Class 12 Chemistry Chapter 10 Biomolecules is the one chapter where organic chemistry stops being about reactions on paper and starts mapping directly onto living tissue, with the 2026-27 NCERT keeping every sub-system from carbohydrates to nucleic acids fully examinable. This Collegedunia formula sheet collates every structural rule, reagent test, base-pairing fact, and vitamin-deficiency pair on a printable revision page aligned with the new edition.
- CBSE Weightage: 3 to 5 marks
- JEE Main Weightage: 1 to 2 percent (1 to 2 questions per paper)
- NEET Weightage: 1 to 2 questions per year
The compact sheet that follows lists every structural fact, reagent test, base-pair rule, and vitamin-deficiency pair with its NCERT section reference.
This formula sheet is curated by Collegedunia subject experts, mapped to the 2026-27 new NCERT edition, and refined against the last five years of CBSE Board, JEE Main, and NEET papers.
Also Check:
- Biomolecules Class 12 Chemistry Notes
- Biomolecules Class 12 Chemistry NCERT Solutions
- CBSE Class 12 Chemistry Syllabus 2026-27
Why Biomolecules Matters in 12th Chemistry and Entrance Exams
Biomolecules is the chapter that pulls every previous Organic block together and feeds it into the Biology / Biotechnology paper line. Carbohydrate chemistry brings back aldehyde and ketone testing from Chapter 8; amino-acid zwitter ions reuse the acid-base logic from Chapter 9; nucleic acid backbones recycle the ester linkage from Chapter 7. CBSE has set at least one 2-mark question on DNA / RNA differences in 4 of the last 5 board papers, and NEET has tested vitamin-deficiency pairs every year since 2021. Students who lock in the glycosidic linkage, peptide bond, phosphodiester linkage trio plus the fat-soluble ADEK rule pick up 3 to 4 nearly-guaranteed marks across CBSE, JEE Main, and NEET.
Biomolecules Video Walkthrough
Source: Magnet Brains on YouTube
How will Collegedunia's Biomolecules Formula Sheet Help You?
The sheet is built for a 20 to 25 minute final-night revision pass before a Chemistry paper.
- 2026-27 NCERT Alignment: Every structural fact, reagent test, and base-pairing rule matches the current syllabus print of Sections 10.1 to 10.6.
- One-Page Printability: The master reference table fits on a single A4 landscape sheet.
- Sub-System Tagging: Each fact is tagged Carbohydrate, Amino acid, Protein, Enzyme, Vitamin, Nucleic acid, or Hormone, so you can pull the right answer for any 2-mark slot.
- Expert Verification: Cross-checked against NCERT Sections 10.1 to 10.6 and the last five JEE Main and NEET papers.
Biomolecules Symbol and Notation Glossary for 12th Chemistry
The glossary below locks in every notation used in the master table. More than half of the 1-mark CBSE slips on Chapter 10 come from confusing ribose with deoxyribose, or putting thymine inside an RNA strand.
| Symbol | Meaning | Typical Unit / Note |
|---|---|---|
| Cx(H2O)y | Empirical carbohydrate formula | Memory aid only; rhamnose breaks it |
| D, L | Relative configuration (vs D-glyceraldehyde) | Italic capitals; geometry only |
| (+), (−) | Dextro- / laevo-rotatory | Measured optical rotation; independent of D / L |
| α, β | Anomeric configurations | α-OH below ring (Haworth); β-OH above ring |
| R−CH(NH2)−COOH | α-amino acid general formula | 20 natural; only α in proteins |
| +H3N−CHR−COO− | Zwitter ion | Net charge 0; amphoteric in water |
| −CO−NH− | Peptide / amide linkage | Between −COOH and −NH2 of next AA |
| 1°, 2°, 3°, 4° | Four levels of protein structure | Sequence; helix/sheet; 3-D fold; sub-unit assembly |
| Ea | Activation energy | Sucrose hydrolysis: 6.22 (H+) → 2.15 (sucrase) kJ mol−1 |
| A, T, G, C, U | Nitrogenous bases | A/G purines; C/T/U pyrimidines; U only in RNA, T only in DNA |
| 3′, 5′ | Sugar-ring carbons (nucleic acid) | Phosphodiester linkage: 3′ of one sugar to 5′ of next |
| ADEK | Fat-soluble vitamins | A, D, E, K; stored in liver / adipose |
Biomolecules All Important Formulae and Reactions for Class 12 Chemistry
The canonical master table below lists every structural rule, reagent test, glycosidic / peptide / phosphodiester linkage, and quantitative trend in NCERT Chapter 10, with conditions, section reference, and the typical exam-use cue. All entries below are retained in the 2026-27 syllabus.
