Bioenergetics is a core part of GCSE Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
PhotosynthesisPlants make glucose from CO₂ + water using light
ChloroplastPlant cell part where photosynthesis happens
Aerobic respirationReleases energy using oxygen, in mitochondria
Anaerobic respirationReleases energy without oxygen, less energy
Lactic acidAnimal anaerobic product, builds up in muscles
FermentationYeast anaerobic: makes ethanol + CO₂
StarchPlant glucose store — insoluble, won't change water balance
CellulosePolymer of glucose that strengthens plant cell walls
Oxygen debtExtra oxygen needed after exercise to clear lactic acid
EPOCExcess Post-exercise Oxygen Consumption — heavy breathing
ATPMolecule that delivers usable energy to cells
LiverOrgan that converts lactic acid back to glucose
Limiting factorThe factor that stops the rate going faster
Light intensityAmount of light energy hitting an area
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Where do plants get most of their biomass from?✗ Plants get most of their mass from the soil through their roots. ✓ From carbon dioxide in the air — the carbon in plant tissue comes mostly from CO2 fixed during photosynthesis.
What is produced in anaerobic respiration in human muscle cells?✗ Anaerobic respiration produces ethanol and CO2 in humans. ✓ Lactic acid (lactate) and a small amount of ATP — no CO2 or water in this pathway.
Do plants only respire at night?✗ Plants only respire at night and only photosynthesise during the day. ✓ No — plants respire all the time, day and night. In daylight they also photosynthesise, often faster than they respire.
Is energy 'created' as it passes along a food chain?✗ Energy is created at each link in a food chain so predators have the most. ✓ No — energy is transferred and much is lost as heat at each step; it is never created.
What does yeast produce by anaerobic respiration?✗ Lactic acid only ✓ Ethanol + carbon dioxide
Practise Bioenergetics — free games
Test yourself with these quick revision games for this topic:
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