313_Chemistry_Eng_Lesson29.pdf). Content covers sections 29.1–29.7.Living organisms are built and maintained by complex organic biomolecules: carbohydrates, proteins, lipids, nucleic acids, enzymes, hormones and vitamins. This lesson covers their classification, key structural features and biological roles — high-yield for boards and foundation for biochemistry.
Produced in plants by photosynthesis. Chemically: polyhydroxy aldehydes or ketones, or substances that yield them on hydrolysis. Sweet monosaccharides/disaccharides are sugars; table sugar is sucrose.
Classification by hydrolysis:
D/L configuration: related to glyceraldehyde. If the lowest asymmetric carbon matches D-(+)-glyceraldehyde (–OH on the right in Fischer projection), the sugar is D-; otherwise L-. Natural glucose is D-glucose.
Important monos: D-glucose (aldohexose, most abundant organic compound); D-fructose (ketohexose, fruit/honey); D-ribose (RNA); 2-deoxy-D-ribose (DNA, no OH at C-2).
In nature, monosaccharides exist mainly as cyclic hemiacetals. Glucose forms a six-membered ring; α and β forms differ only at C-1 — these are anomers. Ribose forms a five-membered ring (α/β).
Disaccharides: joined by a glycoside linkage (loss of water between OH groups). Maltose = two α-glucose; sucrose = glucose + fructose; lactose (milk sugar) = glucose + galactose.
Polysaccharides: starch (plant storage) = amylose (linear α-D-glucose, water-soluble fraction) + amylopectin (branched, insoluble). Cellulose (wood, plant walls) = long chains of β-D-glucose — humans lack enzymes to digest it. Glycogen = animal storage polymer of α-D-glucose, more branched than amylopectin.
Biological roles: energy storage (starch/glycogen); structure (cellulose); ribose/deoxyribose in nucleic acids; glycoproteins and glycolipids for recognition.
Most abundant macromolecules in cells; name from Greek proteios (“of prime importance”). Polymers of α-amino acids. Diet sources: pulses, eggs, meat, milk.
Simple proteins hydrolyse to amino acids only. Fibrous: insoluble, thread-like (collagen, elastin, keratin). Globular: folded spheres, often soluble (egg albumin, serum globulin, haemoglobin).
Conjugated proteins also yield a non-amino prosthetic group: nucleo-, glyco-, chromo-, lipo-, metallo-, phosphoproteins.
By function: transport (Hb, lipoproteins); storage (casein, ovalbumin); structural (keratin, collagen); defence (antibodies); enzymes (pepsin, trypsin); regulatory (insulin).
α-Amino acids: H₂N–CH(R)–COOH. About 20 in proteins; all L-configuration. ~10 are essential (must come from diet).
Peptide bond: –COOH of one AA + –NH₂ of another → amide –CO–NH– + H₂O. Dipeptide, tripeptide… polypeptides; proteins are large polypeptides (insulin has 51 AA but is called a protein). Write sequences with N-terminal (free NH₂) on the left and C-terminal (free COOH) on the right.
Structural levels:
Denaturation: heat or pH change breaks H-bonds; helices uncoil, globules unfold — curdling of milk (lactic acid), cooking egg white. Some proteins (skin, nails, stomach lining) resist denaturation.
Roles: cell structure; enzymes; immunoglobulins; hormones (insulin); growth/repair; fibrinogen (clotting); haemoglobin transports O₂.
From Greek lipos (fat). Cell constituents insoluble in water, soluble in low-polarity solvents (ether, chloroform, benzene).
Simple lipids: esters → fatty acids + alcohol on hydrolysis. Fats, oils, waxes.
Compound lipids: also phosphoric acid, sugars or proteins (phospholipids, glycolipids).
Derived lipids: metabolic products such as steroids and fat-soluble vitamins.
Triglycerides: glycerol esterified with three long-chain fatty acids (often C₁₂–C₂₆). Hydrolysis → glycerol + 3 fatty acids. Fat = solid/semisolid at room temperature; oil = liquid. Saturated chains raise melting point (fats); unsaturation lowers it (oils). Catalytic hydrogenation saturates double bonds — oil → fat (vanaspati ghee). Body stores excess carbohydrate energy as fat; plant oils often in seeds.
Waxes: esters of fatty acids with long monohydric alcohols (C₂₆–C₃₄); protective coatings (beeswax: myricyl palmitate). Not the same as paraffin wax (hydrocarbons).
Phospholipids: membrane building blocks. Steroids: characteristic ring system; cholesterol widely distributed; backbone of many hormones. Fat-soluble vitamins A, D, E, K are derived lipids.
Importance: energy store; aid absorption of ADEK; insulation; membranes; steroid signalling; some enzymes need lipids.