| Concept / Reaction | Formula / Structure | Conditions / Notes | NCERT Ref | Common Use |
|---|---|---|---|---|
| Carbohydrate (modern definition) | Polyhydroxy aldehyde / ketone, optically active | Empirical Cx(H2O)y is only a memory aid | 10.1 | Rhamnose C6H12O5 is a carbohydrate but breaks the empirical form |
| Monosaccharide (hexose) | C6H12O6 | Cannot be hydrolysed further | 10.1 | Glucose, fructose, galactose |
| Disaccharide (sucrose) | C12H22O11 | 2 monosaccharide units; glycosidic linkage | 10.1.3 | Sucrose, maltose, lactose |
| Polysaccharide | (C6H10O5)n | Many monosaccharide units; non-sweet | 10.1.4 | Starch, cellulose, glycogen |
| Glucose (aldohexose) | CHO-(CHOH)4-CH2OH | D-(+); 4 chiral C; pyranose ring | 10.1.2 | Open-chain Fischer; six chemical evidences |
| Glucose preparation (commercial) | (C6H10O5)n + nH2O H2SO4, 393 K, 2-3 atm nC6H12O6 | Starch + dil. H2SO4 | 10.1.2.1 | Industrial route; pure glucose only |
| Glucose + HI, Δ | Glucose HI, Δ n-hexane | Prolonged heating | 10.1.2.1 | Proves straight 6-C chain |
| Glucose + Br2 water (mild) | Glucose Br2/H2O Gluconic acid | Mild oxidation of −CHO | 10.1.2.1 | Mono-COOH; proves aldehydic group |
| Glucose + HNO3 (strong) | Glucose HNO3 Saccharic acid | Strong oxidation of both ends | 10.1.2.1 | Di-COOH; proves terminal −CH2OH |
| Glucose + (CH3CO)2O | Glucose (CH3CO)2O Glucose pentaacetate | Acetic anhydride | 10.1.2.1 | Proves five −OH groups |
| Glucose + NH2OH / HCN | Glucose NH2OH oxime; HCN cyanohydrin | Reveal C=O | 10.1.2.1 | Proves the −CHO group |
| Cyclic hemiacetal (glucose) | −OH at C5 attacks −CHO at C1 → 6-membered pyranose ring | α (m.p. 419 K), β (m.p. 423 K) | 10.1.2.1 | New chiral C1 = anomeric C; α / β anomers; mutarotation |
| Fructose (ketohexose) | CH2OH-CO-(CHOH)3-CH2OH | D-(−); furanose ring | 10.1.2.2 | −OH at C5 attacks >C=O at C2 → 5-membered ring |
| Glycosidic linkage | Sugar1-OH + HO-Sugar2 → Sugar1-O-Sugar2 + H2O | Loss of H2O; H+ or enzyme reverses | 10.1.3 | Ether-like C−O−C bridge |
| Sucrose hydrolysis (invert sugar) | C12H22O11 + H2O H+ or invertase D-(+)-glu + D-(-)-fru | Equimolar; [α] flips +66.5° → −39.9° | 10.1.3 | α-D-glu C1 → β-D-fru C2 ; non-reducing |
| Maltose | 2 α-D-glucose units; C1(I)–C4(II) linkage | One free hemiacetal ⇒ reducing | 10.1.3 | Maltase hydrolysis → 2 glucose |
| Lactose (milk sugar) | β-D-galactose (C1) – β-D-glucose (C4) | Free hemiacetal on glucose ⇒ reducing | 10.1.3 | Lactase hydrolysis → glucose + galactose |
| Starch (amylose + amylopectin) | (C6H10O5)n ; α-D-glucose | Amylose 15-20%, C1–C4 unbranched; amylopectin 80-85%, C1–C4 + C1–C6 branches | 10.1.4 | I2/KI → deep blue |
| Cellulose | β-D-glucose; C1–C4 β-glycosidic | Structural; indigestible to humans | 10.1.4 | Most abundant organic substance; wood, cotton, paper, rayon |
| Glycogen (animal starch) | α-D-glucose; like amylopectin but more highly branched | Stored in liver, muscles, brain | 10.1.4 | Hydrolysed to glucose on demand |
| α-Amino acid general formula | R-CH(NH2)-COOH | R = side chain | 10.2.1 | 20 natural; chiral except glycine (R = H) |
| Acidic / basic / neutral AA | Count side-chain −COOH vs −NH2 | More −COOH = acidic (Asp, Glu); more −NH2 = basic (Lys, Arg, His) | 10.2.1 | Side chain only; not the backbone |
