BiomoleculesNEET MCQs with solutions
Biomolecules explains what living tissue is made of — from small sugars and amino acids to proteins, polysaccharides, nucleic acids and enzymes. NEET questions here test bonds, structures and examples, so knowing which molecule does what, and which bond joins it, is the key.
- Class
- 11 Biology
- Free on this page
- 24 questions
- In the RankUp app
- 579 questions
- ELITE questions
- 57
- NCERT topics
- 8
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1What are Biomolecules
Which of the following is a micromolecule likely to be found in the acid-soluble pool of living tissue homogenate?
Not quite — the answer is B.
Glucose is a small molecule (MW ~180 Da) that passes through the filter into the acid-soluble fraction. DNA, cellulose, and haemoglobin are all macromolecules retained in the acid-insoluble fraction.
Q2What are Biomolecules
After igniting a piece of living tissue completely, the ash residue represents which component of the original tissue?
Not quite — the answer is D.
Complete combustion destroys all organic matter (C, H, O, N exit as CO₂, H₂O, N₂). What remains is inorganic ash — mineral elements like Ca, Mg, K, Na, Fe, Zn, Mn — confirming the inorganic elemental content of living tissue.
Q3What are Biomolecules
Which element is most abundant by mass in living organisms?
Not quite — the answer is C.
Oxygen is the most abundant element by mass in living organisms because water (H₂O) alone constitutes 70–90% of cell mass, and oxygen is 89% of water's mass. This is a classic NEET trap — most students incorrectly select carbon, assuming it dominates organic molecules.
Q4Primary and Secondary Metabolites
A plant compound functions in herbivore defence and has no direct role in the plant's growth or reproduction. It is best categorised as:
Not quite — the answer is C.
Compounds not required for growth/reproduction but serving ecological roles — such as herbivore deterrence — are definitively secondary metabolites. Options A, B, and D all describe categories of primary metabolites.
Q5Primary and Secondary Metabolites
A compound isolated from opium poppy shows analgesic properties and contains nitrogen. It is most likely classified as:
Not quite — the answer is B.
Morphine-type compounds are nitrogen-containing alkaloids — secondary metabolites with pharmacological activity but no role in the producer's own primary metabolism. Options A, C, and D all describe primary metabolite categories, not alkaloids.
Q6Primary and Secondary Metabolites
Which of the following processes is exclusively associated with primary metabolites and cannot involve secondary metabolites?
Not quite — the answer is B.
Glycolysis involves exclusively primary metabolites — glucose, pyruvate, ATP, NAD⁺ — and is a universal energy-generating pathway. Defence (Option A), petal pigmentation (Option C), and antibiotic production (Option D) all involve secondary metabolites.
Q7Biomacromolecules
Which bond joins monosaccharide units in polysaccharides?
Not quite — the answer is D.
Glycosidic bonds are formed between the anomeric carbon of one sugar and a hydroxyl group of another, with loss of water. Peptide bonds link amino acids; phosphodiester bonds link nucleotides; disulfide bonds link cysteine residues in proteins.
Q8Biomacromolecules
Which level of protein structure is directly stabilized by disulfide bonds between cysteine residues?
Not quite — the answer is C.
Disulfide bonds are covalent linkages between sulfhydryl groups of cysteine residues, stabilizing tertiary structure by holding distant parts of the polypeptide chain together. Secondary structure is maintained by hydrogen bonds between backbone atoms; primary structure is held by peptide bonds.
Q9Biomacromolecules
Which of the following correctly distinguishes deoxyribose from ribose in nucleic acids?
Not quite — the answer is B.
Deoxyribose (in DNA) has a hydrogen atom at the 2′ carbon where ribose (in RNA) has a hydroxyl (–OH) group. This single difference makes DNA more chemically stable than RNA and is the basis for the "deoxy" prefix.
Q10Proteins
Which structural level of protein organisation refers to the linear sequence of amino acids joined by peptide bonds?
