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CBSE Class 12 · Chemistry

Biomolecules

Official NCERT chapter from Chemistry Part I–II (book code lech1). ExamMaster notes are original teaching at CBSE Class 12 depth.

This lesson follows the official chapter “Biomolecules” in Chemistry Part I–II. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 12
  • Medium level
  • 8 concepts

1Carbohydrates

Carbohydrates: sugars and sugar-chains as taught — glucose, sucrose, starch, cellulose as cases. A carbohydrate is a polyhydroxy-carbonyl family (or its chain), not “any sweet”. Reducing versus non-reducing if named.

Table salt labelled a carbohydrate because it is “food” is a miss.

Figure. Carbohydrates split by how far hydrolysis goes: a monosaccharide is already one sugar (glucose), a disaccharide gives two (sucrose → glucose + fructose), a polysaccharide gives many (starch). The tree is the class test, not a drawing of rings.

How it works

  1. Name a sugar or a poly-sugarThe carbohydrate.
  2. Keep glucose / starch / cellulose as casesThe family.
  3. Refuse sweet as the only testA family-look.

2Proteins

Proteins: amino-acid chains with a job as taught. Peptide bond is the link. Protein is name-plus-job; a mute “body-building” slogan is not the heading. One haemoglobin or enzyme mention is enough.

A starch called protein because both are “food” is a miss.

Figure. Two amino acids join by a condensation: the carboxyl of one and the amino of the next make a peptide −CO−NH− and water leaves. A protein is that amide repeated. Side chains R and R' stay on the carbons; they are not the link.

How it works

  1. Name amino-acid chain + a jobThe protein.
  2. Keep the peptide link if taughtThe bond.
  3. Refuse a slogan as the testA chain-job.

3Enzymes

Enzymes: protein-catalysts that speed a named reaction as taught. Active site and a T/pH caution if listed. Enzyme is a speed-and-fit, not a vitamin.

A hormone called an enzyme because both are “chemicals in the body” is a miss.

Figure. An enzyme does not change the reactant or product energy — both curves share those endpoints — so ΔE is the same. It only cuts the peak. The terracotta path is the uncatalysed climb; the sage path is the catalysed one. Neither series is labelled at the shared end, because those labels would land on the same pixel.

How it works

  1. Name protein + speed a reactionThe enzyme.
  2. Keep substrate and site if askedThe fit.
  3. Refuse a vitamin-swapA catalyst.

4Vitamins

Vitamins: organic helpers needed in small amounts as taught, often from food. Fat-soluble versus water-soluble if split. A vitamin is a food-helper, not a hormone (that is a made-here signal).

A hormone-pill labelled vitamin is a miss.

Figure. The split is solubility, not 'importance'. A, D, E and K dissolve in fat and can be stored; B-complex and C dissolve in water and are not banked, so the diet has to bring them again. Roles mark stored versus daily — not good versus bad.

How it works

  1. Name a small-amount food-helperThe vitamin.
  2. Split fat/water only if taughtThe extra.
  3. Refuse a made-here signal as this headingThat is hormone.

5Nucleic Acids

Nucleic acids: DNA and RNA as taught — information-chains of nucleotides. A nucleic acid is a base-sequence story, not a “life juice”. One DNA-double-line mention is enough.

A protein as DNA because both are “in the nucleus-talk” is a miss.

Figure. A nucleotide is three pieces: phosphate, a pentose sugar, and a nitrogenous base. Nucleic acids are those units chained at the sugar–phosphate backbone; the bases are the information, not the spine. No helix is drawn — the vocabulary has no arc.

How it works

  1. Name DNA or RNA and the nucleotide-chainNucleic acid.
  2. Keep information as the jobThe heading.
  3. Refuse a juice-sloganA sequence-word.

6Hormones

Hormones (chemistry size): chemical signals as taught — a named peptide or steroid if listed. Hormone here is a biomolecule-class, not a medical lecture. Stage-names only; no extra private how-to.

A vitamin as a hormone because both are “tiny chemicals” is a miss.

Figure. A hormone is a message, not the gland and not the job. The gland releases it into blood; only a matching target answers. The figure is that three-box path — a still map, not the time course of a pulse.

How it works

  1. Name a blood-signal biomoleculeThe hormone.
  2. Keep one taught type if listedThe extra.
  3. Stay on stage-namesThis class.

7A definition is a test you can run

Biomolecule-word is a test: a sugar-chain, a peptide, an enzyme, a vitamin, DNA/RNA, or a hormone-class. If you only say “life chemical”, you have a heading.

A leaf-sticker is not the test.

Figure. A class name is a test you can run: hydrolyse the sample and read the units. Sugars mean a carbohydrate, amino acids a protein, nucleotides a nucleic acid. The word is not a decoration on the formula.

How it works

  1. Name the familyThe object.
  2. Give the school sentenceThe test.
  3. Then the word has contentThe definition ran.

8Name the given before the unknown

The given is a name (glucose, DNA, a vitamin). The unknown is the family. Copy starch before you treat it as a protein.

Using enzyme-talk on a vitamin is a silent swap.

Figure. Name what the paper already gave — here a hexose formula and a positive Tollen test — before chasing which sugar. Those two facts already say reducing aldose; the specific name is the unknown. Jumping to glucose is the miss.

How it works

  1. Copy the nameThe given.
  2. Name sugar / protein / enzyme / vitamin / nucleic / hormoneThe unknown.
  3. Then classifyGiven first.
Enzymes at this class are
  1. Protein-catalysts that speed a named reaction
  2. Vitamins
  3. Starch grains

Speed-and-fit.

Notes

  • Mapped to the official NCERT chapter “Biomolecules”. Original teaching only — no textbook sentences.
  • Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.

Formulas

  • peptide: amino-acid link
  • DNA/RNA: nucleotide chains

Recap

Hold these pegs from the official chapter “Biomolecules”. The wording is ExamMaster’s teaching, not a textbook recap.

Carbohydrates
Carbohydrates: sugars and sugar-chains as taught — glucose, sucrose, starch, cellulose as cases.
Proteins
Proteins: amino-acid chains with a job as taught.
Enzymes
Enzymes: protein-catalysts that speed a named reaction as taught.
Vitamins
Vitamins: organic helpers needed in small amounts as taught, often from food.
Nucleic Acids
Nucleic acids: DNA and RNA as taught — information-chains of nucleotides.
Hormones
Hormones (chemistry size): chemical signals as taught — a named peptide or steroid if listed.

Practise Biomolecules

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