| Essential amino acids (10) | Val, Leu, Ile, Thr, Met, Phe, Trp, Lys, Arg, His | Body cannot synthesise; must come from diet | 10.2.2 | NCERT count = 10 (memorise list) |
| Zwitter ion | R-CH(NH2)-COOH R-CH(+NH3)-COO- | Net charge 0; amphoteric | 10.2.2 | Explains high m.p. + water solubility of AA |
| Peptide bond | H2N-CHR1-COOH + H2N-CHR2-COOH -H2O -CHR1-CO-NH-CHR2- | Amide between −COOH and −NH2 | 10.2.3 | Dipeptide; the boxed −CO−NH− is the peptide bond |
| Polypeptide vs protein | >10 AA = polypeptide; >100 AA or M > 10,000 u = protein | Boundary is not sharp | 10.2.3 | Insulin (51 AA) is still called a protein |
| Four levels of protein structure | 1° sequence → 2° helix/sheet → 3° 3-D fold → 4° sub-unit assembly | 2°: H-bonds between peptide C=O and N−H | 10.2.3 | Haemoglobin = 4 sub-units (4°) |
| Fibrous vs globular | Parallel chains, insoluble (keratin, myosin) vs spherical, soluble (insulin, albumins) | Function follows shape | 10.2.3 | Fibrous = structural; globular = enzymes / transport |
| Denaturation | Heat / pH / urea / heavy metal / organic solvent | 2° and 3° lost; 1° preserved | 10.2.3 | Egg-white coagulation, milk curdling |
| Enzyme (general) | Globular protein; substrate-specific; suffix −ase | Lowers Ea without being consumed | 10.3 | Maltase, sucrase, lactase, zymase, pepsin, trypsin |
| Enzyme Ea drop (NCERT) | Ea (H+) = 6.22 kJ mol-1; Ea (sucrase) = 2.15 kJ mol-1 | Sucrose hydrolysis | 10.3 | Enzyme drops Ea to about one-third |
| Fat-soluble vitamins | A, D, E, K (ADEK) | Stored in liver and adipose tissue | 10.4 | Insoluble in water |
| Water-soluble vitamins | B group + C | Excreted in urine; supplied regularly | 10.4 | Exception: B12 is stored |
| Nucleic acid composition | Pentose sugar + H3PO4 + nitrogen base | Sugars: β-D-ribose (RNA), β-D-2-deoxyribose (DNA) | 10.5 | DNA: A,G,C,T; RNA: A,G,C,U |
| Nucleoside vs nucleotide | Base + sugar (N-glycosidic at C1′) vs Base + sugar + phosphate (ester at C5′) | Nucleotide = phosphate ester of nucleoside | 10.5 | Nucleic acid = polynucleotide |
| Phosphodiester linkage | …-Sugar-C3'O-P(=O)(O-)-C5'O-Sugar-… | 3′ of one to 5′ of next | 10.5 | Sugar-phosphate backbone; bases project sideways |
| Watson-Crick base pairing | A ··· T (2 H-bonds); G ··· C (3 H-bonds) | 1 : 1 ratio in any DNA (Chargaff) | 10.5 | Molecular basis of replication |
| Hormones (chemical classes) | Steroid / polypeptide / amino-acid-derived | Endocrine origin; act at a distance | 10.6 | Estrogens, testosterone (steroid); insulin (polypeptide); thyroxine, epinephrine (AA-derived) |
| Insulin / glucagon | Pancreas; insulin lowers, glucagon raises blood glucose | Insulin: 51 AA, β-cells; glucagon: α-cells | 10.6 | Textbook example of hormonal homeostasis |
| Thyroxine | Iodinated tyrosine derivative (thyroid) | Low ⇒ hypothyroidism (goitre) | 10.6 | Iodised salt prevents I-deficiency goitre |
The single highest-frequency CBSE 1-mark slip on this chapter is the sugar-ring swap: glucose → pyranose (6-ring), fructose → furanose (5-ring). Tag every cyclic-form question with the sugar name first, then choose the ring size.
