NDA Biology · Teaching 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.
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.
Open note
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.
Open note
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.
Open note
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% |
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