Not quite — the answer is B.
Primary structure is defined as the specific sequence of amino acids in the polypeptide chain, held together by covalent peptide bonds. All higher structures are dependent on this sequence.
Q11Proteins
Hydrolysis of peptide bonds in a protein directly disrupts which level of structure?
Not quite — the answer is C.
The primary structure IS the sequence of amino acids linked by peptide bonds — breaking them destroys the primary structure. All higher structures collapse as a consequence, but the direct effect is on primary structure.
Q12Proteins
Which factor would most specifically disrupt ionic interactions in a protein without primarily targeting other bond types?
Not quite — the answer is D.
Extreme pH alters the ionisation states of acidic and basic R-groups (e.g., -COO− and -NH3+), directly abolishing the charge-charge (ionic) attractions. Moderate heat primarily disrupts hydrophobic interactions and H-bonds first.
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Get RankUp on Google PlayQ13Carbohydrates
Which of the following sugars is a pentose?
Not quite — the answer is D.
Ribose contains five carbon atoms and is an aldopentose, critical in RNA structure. Glucose, Fructose, and Galactose are all hexoses.
Q14Carbohydrates
Which polysaccharide is composed of N-acetylglucosamine units linked by β-1,4 glycosidic bonds?
Not quite — the answer is C.
Chitin is a homopolysaccharide of N-acetylglucosamine with β-1,4 linkages, forming the exoskeleton of arthropods and fungal cell walls. Cellulose is also β-1,4 linked but uses glucose, not N-acetylglucosamine.
Q15Carbohydrates
Which change would convert a reducing disaccharide into a non-reducing one?
Not quite — the answer is A.
If the free anomeric carbon forms a glycosidic bond, no free carbonyl group remains, abolishing reducing property — exactly as in sucrose. Phosphate addition and polymerisation do not inherently eliminate anomeric freedom.
Q16Lipids
A long-chain fatty acid esterified with a long-chain monohydric alcohol is classified as:
Not quite — the answer is D.
Waxes are defined as esters of long-chain fatty acids and long-chain monohydric alcohols. They are harder and less reactive than triglycerides and serve protective roles (plant cuticle, ear wax, bee honeycomb).
Q17Lipids
In aqueous solution, a phospholipid molecule orients itself such that:
Not quite — the answer is D.
The amphipathic nature of phospholipids drives spontaneous orientation: polar heads interact favourably with water via H-bonds while nonpolar tails minimise contact with water by clustering inward.
Q18Lipids
Which of the following best explains why trans unsaturated fatty acids raise melting point more than cis unsaturated fatty acids?
Not quite — the answer is B.
Trans double bonds place the two carbon segments on opposite sides, keeping the chain relatively linear — allowing closer packing and higher melting points. Cis bonds place segments on the same side, creating kinks that disrupt packing.
Q19Nucleic Acids
Which sugar is present in RNA?
Not quite — the answer is B.
RNA contains ribose (with 2′-OH group); DNA contains deoxyribose (lacking the 2′-OH). This structural difference makes RNA less stable than DNA.
Q20Nucleic Acids
Which of the following is responsible for maintaining the complementarity between the two strands of DNA?
Not quite — the answer is B.
Hydrogen bonds (2 for A-T; 3 for G-C) between complementary purine-pyrimidine pairs hold the two strands together. These are non-covalent, making strand separation possible during replication.
Q21Nucleic Acids
Which of the following sequences of events correctly represents the components assembling into a nucleotide?
Not quite — the answer is A.
A nucleoside is formed first (base + sugar via glycosidic bond); addition of phosphate group then forms a nucleotide. This stepwise understanding is tested in NEET to trap students who conflate nucleoside and nucleotide assembly.
Q22Enzymes
Which of the following correctly classifies enzymes that catalyse oxidation-reduction reactions?
Not quite — the answer is A.