Quick Carbohydrate Linkage Map (Sucrose, Maltose, Lactose, Starch, Cellulose, Glycogen)
The disaccharide and polysaccharide linkages CBSE / NEET keep testing. Memorise the linkage type and the reducing-sugar status together.
| Sugar | Linkage | Hydrolysis | Reducing? |
|---|---|---|---|
| Sucrose | alpha-D-glu C1 ↔ beta-D-fru C2 (alpha,beta-1,2) | Glucose + fructose (invert sugar; rotation +66.5 to -39.9) | Non-reducing (both anomeric C locked) |
| Maltose | 2 alpha-D-glucose, alpha-1,4 | 2 glucose | Reducing (one free hemiacetal) |
| Lactose | beta-D-galactose C1 ↔ beta-D-glucose C4 (beta-1,4) | Galactose + glucose | Reducing |
| Starch (amylose + amylopectin) | amylose alpha-1,4 linear; amylopectin alpha-1,4 + alpha-1,6 branches | Maltose → glucose (amylase) | Non-reducing |
| Cellulose | beta-D-glucose, beta-1,4 straight chain | Indigestible to humans | Non-reducing |
| Glycogen ("animal starch") | alpha-D-glucose; alpha-1,4 + frequent alpha-1,6 branches | Glucose-1-phosphate (phosphorylase) | Non-reducing |
Anomers, Epimers and Mutarotation - The Stereochemistry of Glucose
- Anomers differ only at the anomeric carbon (C1 in aldoses, C2 in ketoses). Alpha-D-glucose: -OH below the ring at C1; beta-D-glucose: -OH above. Anomerisation goes via the open-chain aldehyde.
- Epimers differ at one non-anomeric chiral carbon. Glucose / galactose are C4 epimers; glucose / mannose are C2 epimers.
- Mutarotation: alpha-D-glucose ([alpha] = +112) equilibrates in water through the open chain to give beta-D-glucose ([alpha] = +19); the equilibrium specific rotation is +52.5 degrees.
- Fructose: ketohexose; cyclises C5-OH attacking C2 to give a 5-membered furanose ring; D-(-), [alpha] = -92.4 degrees. Note that "D" does not predict the sign of rotation.
Nucleoside vs Nucleotide; DNA vs RNA Composition
| Property | DNA | RNA |
|---|---|---|
| Sugar | beta-D-2-deoxyribose (no -OH at C2') | beta-D-ribose (-OH at C2' present) |
| Bases | A, G, C, T | A, G, C, U (uracil replaces thymine) |
| Strand | Right-handed double helix, antiparallel | Single strand; folds back in tRNA, rRNA |
| Base pairs | A ··· T (2 H-bonds); G ··· C (3 H-bonds) | Internal A-U / G-C in hairpin loops |
| Function | Stores hereditary information; replicates | mRNA carries message; tRNA delivers AA; rRNA forms ribosome |
Nucleoside = base + sugar (no phosphate, N-glycosidic linkage at C1'); nucleotide = base + sugar + phosphate (ester at C5'). Nucleotides polymerise to nucleic acids via the 5' to 3' phosphodiester linkage. Purines (double-ring) = A, G; pyrimidines (single-ring) = C, T, U. Mnemonic "PURe As Gold" for purines.
One-Shot Revision Tips for Class 12th Chemistry Biomolecules
- Count the rings, not the carbons, for sugars: 6 atoms in the ring = pyranose (glucose); 5 atoms in the ring = furanose (fructose). Faster than counting C atoms when the Haworth structure is drawn out.
- Anomers differ only at one carbon — the anomeric C (C1 in aldoses, C2 in ketoses). Everything else in the ring is identical between α and β.
- Sucrose is non-reducing because BOTH anomeric −OH groups (C1 of glucose + C2 of fructose) are locked in the glycosidic linkage. Maltose and lactose each keep one free hemiacetal, so they reduce Fehling and Tollens reagents.
- Cellulose is β-1,4; starch and glycogen are α-1,4 — the only structural difference, but it is the reason humans digest starch and cannot digest cellulose.
