Cellular respiration at Higher Level: The same ideas as SL, with different examples: seeds living on their stores in the dark and the Arctic tern's record migration. At HL, expect to link respiration to the energy budget of whole organisms.
Practise this as you read
- Outline respiration as four points: where, what, which form, what for.
- Link faster activity to faster respiration, using data.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
Unlocking the energy in food: cellular respiration releases the energy stored in glucose and turns it into a chemical form that cells can use straight away.
The points to remember
- Cellular respiration happens in every living cell, day and night.
- It breaks down glucose and releases the energy stored in it.
- It turns that energy into a chemical form the cell can use easily.
- Plants respire all the time too; they photosynthesise only in the light.
- In words (see 2.2.3): glucose + oxygen → carbon dioxide + water.
- Not all the energy reaches the usable form: some is released as heat (see 2.2.7).
Remember it as: Glucose is the fuel; respiration hands the cell its usable energy.
Real example: a bean seed buried in dark soil cannot photosynthesise yet. It lives on its stored food, respiring it for energy, until its first leaves reach the light.
Two common mistakes: Respiration releases energy; it does not make it (energy cannot be created, see 2.2.2). And respiration is not breathing: breathing moves air in and out of the lungs, while respiration happens inside every cell.
Get feedback like a real examiner
Submit your answers and get instant feedback — what you did well, what's missing, and exactly what to write to score full marks.
Why do cells need this energy? Every job that keeps a cell alive and working is an active process.
What cells use the energy for
- The released energy powers active processes: jobs a cell does that need energy.
- Movement: muscles contracting, a heart beating.
- Growth and repair: building new cells and body tissue.
- Active transport: pumping substances into or out of cells, such as roots taking in minerals.
- Nerve impulses, and making new chemicals the body needs.
- More activity means faster respiration: more glucose and oxygen are used.
Remember it as: Move, grow, repair, pump, signal: all paid for by respiration.
Animals
- Muscles move the body.
- Nerves carry messages.
Plants
- Roots pump in minerals.
- New leaves and shoots grow.
Every cell
- Repairs damage.
- Builds new chemicals.
Real example: the Arctic tern, a seabird of about 100 g, flies about 70,000 km a year between the Arctic and Antarctica. Its flight muscles respire fast for months on end, fuelled by the fish it catches on the way.
How this could come up: Paper 2, Section B (a): outline a process, one point per mark [4].
An Arctic tern flies about 70,000 km a year between the Arctic and Antarctica.
Outline how cellular respiration provides the energy for active processes in living cells.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.