Cambridge 0610 Topic 12.1–12.2 · Core and Supplement
Aerobic vs Anaerobic Respiration: A Complete Comparison
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Aerobic respiration uses oxygen, fully breaks down glucose to carbon dioxide and water, and releases a large amount of energy. Anaerobic respiration occurs without oxygen, partially breaks down glucose to lactic acid (in humans) or ethanol and carbon dioxide (in yeast), and releases much less energy.
This comparison is one of the most reliable exam questions. A table format scores best because it forces paired answers. Always state the specific product for each organism: human muscles produce lactic acid, yeast produces ethanol and carbon dioxide.
The comparison table
Feature
Aerobic
Anaerobic (humans)
Anaerobic (yeast)
Oxygen needed?
Yes
No
No
Equation
glucose + oxygen → CO₂ + water
glucose → lactic acid
glucose → ethanol + CO₂
Energy released
Large amount
Small amount
Small amount
Glucose breakdown
Complete
Incomplete
Incomplete
Where
Mitochondria
Cytoplasm
Cytoplasm
Why anaerobic releases less energy
In anaerobic respiration, glucose is only partially broken down. The products (lactic acid or ethanol) still contain significant amounts of chemical energy locked in their bonds. In aerobic respiration, glucose is completely broken down to carbon dioxide and water, which contain much less stored energy. Therefore aerobic respiration releases more of the original energy from each glucose molecule.
This is why aerobic respiration is the preferred pathway: it extracts far more energy per glucose molecule. Anaerobic respiration is a short-term supplement used only when oxygen is insufficient.
When each type occurs
Aerobic respiration occurs continuously in all living cells that have access to oxygen. It is the primary energy source for most organisms most of the time.
Anaerobic respiration occurs when oxygen supply is limited: in human muscles during intense exercise when blood cannot deliver oxygen fast enough; in yeast in sealed containers during fermentation; in waterlogged soil where plant roots have limited oxygen; and in bacteria in anaerobic environments.
In muscles, both aerobic and anaerobic respiration occur simultaneously during vigorous exercise: anaerobic does not switch on while aerobic switches off.
Try a focused question (2 marks)
State two differences between aerobic and anaerobic respiration in humans.
Show the answer and marking guidance
Aerobic respiration requires oxygen; anaerobic does not.
Aerobic produces carbon dioxide and water; anaerobic produces lactic acid.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Saying anaerobic respiration in humans produces ethanol: ethanol is produced by yeast.
Claiming anaerobic releases more energy because it happens during intense activity.
Saying aerobic respiration only happens during rest: it happens all the time.
Describing the two types as alternative rather than complementary during exercise.