- Denaturation destroys 2° and 3°, not 1°: the peptide bonds (1° structure) survive boiling, acid, urea, or heavy-metal exposure. That is why a boiled egg-white is still a chain of amino acids, just no longer folded.
- ADEK floats in oil: the four fat-soluble vitamins are A, D, E, K. Everything else is water-soluble. The one exception that is stored anyway is B12.
Biomolecules Quick-Fact Cards for MCQ Recall
The four facts below are the ones JEE Main and NEET rotate as 1-mark MCQs. Memorise them in this exact form.
Vitamins, Sources and Deficiency Reference Table for Biomolecules
The pairs below power most of the 1-mark MCQs on Section 10.4. NEET has asked at least one vitamin-deficiency question every year since 2021.
| Vitamin | Solubility class | Main source | Deficiency disease |
|---|---|---|---|
| A | Fat-soluble | Fish liver oil, carrots, butter, milk | Xerophthalmia, night blindness |
| B1 (thiamine) | Water-soluble | Yeast, milk, cereals | Beri-beri |
| B2 (riboflavin) | Water-soluble | Milk, egg white, liver, kidney | Cheilosis |
| B6 (pyridoxine) | Water-soluble | Yeast, milk, egg yolk, cereals | Convulsions |
| B12 | Water-soluble (but stored) | Meat, fish, egg, curd | Pernicious anaemia |
| C (ascorbic acid) | Water-soluble | Citrus fruits, amla, leafy vegetables | Scurvy, bleeding gums |
| D | Fat-soluble | Sunlight, fish, egg yolk | Rickets, osteomalacia |
| E | Fat-soluble | Wheat germ oil, sunflower oil | RBC fragility, muscular weakness |
| K | Fat-soluble | Green leafy vegetables | Increased blood-clotting time |
Top 3 Most-Asked Biomolecules PYQ Topics in CBSE, JEE and NEET
The three patterns below have repeated most often since 2021. The full year-by-year map sits on the Collegedunia NCERT Solutions page.
| Topic | Frequency (CBSE + JEE + NEET, 2026 to 2021) | Typical mark band |
|---|---|---|
| DNA vs RNA differences (sugar, base, strands) | 11 times | 2 to 3 marks |
| Vitamin-deficiency pairing (A-night blindness, K-clotting, etc.) | 10 times | 1 mark |
| Glucose chemical evidences (Br2/water, HNO3, acetic anhydride) | 8 times | 2 to 3 marks |
Full year-wise PYQ map: Biomolecules Class 12 Chemistry NCERT Solutions
Biomolecules Common-Numerical Pattern Templates for 12th Chemistry
The four problem setups below have dominated CBSE, JEE Main, and NEET papers since 2021.
| Pattern | What the question gives | Formula / Rule to apply | Common trap |
|---|---|---|---|
| Reducing vs non-reducing | Disaccharide name (sucrose, maltose, lactose) — classify | Both anomeric −OH in linkage ⇒ non-reducing (sucrose); one free hemiacetal ⇒ reducing (maltose, lactose) | Saying lactose is non-reducing because it has two sugars |
| Glycosidic linkage type | Sucrose / maltose / lactose / cellulose / starch — name the linkage | Sucrose: α-glu C1 — β-fru C2; maltose: α-1,4; lactose: β-1,4 (gal-glu); starch / glycogen: α-1,4 + α-1,6 branches; cellulose: β-1,4 | Mixing α with β for starch vs cellulose |
| Vitamin-deficiency match | Disease name (scurvy, beri-beri, night blindness, rickets, pernicious anaemia, increased clotting time) | C, B1, A, D, B12, K respectively | Confusing B1 (beri-beri) with B12 (pernicious anaemia) |
| DNA / RNA composition | List of bases / sugars / strand types — identify DNA vs RNA | DNA: deoxyribose + A, G, C, T, double helix; RNA: ribose + A, G, C, U, single strand | Putting thymine in RNA or uracil in DNA |
Biomolecules Weightage Compared Across Class 12 Chemistry Chapters
Typical CBSE marks distribution across the 10 chapters of the 2026-27 NCERT, averaged over the last five board papers. Biomolecules sits in the low-tier, similar to Haloalkanes and Haloarenes — high-yield per page-of-reading because the entire chapter rewards rote-recall of structural pairs and reagent maps.