Chromosomes carry heredity; chemically they are nucleic acids — acidic polymers from the cell nucleus. Two types: DNA and RNA.
Polymers of nucleotides. Each nucleotide = nitrogenous base + pentose sugar + phosphoric acid. Chain: sugar–phosphate backbone with bases as side groups.
DNA: sugar = 2-deoxyribose; bases adenine (A), guanine (G), cytosine (C), thymine (T). Double helix (Watson & Crick, 1953): two complementary strands held by H-bonds — A pairs with T, G with C. Sequence of bases = primary structure; double helix = secondary structure.
RNA: sugar = ribose; bases A, G, C and uracil (U) instead of T. Usually single-stranded (may fold). Types: mRNA (message), rRNA (ribosome), tRNA (amino-acid carrier).
Replication: strands unwind; each templates a new complementary strand → two identical double helices (each with one old + one new strand).
Protein synthesis: DNA code → mRNA → cytoplasm; tRNA brings amino acids; peptide bonds form. DNA stores the code; RNA executes synthesis.
Biochemical catalysts that allow complex reactions at body temperature (~310 K), e.g. digestion. Almost all are globular proteins. Named with ending -ase (maltase hydrolyses maltose; esterase acts on esters).
Mechanism: lower activation energy. Lock-and-key: substrate binds active site → enzyme–substrate complex → products + free enzyme. Highly specific; needed in tiny amounts; work in dilute aqueous solution at moderate T and specific pH. Many need coenzymes (non-protein partners, e.g. NAD for dehydrogenases). Many vitamins act as coenzyme precursors.
Chemical messengers from endocrine glands via blood to target tissues.
Steroid hormones: sex hormones (androgens: testosterone; estrogens: estradiol; progesterone for pregnancy) and adrenocortical hormones (aldosterone — Na⁺/K⁺ balance; hydrocortisone — glucose metabolism, inflammation).
Peptide hormones: oxytocin (uterine contraction in childbirth); vasopressin (blood pressure); insulin (pancreas — glucose metabolism; deficiency → diabetes mellitus).
Small organic molecules required in the diet in trace amounts for growth and metabolism. Many function as coenzymes.
Water-soluble: vitamin C (ascorbic acid — bleeding gums); B₁ thiamin (fatigue); B₂ riboflavin (cracked lips); B₆ (anemia); niacin (dermatitis, dementia); folic acid; B₁₂ (anemia, neuro issues); pantothenic acid; biotin.
Fat-soluble: A (night blindness, dry skin); D (rickets, osteomalacia); E (RBC hemolysis); K (bleeding, delayed clotting).
Remember: fat-soluble ADEK need dietary fat for absorption; water-soluble excess is more easily excreted.
High-yield: carb classification and glycoside link; α vs β polymers; peptide bond and 1°–4° protein structure; denaturation; fat vs oil; nucleotide parts; DNA/RNA differences and base pairing; enzyme lock-and-key; insulin and diabetes; vitamin deficiency table (especially A, C, D, K, B₁₂).
Links L28 (amino groups, peptides) and L27 (carbonyls in sugars). Next module topic in the course list: soaps, detergents and polymers (L31). Practice short definitions and comparison tables — they score reliably.
Most exam-important points from this chapter:
Polyhydroxy carbonyls. Mono/di/poly. Glycoside link. α-starch/glycogen · β-cellulose. D/L from glyceraldehyde.
α-AA · peptide bond · 1°–4° structure. Essential AA in diet. Fibrous/globular/conjugated. Denaturation by heat/pH.
Water-insoluble. Triglycerides: fat solid, oil liquid. Hydrogenation. Phospholipids, steroids, ADEK.
Nucleotide units. DNA: deoxyribose, T, double helix, A–T/G–C. RNA: ribose, U, protein synthesis.
Enzymes: protein, specific, lock-key, mild conditions. Vitamins: water vs fat soluble; match deficiencies.
Extracted from NIOS Chemistry (313) board exam papers in your PDF. Chapter L29 — Biomolecules only. Use Model Answer for marking points; Explanation for concept clarity.
5 question(s) · Sources: 313/MAY/205A, 313/MAY/205B, 313/MAY/205C, 313/TUS/105A
PYQ1. Write True (T) for correct statement and False (F) for incorrect statement : Phospholipids are constituents of the cell membrane. The structure of protein molecule is not changed by changing its temperature. ghr
Model Answer
Answer using key concepts from L29 (definitions, equations, and one example where useful). Stay within the suggested word range for a 2-mark NIOS question.
Explanation
Cross-check with L29 notes. Structure: definition/law → working → conclusion. Partial marks for correct equations even if explanation is short.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205A · Q27 · 2 mark(s) · L29.
