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Biomolecules — Class 11 MCQs with Answers

Class 11 CBSE Biology · Chapter 9

90 practice questions · 30 Easy · 30 Medium · 30 Hard · Updated

Jump to the 6 solved questions

Practise the most important Class 11 CBSE Biology questions from Chapter 9, "Biomolecules". You get 9 timed quizzes made from 90 NCERT-based MCQs, with answers and explanations. The questions are split into 30 Easy, 30 Medium and 30 Hard. Warm up on the basics, then move on to the exam-level questions that top scorers in CBSE & Maharashtra HSC Board exams, MHT-CET and NEET UG get right.

To score well in "Biomolecules", focus on diagrams, key terms and knowing NCERT line by line. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This helps you stay accurate when time is short, just as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.

Use this chapter for focused revision. Start with the Easy set to check your basics on Biomolecules, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Biology mastery score. Try the 6 sample questions below: tap an option to see the answer and a worked explanation. Sign in free to start practising.

Biomolecules — important questions & MCQs with answers (Class 11 Biology)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

  1. Q1 of 6Easy

    Building blocks of proteins:

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    Answer: Amino acids

    Explanation: Proteins are built entirely from the 20 standard amino acids joined by peptide bonds. Glucose is the monomer of carbohydrates and nucleotides build nucleic acids, not proteins.

  2. Q2 of 6Easy

    Biomolecules can be separated into acid-soluble and acid-insoluble pools by?

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    Answer: Trichloroacetic acid treatment then filtration

    Explanation: Grinding tissue in trichloroacetic acid and filtering separates biomolecules: the filtrate holds small acid-soluble molecules while the residue holds acid-insoluble macromolecules.

  3. Q3 of 6Medium

    Most enzymes are:

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    Answer: Proteins

    Explanation: Most enzymes are globular proteins whose folded shape creates the active site. A small class of RNA molecules called ribozymes also catalyse reactions, but proteins dominate.

  4. Q4 of 6Medium

    Three-dimensional folding of a polypeptide is termed?

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    Answer: Tertiary structure

    Explanation: Tertiary structure is the overall 3-D folding of a single polypeptide chain, stabilised by hydrogen, ionic, disulfide and hydrophobic bonds -- distinct from quaternary structure, which needs multiple chains.

  5. Q5 of 6Hard

    Assertion: Average composition of living tissue places water at the top by weight. Reason: Proteins are the most abundant macromolecule by weight.

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    Answer: Both true; R does NOT explain A

    Explanation: Water being most abundant by weight and proteins being the most abundant macromolecule are both independently true, but the reason water dominates is its role as universal solvent, not protein content -- so R does not explain A.

  6. Q6 of 6Hard

    Enzymes catalyse reactions by:

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    Answer: Lowering activation energy

    Explanation: Enzymes speed reactions by lowering the activation energy needed to reach the transition state, not by supplying extra energy or shifting the equilibrium point of the reaction.

Biomolecules notes: key concepts (Class 11 Biology)

Living cells are built from a small set of biomolecules. This chapter surveys carbohydrates, proteins, lipids and nucleic acids, their monomers and bonds, then turns to enzymes — protein catalysts whose activity, governed by active sites and inhibitors, follows predictable temperature, pH and substrate relationships.