Related Links:
- Amines Class 12 Chemistry Formula Sheet (Previous Chapter)
- Solutions Class 12 Chemistry Formula Sheet (Chapter 1)
More Biomolecules Chemistry Class 12 Resources
NCERT Formula Sheet for Class 12 Chemistry: All Chapters
Jump to the formula sheet for any other chapter of Class 12 Chemistry below.
| Chapter | Resource |
|---|---|
| Chapter 1 | Solutions Formula Sheet |
| Chapter 2 | Electrochemistry Formula Sheet |
| Chapter 3 | Chemical Kinetics Formula Sheet |
| Chapter 4 | d- and f-Block Elements Formula Sheet |
| Chapter 5 | Coordination Compounds Formula Sheet |
| Chapter 6 | Haloalkanes and Haloarenes Formula Sheet |
| Chapter 7 | Alcohols, Phenols and Ethers Formula Sheet |
| Chapter 8 | Aldehydes, Ketones and Carboxylic Acids Formula Sheet |
| Chapter 9 | Amines Formula Sheet |
Biomolecules Class 12 Chemistry Formula Sheet FAQs
Ques. Where can I download the Biomolecules Class 12 Chemistry Formula Sheet PDF?
Ans. You can download the Biomolecules Class 12 Chemistry Formula Sheet PDF directly from this Collegedunia page. Both the Normal and HD versions are available and free of cost.
Ques. Is this Formula Sheet aligned with the 2026-27 NCERT?
Ans. Yes. This page reflects the current 2026-27 syllabus for Class 12 Chemistry. Biomolecules is fully retained in the new edition with no structural cuts; every concept in Sections 10.1 to 10.6 of the NCERT remains examinable.
Ques. How many pages is the Class 12th Chemistry Biomolecules Formula Sheet PDF?
Ans. The Formula Sheet PDF runs approximately 18 pages and covers the carbohydrate master table, amino-acid and protein structural rules, enzyme activation-energy data, the vitamin-deficiency reference, the DNA-RNA comparison, and the hormone classification.
Ques. What is the difference between glucose and fructose at the structural level?
Ans. Both have the same molecular formula C6H12O6 , but they differ in three structural respects. Glucose is an aldohexose: it carries a −CHO group at C1 and four chiral centres (C2, C3, C4, C5). Fructose is a ketohexose: it carries a >C=O at C2, a primary −OH at C1, and three chiral centres. On cyclisation, the −OH at C5 of glucose attacks the C1 aldehyde to give a six-membered pyranose ring (one O + five C); in fructose the −OH at C5 attacks the C2 keto to give a five-membered furanose ring (one O + four C). Glucose is dextrorotatory ([α]D = +52.5∘) ; fructose is laevorotatory ([α]D = -92.4∘) . The 1 : 1 mixture obtained when sucrose hydrolyses is called invert sugar because the net rotation flips from + to −.
Ques. Why are sucrose, maltose and lactose classified differently on the reducing test?
Ans. A reducing sugar must have at least one free hemiacetal (a C bearing both an −OH and an −OR via the ring oxygen) which can open back to a free −CHO and reduce Fehling or Tollens reagent. Sucrose (α-D-glucose C1 – β-D-fructose C2) uses both anomeric −OH groups (C1 of glucose and C2 of fructose) inside the glycosidic linkage, so neither sugar can open up — sucrose is non-reducing. Maltose (two α-D-glucose units linked C1–C4) and lactose (β-D-galactose C1 – β-D-glucose C4) each leave one anomeric C free, so they retain a hemiacetal and reduce Fehling and Tollens. The same rule explains why all monosaccharides reduce both reagents.
Ques. What exactly happens during the denaturation of a protein, and is it reversible?
Ans. Denaturation is the loss of the secondary and tertiary three-dimensional structure of a protein, triggered by heat, pH change, urea, organic solvents, or heavy-metal salts. The hydrogen bonds that hold the α-helix and the β-pleated sheet, plus the disulphide −S−S− bridges that lock the 3-D fold, are cleaved. The primary structure (the peptide-bond sequence) is preserved because the −CO−NH− bond itself is not broken. The protein loses biological activity (a denatured enzyme cannot catalyse; a denatured hormone cannot signal). Common examples include the coagulation of egg-white on boiling and the curdling of milk by lactic acid from bacteria. In most cases denaturation is irreversible in a laboratory setting; refolding the chain back into its native conformation requires either chaperone proteins or controlled cellular conditions and is rarely complete.