NCERT classifies enzymes into six types; oxidoreductases specifically catalyse oxidation-reduction reactions (e.g., dehydrogenases, oxidases). Lyases remove groups without hydrolysis, ligases join molecules, and transferases transfer functional groups — none involve redox.
Q23Enzymes
Enzyme-substrate complex formation is essential because it:
Not quite — the answer is C.
The ES complex positions the substrate precisely at the active site, reducing activation energy by stabilising the transition state. Enzymes do not alter the equilibrium constant (ΔG of reaction) — they only increase the rate of reaching equilibrium.
Q24Enzymes
Which of the following correctly explains the high substrate specificity of enzymes?
Not quite — the answer is A.
The specific arrangement of amino acid residues at the active site creates a unique geometric and chemical environment that only accommodates a substrate of complementary shape and charge. Option B is incorrect — enzyme-substrate interactions are typically non-covalent and transient.
ELITE question · AIR under 50 level
This chapter has 57 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appBiomolecule facts to remember
Quick revision: most questions in this chapter test these facts.
| Topic | Key fact |
|---|---|
| Most abundant chemical in living organisms | Water |
| Acid-soluble pool | Small molecules below about 1000 Da — amino acids, sugars, nucleotides |
| Acid-insoluble fraction | Proteins, nucleic acids, polysaccharides — and lipids, which form vesicles |
| Most abundant protein | Collagen in the animal world; RuBisCO in the whole biosphere |
| Bonds | Peptide bond (amino acids), glycosidic bond (sugars), phosphodiester bond (nucleotides), ester bond (fats) |
| Protein structure | Primary: amino acid sequence; secondary: α-helix (right-handed); quaternary example: haemoglobin (2α + 2β) |
| Starch vs cellulose | Starch forms helices that hold iodine (blue colour); cellulose has no such helices, so gives no colour with iodine |
| Inulin and chitin | Inulin: polymer of fructose; chitin: complex polysaccharide in arthropod exoskeletons |
| Fatty acids | Palmitic acid has 16 carbons including the carboxyl carbon; arachidonic acid has 20 |
| Nucleotide | Nitrogen base + pentose sugar + phosphate; purines: adenine, guanine; pyrimidines: cytosine, thymine, uracil |
| B-DNA | Right-handed double helix; A=T (two hydrogen bonds), G≡C (three); 10 base pairs per turn, pitch 3.4 nm |
| Enzyme classes | Oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases |
| Competitive inhibition | Malonate inhibits succinic dehydrogenase |
| Cofactors | Prosthetic group: haem in peroxidase and catalase; coenzyme: NAD and NADP contain niacin; metal ion: zinc for carboxypeptidase |
| Secondary metabolites | Alkaloids (morphine, codeine), pigments (carotenoids, anthocyanins), toxins (abrin, ricin), lectins (concanavalin A), drugs (vinblastin, curcumin), rubber and gums |
What the app covers in this chapter
579 questions in total, each with a detailed explanation.
| What are Biomolecules | 40 |
| Primary and Secondary Metabolites | 59 |
| Biomacromolecules | 60 |
| Proteins | 40 |
| Carbohydrates | 39 |
| Lipids | 39 |
| Nucleic Acids | 42 |
| Enzymes | 40 |
| Mixed practice and chapter tests | 220 |
Questions students ask
Is Biomolecules important for NEET?
Yes. It is a concept-heavy Class 11 chapter whose ideas — protein structure, DNA pairing and enzyme action — are used again in genetics and physiology. Questions are direct and NCERT-based.
Which topics should I revise first?
Start with the bonds and the four levels of protein structure, then polysaccharides and the structure of DNA, and finish with enzyme classes, inhibition and cofactors (use the table on this page).
How many questions from this chapter are on RankUp?
The RankUp app has 579 questions on Biomolecules, including 57 ELITE questions written for students aiming at AIR under 50. Every question has a detailed explanation.
Can I download these questions as a PDF?
Yes. The free PDF on this page has all 24 questions with the answer key and explanations. No signup is needed.
