Cambridge IGCSE Biology 0610 · Topic 12
Respiration
Every living cell needs a continuous supply of usable energy, and respiration is where that energy comes from. Underneath the different-sounding questions in this chapter — uses of energy, yeast at different temperatures, aerobic equations, lactic acid in tired muscles — there is really one relationship doing all the work: whether oxygen is available, and what that does to how much energy a cell can pull out of a single glucose molecule. Once you can see the chapter that way, aerobic and anaerobic respiration stop feeling like two separate topics to memorise and start feeling like the same question, answered from two directions.
Cambridge organises this material under three syllabus points — 12.1 Respiration, 12.2 Aerobic respiration and 12.3 Anaerobic respiration — and IGCSE Biology respiration questions draw on all three, often in the same structured question. Core candidates need to know what respiration’s energy is actually used for, how temperature changes the rate of respiration in yeast, the definition and word equation for aerobic respiration, and the meaning and word equations for anaerobic respiration in both yeast and muscle. Supplement candidates go further, into the balanced chemical equations and into what happens to the lactic acid an exercising muscle leaves behind.
Students tend to lose marks here less because the biology is unfamiliar, and more because they blur distinctions Cambridge keeps sharp: respiration is not breathing, “less energy” is not the same as “much less energy per glucose molecule,” and yeast does not produce the same anaerobic products as muscle. The pages below are written to close exactly those gaps — not more facts, but the precise wording and the causal chains a Cambridge mark scheme is actually built around.
What’s in this chapter
| Page | Level | What it covers |
|---|---|---|
| Respiration and the uses of energy | Core | The seven named uses of respiration’s energy Cambridge actually requires, and why respiration and breathing are not the same process at all. |
| Temperature and respiration in yeast | Core | Why the rate rises with temperature up to a point and then collapses, and how to design a fair-test investigation around it. |
| Aerobic respiration | Core + Supplement | The definition and word equation every candidate needs, plus the balanced chemical equation required at Supplement. |
| Anaerobic respiration | Core + Supplement | Why yeast and muscle cells respire without oxygen, why they form different products, and how the oxygen debt is repaid. |
Core or Supplement?
Respiration and the uses of energy, and temperature and respiration in yeast, are Core throughout — every candidate needs them regardless of tier. Aerobic respiration and anaerobic respiration are Core in their definitions and word equations, but each carries genuine Supplement-only material on top: the balanced chemical equations for both processes, and the full lactic acid and oxygen debt story for anaerobic respiration in muscle. If you’re not sure which tier you’re sitting, it’s worth checking before you spend time memorising the balanced equations or the oxygen debt removal sequence, since none of the Core word equations depend on them.