NDA Biology · Free notes
Biochemistry — NDA Biology
Biochemistry is a small chapter in NDA Biology — only a handful of EASY PYQs across 2017–2026, all pure recall about the chemistry of life. Because the bank is thin, this chapter is built foundation-first: it teaches the topic from zero — the four classes of biomolecules, how proteins are built and folded, how cells release energy with and without oxygen, and why food goes bad — so a student (or a teacher using it as a lesson plan) gets the whole picture, not just the four questions asked. The chapter teaches in three movements: (1) Biomolecules and protein structure — the four building blocks of life and the four levels of protein structure; (2) Respiration and fermentation — how cells make ATP, and what happens when oxygen runs out (alcoholic and lactic-acid fermentation); (3) Food spoilage — rancidity of fats and enzymatic browning of cut fruit, and how to prevent both. Learn the primary-structure definition, the yeast-fermentation products, and the oxidation behind rancidity and browning, and every PYQ here is free.
The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.
Subtopic notes
Biomolecules and Protein Structure
1 PYQsLiving things are built from four kinds of biomolecule — carbohydrates, proteins, lipids and nucleic acids; proteins are chains of amino acids joined by peptide bonds, folded through four structural levels.
Respiration and Fermentation
1 PYQsCells release energy from glucose as ATP; with oxygen this is aerobic respiration, and without oxygen it is anaerobic respiration or fermentation — which in yeast yields ethanol and carbon dioxide, and in muscle yields lactic acid.
Food Spoilage — Rancidity and Browning
2 PYQsFood goes bad mainly through oxidation: fats and oils turn rancid when oxidised by air, and cut fruit browns when the enzyme polyphenol oxidase oxidises its compounds — both slowed by keeping oxygen away.
Formula & revision sheet
4 formulas · 1 reference tables · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
4 formulas · 1 reference tables · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (1)
The four levels of protein structure4 rows
| Level | What it is |
|---|---|
| Primary | The linear sequence of amino acids joined by peptide bonds 'A linear sequence of amino acids linked by peptide bonds' = PRIMARY structure — the bank's exact phrasing. |
| Secondary | Local coiling/folding into an α-helix or β-pleated sheet, held by hydrogen bonds |
| Tertiary | The overall 3-D folded shape of a single polypeptide chain |
| Quaternary | Two or more folded chains (subunits) assembled together (e.g. haemoglobin = 4 subunits) |
Watch out for (1)
- Linear sequence + peptide bonds = PRIMARY, not secondary→ The four levels of protein structure
Formulas (2)
Watch out for (1)
- Yeast makes ethanol + CO₂; muscle makes lactic acid→ Fermentation — alcoholic and lactic acid
Formulas (2)
Watch out for (3)
- Rancidity is OXIDATION, not reduction or freezing→ Rancidity — the oxidation of fats and oils
- Lemon juice stops browning — not sugar or milk of magnesia→ Enzymatic browning of cut fruit
- Rancidity vs enzymatic browning→ Enzymatic browning of cut fruit
PYQ weightage by concept
6 concepts · 4 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
6 concepts · 4 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| The four levels of protein structure | 1 | 25% |
| The four biomolecules of lifefoundation | — | — |
| Concept | PYQs | Share |
|---|---|---|
| Fermentation — alcoholic and lactic acid | 1 | 25% |
| How cells release energy — aerobic vs anaerobicfoundation | — | — |
| Concept | PYQs | Share |
|---|---|---|
| Rancidity — the oxidation of fats and oils | 1 | 25% |
| Enzymatic browning of cut fruit | 1 | 25% |
Test yourself on a real paper
Sit a past NDA paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.