Biomolecules is a Class 11 Botany chapter in the NEET (UG) syllabus. NEET720 has 436 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.
69
easy
296
medium
71
hard
Topics covered
Chemical Analysis and Micromolecules · Macromolecules · Enzymes · Nucleic Acids in Detail · Biomacromolecules · Biomolecules general · Biomolecules - carbohydrates · Biomolecules - lipids · Biomolecules - overview · Carbohydrates classification · Enzyme kinetics · Enzyme inhibition · Enzyme cofactors · Protein denaturation · Biomolecule composition · Protein classification · Lipids classification · Macromolecules vs micromolecules · Nucleic acid strand orientation · Chargaff's rule · RNA types · Structural role of biomolecules in plants · Protein function diversity · Metabolic pathways · Biomolecules · Polysaccharides · Protein structure · Proteins · Nucleic acids · Lipids · Secondary metabolites · Enzymes and metabolism · Proteins and enzymes · Nucleic acids and proteins · Polysaccharides and storage physiology · Proteins and metabolism · Lipids and membranes · Metabolites · Amino acids · Carbohydrates
8 free Biomolecules practice questions with answers
Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.
Question 1 · medium · Chemical Analysis and Micromolecules
When a living tissue is ground in trichloroacetic acid (TCA) and filtered, the filtrate obtained is called the acid-soluble pool. Which of the following is a correct component of this pool?
- A.Amino acids and other small organic molecules
- B.Cellulose microfibrils of the cell wall
- C.Intact ribosomal RNA molecules
- D.Chloroplast thylakoid proteins
Show answer and explanation
Answer: A. Amino acids and other small organic molecules
Grinding tissue in TCA and filtering separates small, acid-soluble micromolecules (amino acids, sugars, nucleotides) in the filtrate from insoluble macromolecules retained on the filter.
In the classical chemical analysis of a living tissue, the tissue is crushed in trichloroacetic acid, a strong precipitating agent. Filtration yields a filtrate (acid-soluble pool) containing small molecules like free amino acids, simple sugars, and nucleotides, and a retentate (acid-insoluble fraction) containing macromolecules such as proteins, polysaccharides, and nucleic acids. Option A correctly identifies filtrate contents. B, C, and D describe macromolecules that remain in the retentate, not the filtrate.
Common mistake: Assuming any dissolved-looking substance belongs to the filtrate, ignoring molecular size as the actual sorting criterion.
Key point: TCA filtrate = micromolecules (amino acids, sugars, nucleotides); retentate = macromolecules (proteins, polysaccharides, nucleic acids).
Question 2 · easy · Chemical Analysis and Micromolecules
On complete combustion, living tissue leaves behind ash and releases gases. The bulk elemental composition of the 'living state' (C, H, O, N predominating) differs strikingly from that of:
- A.Other living organisms of the same kingdom
- B.The earth's inanimate crust
- C.Plant cell wall polysaccharides
- D.Other biomolecules within the same cell
Show answer and explanation
Answer: B. The earth's inanimate crust
On combustion, living tissue is largely C, H, O, N — proportions that are strikingly different from the relative abundance of these elements in the earth's crust.
Elemental analysis of living tissue on combustion shows it is composed mostly of carbon, hydrogen, oxygen and nitrogen, with lesser amounts of calcium, phosphorus, and other elements left as ash. This proportion of elements in the 'living state' is distinct from the proportion of the same elements found in inanimate matter such as earth's crust. B, C, D misdirect the comparison to living/biomolecular contexts instead of the living-vs-nonliving crust comparison the NCERT text draws.
Common mistake: Confusing the crust comparison with a comparison among biomolecules or organisms.
Key point: Living matter's elemental proportions (C, H, O, N-rich) differ markedly from earth's crust composition.
Question 3 · medium · Chemical Analysis and Micromolecules
A generalised amino acid has a central carbon atom bonded to four different groups. Which of the following correctly lists all four?