Analysis of biomolecules
Acid-insoluble macromolecules (proteins, nucleic acids, polysaccharides) form the biomacromolecule pool; acid-soluble small metabolites under 1000 Da make the other pool.
Amino acids
Building blocks of proteins with amino, carboxyl, hydrogen and R groups on one carbon; the twenty standard types are zwitterionic and differ only in their side chain.
Top: the general structure of an α-amino acid, a carbon atom bonded to an amino group H₂N, a carboxyl group COOH, a side chain R and a hydrogen H. Bottom, linked by equilibrium arrows: the same molecule as a zwitterion, in which the carboxyl group has passed its proton to the amino group, giving H₃N⁺ with a positive charge and COO⁻ with a negative charge on the same molecule. Having both an acidic and a basic group makes amino acids amphoteric.
Proteins and peptide bond
Amino acids link by peptide bonds into polypeptides; proteins are the most abundant biomolecule, acting as enzymes, transporters, receptors, hormones and antibodies.
Top: two amino acids, H₂N–CHR–COOH and H₂N–CHR′–COOH. An arrow labelled minus H₂O points down to the dipeptide formed: H₂N–CH(R)–C(=O)–NH–CH(R′)–COOH, drawn as a zigzag chain. The –CO–NH– group in the middle, a carbon double-bonded to oxygen and single-bonded to an N–H, is shown in red and labelled peptide bond. It forms when the –COOH of the first amino acid and the –NH₂ of the second join and a molecule of water is lost.
Protein structure levels
Primary is the amino-acid sequence, secondary the helix or sheet folding, tertiary the 3-D shape, and quaternary the assembly of subunits, as in haemoglobin.
Carbohydrates
Polyhydroxy aldehydes or ketones; monosaccharides (glucose), disaccharides (sucrose) and polysaccharides such as starch (storage) and cellulose (structural).
Glycosidic bond
Monosaccharides join by glycosidic bonds; starch coils into a helix that holds iodine to give blue, whereas straight cellulose fibres show no such colour.
Maltose: two α-D-glucose rings, drawn as Haworth rings, side by side. C-1 of the left ring is joined through an oxygen atom (shown in red) to C-4 of the right ring, a C–O–C glycosidic linkage below the rings. It forms when the C-1 OH of one glucose and the C-4 OH of the next combine and a molecule of water is lost. The other OH groups and the CH₂OH group on each ring are unchanged; the right ring keeps a free OH at its C-1.
Lipids
Largely water-insoluble; fats are glycerol esterified with fatty acids, phospholipids with a phosphate head build membranes, and steroids act as hormones.
Nucleic acids
Polynucleotides of a nitrogen base, a pentose sugar and phosphate; DNA stores genetic information and RNA expresses it, linked by phosphodiester bonds.
Top: a nucleotide, the unit of DNA and RNA: a phosphate group P joined to a pentose sugar (a pentagon), which is joined to a nitrogenous base. Bottom: a short stretch of DNA, two strands running in opposite directions, one 5′ to 3′ downwards and the other 5′ to 3′ upwards. Bases on the two strands pair by hydrogen bonds, drawn as dashed lines: adenine A with thymine T by two, guanine G with cytosine C by three.
Enzyme nature
Almost all enzymes are proteins (a few are RNA ribozymes) that speed reactions by lowering activation energy and emerge unchanged, ready to be reused.
Active site and mechanism
Substrate binds a specific active-site pocket forming an enzyme-substrate complex; the induced-fit model says the site moulds itself around the substrate.
Three stages left to right, joined by arrows. First, an enzyme E with a pocket, the active site, cut into its surface, and a substrate S above it. Second, the substrate bound in the active site, which has moulded itself closely around it (induced fit): the enzyme–substrate complex ES. Third, the substrate has been changed into two products P that leave the active site, and the enzyme is free again, unchanged and ready to bind another substrate.
Factors affecting activity
Each enzyme has an optimum temperature and pH; extremes denature it. Rate climbs with substrate concentration until the active sites saturate at Vmax.
Three graphs of enzyme activity. Top left, activity against temperature: it rises to a peak at the optimum temperature and falls steeply beyond it as the enzyme is denatured. Top right, activity against pH: a bell-shaped curve with its peak at the optimum pH, falling on either side. Bottom, reaction velocity V against substrate concentration: V rises steeply at first and then levels off at the maximum velocity Vmax, drawn as a dashed line, once all the active sites are occupied.
Enzyme classification
Six classes by reaction type: oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases; many need cofactors, coenzymes or metal ions.
Competitive inhibition
An inhibitor resembling the substrate competes for the active site; malonate blocking succinate dehydrogenase is the example, reversed by adding more substrate.
An enzyme, succinic dehydrogenase, with its active site occupied by the inhibitor malonate, whose shape closely resembles that of the substrate succinate. The substrate, drawn beside it with the same V-shaped end, cannot bind because the active site is taken: its path is crossed out. Inhibitor and substrate compete for the same site, so adding more substrate reverses the inhibition.
Non-competitive inhibition
The inhibitor binds a site other than the active site, changing enzyme shape so substrate cannot be converted; adding more substrate does not relieve it.
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Biomolecules — FAQs

What are the key concepts in Class 11 Biology Biomolecules?+

Living cells are built from a small set of biomolecules. This chapter surveys carbohydrates, proteins, lipids and nucleic acids, their monomers and bonds, then turns to enzymes — protein catalysts whose activity, governed by active sites and inhibitors, follows predictable temperature, pH and substrate relationships. Key ideas include Analysis of biomolecules, Amino acids, Proteins and peptide bond, Protein structure levels, Carbohydrates, Glycosidic bond.

What does Class 11 Biology Chapter 9 (Biomolecules) cover on XamBaaz?+

It has 90 NCERT-based MCQs on "Biomolecules": 30 Easy, 30 Medium and 30 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, MHT-CET and NEET UG.

Are these "Biomolecules" questions free to practise?+

Yes. Sign in with Google to practise "Biomolecules" free. Full unlimited access is ₹1,999/year. One year from the day you pay. You stay in Class 11 till 31 March; on 1 April your account moves up to Class 12 and the rest of your year carries over. No chapter is charged separately.

How should I revise "Biomolecules" for the exam?+

Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.

Are these "Biomolecules" MCQs available with answers?+

Yes. 6 sample questions are on this page with answers: tap an option, or "Show answer", to see the correct option and a step-by-step explanation. Sign in free with Google to start practising, with instant scoring.

Is there negative marking in the "Biomolecules" quizzes?+

Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.

What are the important questions from Biomolecules (Class 11 Biology)?+

The questions that matter most test Analysis of biomolecules, Amino acids, Proteins and peptide bond, Protein structure levels, Carbohydrates, Glycosidic bond. This page shows 6 solved important MCQs with answers and explanations. Sign in to practise all 90 questions on the chapter as timed quizzes.

Is there an online quiz for Biomolecules?+

Yes — Class 11 Biology Biomolecules has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.

Are there question answers and extra questions for Biomolecules (Class 11 Biology)?+

Yes. This page has 6 solved questions on Biomolecules, each with the correct answer and a short explanation. Sign in to practise all 90 questions on the chapter as timed quizzes.

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