Ques. How does the structure of DNA differ from the structure of RNA?
Ans. DNA and RNA differ at three structural levels. Sugar: DNA contains β-D-2-deoxyribose (no −OH at C2′); RNA contains β-D-ribose (−OH at C2′ retained). Bases: DNA uses adenine, guanine, cytosine, and thymine; RNA uses adenine, guanine, cytosine, and uracil in place of thymine. Strand architecture: DNA is a right-handed double helix with two antiparallel strands held by the Watson-Crick base pairs A···T (two H-bonds) and G···C (three H-bonds), giving Chargaff's 1:1 ratio. RNA is single-stranded and exists in three functional forms (mRNA, rRNA, tRNA) that work together during protein synthesis. DNA stores hereditary information and self-replicates; RNA executes the genetic message, and it does not self-replicate inside cells.
Ques. Which vitamin deficiencies cause scurvy, beri-beri, night blindness, rickets, and increased blood clotting time?
Ans. The five disease-vitamin pairs that NCERT Table 10.3 fixes are: Scurvy → deficiency of Vitamin C (ascorbic acid; sourced from citrus and amla); Beri-beri → deficiency of Vitamin B1 (thiamine); Night blindness / xerophthalmia → deficiency of Vitamin A; Rickets / osteomalacia → deficiency of Vitamin D; Increased blood-clotting time → deficiency of Vitamin K. NCERT exercise 10.19 asks "name the vitamin responsible for the coagulation of blood" and the marking scheme expects only "Vitamin K".
Ques. Why is insulin called a protein when it is only 51 amino acids long?
Ans. The boundary between polypeptide and protein is not a sharp count. NCERT records that compounds with more than 10 amino acid residues are usually called polypeptides, and those with more than 100 residues or a molecular mass above 10,000 u are called proteins. Insulin sits below both of those numerical thresholds (51 residues, M about 5,800 u), but it has a clearly defined three-dimensional fold built from two polypeptide chains held together by disulphide −S−S− bridges, and it performs a well-defined biological function (lowering blood glucose by promoting cellular uptake and storage as glycogen). Because of that well-defined 3-D structure and dedicated function, NCERT and IUPAC convention both classify insulin as a protein hormone, even though by residue count alone it would technically be a polypeptide.
Ques. What is the difference between anomers and epimers and how is mutarotation defined?
Ans. Anomers are stereoisomers of sugars that differ only at the anomeric carbon - C1 in aldoses or C2 in ketoses - which is the new chiral centre created when the open chain cyclises. Alpha- and beta-D-glucopyranose are anomers. Epimers are stereoisomers that differ at one non-anomeric chiral carbon: glucose and galactose are C4 epimers; glucose and mannose are C2 epimers. Mutarotation is the gradual change in specific rotation when a pure anomer of a reducing sugar dissolves in water and equilibrates with the other anomer through the open-chain form. For D-glucose, pure alpha has [α] = +112°, pure beta has [α] = +19°, and the equilibrium mixture has [α] = +52.5°.
Ques. How is haemoglobin an example of quaternary protein structure?
Ans. Haemoglobin is built from four polypeptide subunits - two α chains (141 residues each) and two β chains (146 residues each) - each cradling a heme group with a Fe(II) centre. The four subunits associate through non-covalent interactions and salt bridges; total molecular mass is about 64,500 u. Cooperative O2 binding (positive cooperativity) gives haemoglobin its sigmoidal binding curve, distinguishing it from monomeric myoglobin (a tertiary-only protein). The association of two or more polypeptide chains defines quaternary structure.
Ques. What are purines and pyrimidines and which bases appear in DNA vs RNA?
Ans. Purines are double-ring nitrogen bases - adenine (A) and guanine (G); mnemonic "PURe As Gold". Pyrimidines are single-ring bases - cytosine (C), thymine (T) and uracil (U). DNA contains A, G, C, T; RNA replaces thymine with uracil and so contains A, G, C, U. The Watson-Crick base pairs in DNA are A ··· T (2 H-bonds) and G ··· C (3 H-bonds), each pairing one purine with one pyrimidine.
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