- A.Amino group, phosphate group, hydrogen, and a variable R group
- B.Carboxyl group, hydrogen, sugar, and a variable R group
- C.Amino group, carboxyl group, hydrogen, and a variable R group
- D.Amino group, carboxyl group, hydroxyl group, and a variable R group
Show answer and explanation
Answer: C. Amino group, carboxyl group, hydrogen, and a variable R group
The alpha carbon of an amino acid carries an amino group, a carboxyl group, a hydrogen atom, and a variable R (side chain) group.
All 20 standard amino acids share the same basic skeleton: a central (alpha) carbon bonded to an amino (-NH2) group, a carboxyl (-COOH) group, a single hydrogen atom, and a fourth position occupied by a variable R group that determines the amino acid's identity and chemical nature. B wrongly substitutes a phosphate group (a nucleotide feature). C wrongly adds a hydroxyl group in place of hydrogen. D wrongly attaches a sugar (a nucleoside feature). Only A gives the correct four substituents.
Common mistake: Mixing amino acid structural components with those of nucleotides/nucleosides (phosphate, sugar).
Key point: Amino acid = central C + NH2 + COOH + H + variable R group; only R distinguishes the 20 amino acids.
Question 4 · medium · Chemical Analysis and Micromolecules
The 20 different amino acids found in proteins are distinguished from one another chiefly on the basis of:
- A.The presence or absence of the amino group
- B.The number of carboxyl groups present
- C.The type of peptide bond each forms
- D.The nature of the R (side chain) group attached to the alpha carbon
Show answer and explanation
Answer: D. The nature of the R (side chain) group attached to the alpha carbon
All amino acids share amino, carboxyl, and hydrogen groups on the alpha carbon; only the variable R group differs, giving each amino acid its unique identity and classification (acidic, basic, neutral, polar, nonpolar).
Because the amino group, carboxyl group, and hydrogen are constant across all 20 standard amino acids, it is the R group that varies in size, charge, and polarity, and this variation is used to classify amino acids as acidic, basic, or neutral, and as polar or nonpolar. B, C, D each propose an invariant feature as if it were variable, which is biologically incorrect.
Common mistake: Treating constant structural features (amino/carboxyl groups) as the variable, distinguishing feature.
Key point: R group identity determines amino acid classification (acidic/basic/neutral; polar/nonpolar).
Question 5 · easy · Chemical Analysis and Micromolecules
Glucose, fructose, and galactose are all examples of:
- A.Disaccharides
- B.Monosaccharides
- C.Polysaccharides
- D.Amino sugars
Show answer and explanation
Answer: B. Monosaccharides
Glucose, fructose, and galactose are simple, water-soluble, sweet-tasting sugars that cannot be hydrolysed further — the defining features of monosaccharides.
Monosaccharides are the simplest carbohydrates, consisting of a single sugar unit; they are water-soluble and typically sweet. Glucose, fructose, and galactose are classic NCERT examples. Disaccharides (B) form when two monosaccharides join via a glycosidic bond (e.g., sucrose, maltose, lactose), and polysaccharides (C) are long chains of many monosaccharide units (e.g., starch, cellulose). D is a distractor category not relevant here.
Common mistake: Mixing up monosaccharides with disaccharides formed from them.
Key point: Glucose, fructose, galactose = monosaccharides; simplest, single-unit, water-soluble sugars.
Question 6 · medium · Chemical Analysis and Micromolecules
A fatty acid is described as 'unsaturated'. This means the fatty acid:
- A.Has an unusually long hydrocarbon chain compared to saturated fatty acids
- B.Lacks a carboxyl group at one end of the molecule
- C.Is esterified with three glycerol molecules
- D.Contains one or more carbon-carbon double bonds in its hydrocarbon chain
Show answer and explanation
Answer: D. Contains one or more carbon-carbon double bonds in its hydrocarbon chain
Saturated fatty acids have no double bonds between carbon atoms in the chain, while unsaturated fatty acids have one or more double bonds.
