and (d) only
C.(b) and (c) only✓
D.(b) and (e) only

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ZoologyNEET 2021show ▾

Identify the incorrect pair.

A.Alkaloids – Codeine
B.Toxin – Abrin
C.Lectins – Concanavalin A
D.Drugs – Ricin✓

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BotanyNEET 2021show ▾

Which of the following are not secondary metabolites in plants?

A.Morphine, codeine
B.Amino acids, glucose✓
C.Vinblastin, curcumin
D.Rubber, gums

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ZoologyNEET 2020show ▾

Identify the basic amino acid from the following.

A.Tyrosine
B.Glutamic acid
C.Lysine✓
D.Valine

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ZoologyNEET 2020show ▾

Match the following.

Description	Substance
(a) Inhibitor of catalytic activity	(i) Ricin
(b) Possesses peptide bonds	(ii) Malonate
(c) Cell wall material in fungi	(iii) Chitin
(d) Secondary metabolite	(iv) Collagen

Choose the correct option from the following:

A.(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)✓
B.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
C.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
D.(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)

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ZoologyNEET 2020show ▾

Identify the substances having a glycosidic bond and a peptide bond, respectively, in their structure.

A.Chitin, cholesterol
B.Glycerol, trypsin
C.Cellulose, lecithin
D.Inulin, insulin✓

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ZoologyNEET 2020show ▾

Which one of the following is the most abundant protein in animals?

A.Haemoglobin
B.Collagen✓
C.Lectin
D.Insulin

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ZoologyNEET 2019show ▾

Concanavalin A is:

A.An alkaloid
B.An essential oil
C.A lectin✓
D.A pigment

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2. Nucleic acids

Exam focus: The base-pairing fact NEET checks most is the hydrogen-bond count: A pairs with T (U in RNA) through two hydrogen bonds, G pairs with C through three — the extra bond is why GC-rich DNA is harder to melt, and swapping the two numbers is the standard wrong option.

Biomolecules: Nucleic Acids

Competition Wallah

Directly on-topic lecture on nucleic acid structure, nucleotides, the DNA double helix, and Chargaff's rules — no unrelated bundling.

ZoologyNEET 2025show ▾

Match List I with List II.

List I	List II
A. Adenosine	I. Nitrogen base
B. Adenylic acid	II. Nucleotide
C. Adenine	III. Nucleoside
D. Alanine	IV. Amino acid

Choose the option with all correct matches:

A.A-III, B-IV, C-II, D-I
B.A-III, B-II, C-IV, D-I
C.A-III, B-II, C-I, D-IV✓
D.A-II, B-III, C-I, D-IV

Solution

Adenosine is a nucleoside (III), adenylic acid a nucleotide (II), adenine a nitrogen base (I) and alanine an amino acid (IV).

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3. Enzymes: mechanism, factors, classification

Exam focus: Enzyme pH optima are not universal: pepsin works best in the stomach's strongly acidic pH while trypsin needs the small intestine's alkaline pH, so "neutral is optimal" is the wrong default to bring to a question naming a specific enzyme. Separately, a competitive inhibitor such as malonate on succinic dehydrogenase can be out-competed by raising substrate concentration; a non-competitive one, which doesn't bind the active site, cannot.

Biomolecules: Enzymes — Mechanism, Factors and Classification

Physics Wallah - Alakh Pandey

A lecture dedicated entirely to enzymes: mechanism/active site, factors affecting activity, and classification, with essentially no unrelated bundling.

BotanyNEET 2025show ▾

Which one of the following enzymes contains 'haem' as the prosthetic group?

A.RuBisCO
B.Carbonic anhydrase
C.Succinate dehydrogenase
D.Catalase✓

Solution

Catalase contains haem as its prosthetic group. Carbonic anhydrase and carboxypeptidase use zinc; RuBisCO needs $M g^{2 +}$ ; succinate dehydrogenase uses FAD.