PYQ2. Write True (T) for correct statement and False (F) for incorrect statement : Phospholipids are constituents of the cell membrane. The structure of protein molecule is not changed by changing its temperature. ghr
Model Answer
Answer using key concepts from L29 (definitions, equations, and one example where useful). Stay within the suggested word range for a 2-mark NIOS question.
Explanation
Cross-check with L29 notes. Structure: definition/law → working → conclusion. Partial marks for correct equations even if explanation is short.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205B · Q18 · 2 mark(s) · L29.
PYQ3. Write True (T) for correct statement and False (F) for incorrect statement : Phospholipids are constituents of the cell membrane. The structure of protein molecule is not changed by changing its temperature. ghr
Model Answer
Answer using key concepts from L29 (definitions, equations, and one example where useful). Stay within the suggested word range for a 2-mark NIOS question.
Explanation
Cross-check with L29 notes. Structure: definition/law → working → conclusion. Partial marks for correct equations even if explanation is short.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/MAY/205C · Q20 · 2 mark(s) · L29.
PYQ4. Chemically enzymes are — (A) polysaccharides (B) polypeptides (C) polynucleotides (D) globular proteins amgm¶{
Model Answer
Model approach (select the best option):
Eliminate options that contradict definitions/equations from the chapter notes. NIOS awards full mark for the single correct choice.
Explanation
This MCQ belongs to L29. Recall the core definition or formula from notes, then match it to one option. Paper: 313/TUS/105A · Q14.
Tip: For numerical MCQs, write the formula first, substitute values, then pick the option.
PYQ5. Read the passage given below and answer the following questions (out of four attempt any two) : Hormones are chemical messengers which are secreted by endocrine glands. They are carried through the blood stream to the target tissues. Vitamins are small organic molecules which are taken in diet and these are required in trace amounts for proper-growth. Name a female sex hormone and state its function. Which disease is caused by the deficiency of insulin in humans? Which gland secretes it? Which water-soluble vitamin’s deficiency causes a disease with symptoms of (i) cracked lips, scaly skin and (ii) anaemia, irritability? Name any two vitamins which are fat-soluble.
Model Answer
Answer using key concepts from L29 (definitions, equations, and one example where useful). Stay within the suggested word range for a 2-mark NIOS question.
Explanation
Cross-check with L29 notes. Structure: definition/law → working → conclusion. Partial marks for correct equations even if explanation is short.
How to write for NIOS: Use 30–50 words (VSA) or short objective. Open with definition/equation, then reason, end with conclusion. Paper 313/TUS/105A · Q27 · 2 mark(s) · L29.
Six problems spanning this chapter’s NIOS syllabus. Every question is built from the notes and formula sheet: solve with equations first, then read the formal textbook-style write-up, the easy explanation, and the topic in depth (formulas, meaning, exam tips). If the question says draw, a labelled pencil sketch is provided. Explanations open by default.
Define monosaccharide and give two examples.
Final answer: Glucose, fructose
Carbohydrates are polyhydroxy aldehydes/ketones or derivatives.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Single sugar units—building blocks of bigger carbs.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Disaccharides hydrolyse to two monosaccharides.
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Is glucose an aldose or ketose? How many carbons?
Final answer: Aldohexose
Open chain has aldehyde; cyclic hemiacetal forms in solution.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Six-carbon sugar with aldehyde end in open form.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
α/β anomers at C1 in rings.
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
What is a peptide bond?
Final answer: –CO–NH– between amino acids
Proteins are polymers of α-amino acids.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Amino acids join by condensation—water leaves, peptide forms.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Primary structure is sequence of amino acids.
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
State two features of enzymes as biological catalysts.
Final answer: Specific; protein catalysts
Enzymes accelerate reactions under mild conditions.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Nature’s catalysts—pick one substrate and work fast at body temperature.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Denatured by heat/extremes of pH.
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Name the sugar in DNA and the four bases.
Final answer: Deoxyribose; A T G C
Nucleotides: base + sugar + phosphate.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
DNA uses deoxyribose and thymine; RNA uses ribose and uracil.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Base pairing A–T, G–C in double helix.
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.
Classify vitamins as water- or fat-soluble with one example each.
Final answer: Water: B/C; fat: A/D/E/K
Deficiency diseases linked to specific vitamins.
Working formulas: (see solution steps). State the definition or law first (NIOS style), use SI units, and box the final numerical answer with unit.
Some vitamins wash out in urine; others store in fat.
Read once for the idea, once for the numbers. Write the formula, substitute, then simplify. Check whether you used moles, grams, or litres correctly.
Vitamin C deficiency → scurvy (classic).
Linked to chapter notes (L29). Remember: (see solution steps). Most exam errors are unit mix-ups (g vs mol, mL vs L) or wrong mole ratios from the equation.
Write (see solution steps) before substituting. Keep three significant figures until the end when data allow.