Fatty acids consist of a long hydrocarbon chain ending in a carboxyl group; the chain length is variable and independent of saturation status. The key distinguishing feature between saturated and unsaturated fatty acids is the presence (unsaturated) or absence (saturated) of carbon-carbon double bonds. B wrongly ties chain length to unsaturation. C is false since all fatty acids retain a carboxyl group. D describes glyceride formation, a separate concept from fatty acid saturation itself.
Common mistake: Assuming chain length determines saturation rather than presence of double bonds.
Key point: Unsaturated fatty acid = has C=C double bond(s); saturation status is independent of chain length.
Question 7 · hard · Chemical Analysis and Micromolecules
Statement I: Glycerides are formed when fatty acids are esterified with glycerol. Statement II: Fats and oils, both being triglycerides, always differ from each other in their melting point. In light of the above statements, choose the correct answer.
- A.Both Statement I and Statement II are correct
- B.Statement I is correct but Statement II is incorrect
- C.Statement I is incorrect but Statement II is correct
- D.Both Statement I and Statement II are incorrect
Show answer and explanation
Answer: A. Both Statement I and Statement II are correct
Glycerides form by esterification of glycerol with fatty acids; fats and oils are triglycerides that differ from one another based on melting point (fats are solid, oils are liquid at room temperature).
Statement I is correct: a glyceride results from esterification of one, two, or three fatty acid molecules with glycerol (mono-, di-, or triglyceride). Statement II is correct: among triglycerides, those called 'fats' are solid at room temperature (higher melting point, often more saturated fatty acids) while those called 'oils' are liquid at room temperature (lower melting point, often more unsaturated fatty acids) — this melting point difference is precisely what distinguishes the two categories. Both statements align with NCERT content, making A the correct choice.
Common mistake: Not recognising melting point as the defining practical distinction between fats and oils.
Key point: Fats vs oils = triglycerides differing in melting point (fats solid, oils liquid at room temperature).
Question 8 · medium · Chemical Analysis and Micromolecules
Lecithin, an important phospholipid, is chiefly significant in biology because phospholipids of this type are:
- A.The primary storage form of genetic information
- B.Simple sugars used for immediate energy release
- C.Structural components of cell membranes
- D.Enzymes that catalyse hydrolysis of proteins
Show answer and explanation
Answer: C. Structural components of cell membranes
Phospholipids such as lecithin are amphipathic molecules containing phosphorus, and they are key structural components of cell membranes.
Phospholipids contain a phosphorus-containing group in addition to fatty acid chains and glycerol, giving them both hydrophobic and hydrophilic regions. This amphipathic nature makes them the fundamental structural building block of biological membranes. Lecithin is a well-known NCERT example. B wrongly assigns a genetic-information role (that's DNA/RNA, which also has phosphate groups, but is not a phospholipid). C and D wrongly assign enzymatic or simple-sugar-energy roles unrelated to phospholipid function.
Common mistake: Confusing phosphorus-containing phospholipids with phosphorus-containing nucleic acids in terms of function.
Key point: Phospholipids (e.g., lecithin) contain phosphorus and are structural components of cell membranes.
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Questions about Biomolecules for NEET
How many NEET questions does NEET720 have on Biomolecules?＋
NEET720 has 436 reviewed practice questions on Biomolecules (Botany): 69 easy, 296 medium and 71 hard. 8 of them are free on this page with full explanations; the rest are available in the app.
Is Biomolecules a Class 11 or Class 12 chapter for NEET?＋
Biomolecules is a Class 11 Botany chapter in the NEET (UG) syllabus. Read the NCERT chapter first, then practise chapter-wise MCQs and previous-year questions.
How should I practise Biomolecules for NEET?＋
Attempt the questions below without looking at the options for more than a few seconds, mark your answer, then read the explanation even when you were right. Record every mistake and revisit it after a gap. On NEET720 this happens automatically: wrong answers go to your Mistake Book and are scheduled for spaced revision.
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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (436 active practice questions in this chapter today).