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ZoologyNEET 2025show ▾

The protein portion of an enzyme is called:

A.Cofactor
B.Coenzyme
C.Apoenzyme✓
D.Prosthetic group

Solution

The protein part of a conjugated enzyme is the apoenzyme; with its cofactor it forms the active holoenzyme.

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BotanyNEET 2025show ▾

Name the class of enzyme that usually catalyses the following reaction:

S - G + S^{#} \to S + S^{#} - G

where G → a group other than hydrogen, S → a substrate, S# → another substrate.

A.Hydrolase
B.Lyase
C.Transferase✓
D.Ligase

Solution

Moving a group G from one substrate to another is the signature of a transferase. Hydrolases add water, lyases remove groups to form double bonds, and ligases join two molecules with ATP.

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BotanyNEET 2024show ▾

Inhibition of the succinic dehydrogenase enzyme by malonate is a classical example of:

A.Feedback inhibition
B.Competitive inhibition✓
C.Enzyme activation
D.Cofactor inhibition

Solution

Malonate closely resembles succinate, the substrate, and competes for the active site of succinic dehydrogenase — the textbook example of competitive inhibition.

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BotanyNEET 2024show ▾

The cofactor of the enzyme carboxypeptidase is:

A.Niacin
B.Flavin
C.Haem
D.Zinc✓

Solution

Carboxypeptidase requires zinc as its cofactor (a metal ion bound at the active site); niacin and flavin are coenzyme precursors, haem the prosthetic group of catalase and peroxidase.

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ZoologyNEET 2024show ▾

Match List I with List II.

List I	List II
A. Lipase	I. Peptide bond
B. Nuclease	II. Ester bond
C. Protease	III. Glycosidic bond
D. Amylase	IV. Phosphodiester bond

Choose the correct answer from the options given below:

A.A-III, B-II, C-I, D-IV
B.A-II, B-IV, C-I, D-III✓
C.A-IV, B-I, C-III, D-II
D.A-IV, B-II, C-III, D-I

Solution

Lipase breaks ester bonds (II); nucleases break phosphodiester bonds (IV); proteases break peptide bonds (I); amylase breaks glycosidic bonds (III).

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ZoologyNEET 2024show ▾

Regarding the catalytic cycle of enzyme action, select the correct sequential steps: A. Substrate–enzyme complex formation. B. Free enzyme ready to bind with another substrate. C. Release of products. D. Chemical bonds of the substrate broken. E. Substrate binding to the active site. Choose the correct answer from the options given below:

A.A, E, B, D, C
B.B, A, C, D, E
C.E, D, C, B, A
D.E, A, D, C, B✓

Solution

The catalytic cycle: substrate binds the active site (E) → enzyme–substrate complex forms (A) → the enzyme strains the substrate's bonds, which break (D) → products are released (C) → the free enzyme is ready for another substrate (B).

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BotanyNEET 2023show ▾

Malonate inhibits the growth of pathogenic bacteria by inhibiting the activity of:

A.Succinic dehydrogenase✓
B.Amylase
C.Lipase
D.Dinitrogenase

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ZoologyNEET 2023show ▾

Given below are two statements: Statement I: Low temperature preserves the enzyme in a temporarily inactive state, whereas high temperature destroys enzymatic activity because proteins are denatured by heat. Statement II: When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as a competitive inhibitor. In the light of the above statements, choose the correct answer from the options given below:

A.Both Statement I and Statement II are true.✓
B.Both Statement I and Statement II are false.
C.Statement I is true but Statement II is false.
D.Statement I is false but Statement II is true.

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ZoologyNEET 2019show ▾

Consider the following statements: (A) A coenzyme or metal ion that is tightly bound to an enzyme protein is called a prosthetic group. (B) A complete, catalytically active enzyme together with its bound prosthetic group is called an apoenzyme. Select the correct option.

A.Both (A) and (B) are true
B.(A) is true but (B) is false✓
C.Both (A) and (B) are false
D.(A) is false but (B) is true

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