Define aerobic respiration in cells
Keep oxygen use, nutrient breakdown and energy release together.
Section B12.1 · Respiration
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall cell processes, enzymes and the distinction between gas exchange and breathing.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where do cellular chemical reactions occur?
What you will learn
- Describe the chemical process
- Apply the definition precisely
Define aerobic respiration in cells
| Feature | Meaning |
|---|---|
| Location | Cells |
| Input condition | Oxygen used |
| Process | Nutrient molecules broken down |
| Outcome | Energy released |
Describe the chemical process
Aerobic respiration is a set of chemical reactions in cells that uses oxygen to break down nutrient molecules and release energy. Each part matters: it is chemical, cellular, oxygen-using and energy-releasing. Breathing air into the lungs supplies a material used by many cells, but breathing itself is not the chemical breakdown process.
Glucose is the nutrient used in the syllabus equations. It is not the only nutrient that organisms can use, so the general definition says nutrient molecules. The equations in this sequence use glucose as the specified example. Avoid saying that oxygen is the food or that energy is created; oxygen is a reactant and energy is released from the breakdown process.
Apply the definition precisely
Aerobic respiration occurs in animal and plant cells. A plant does not stop needing respiration because it can photosynthesise: its cells still require energy for transport, synthesis, growth and other work. Do not assume that an organism respires only in the organ that exchanges gas, such as a lung or leaf.
In a supplied scenario, look for oxygen being used in cellular nutrient breakdown, rather than merely for oxygen somewhere nearby. The presence of oxygen around a sample is not, by itself, a direct measurement of the reaction rate. Combine the described reaction with the definition, and reserve exact rate conclusions for appropriately controlled measurements.
Sources for this lesson
Pause and explain
Which definition has all essential aerobic features?
Worked example
A cell uses oxygen while breaking down glucose and releasing energy. Classify the process.
Show the worked solution
- Oxygen is used in nutrient breakdown.
- The reactions occur in a cell and release energy.
Answer Aerobic respiration.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Give a complete definition of aerobic respiration.
Give me a hint
Use location, oxygen, breakdown and energy.
Compare my reasoning
- State chemical reactions in cells.
- Add oxygen use, nutrient breakdown and energy release.
Chemical reactions in cells use oxygen to break down nutrient molecules and release energy.
Look for these in your work
- Include oxygen use
- Include cellular breakdown and release
Correct: aerobic respiration is oxygen becoming food in the lungs.
Give me a hint
Identify oxygen as a reactant, not food being formed.
Compare my reasoning
- Nutrients are broken down in cells.
- Oxygen is used and energy is released.
Aerobic respiration uses oxygen in cellular nutrient breakdown to release energy; it is not oxygen becoming food in lungs.
Look for these in your work
- Correct location and process
- Retain the energy link
A plant root cell uses oxygen to break down glucose. Does being a plant rule out aerobic respiration?
Give me a hint
Plant cells also need energy.
Compare my reasoning
- The stated reaction uses oxygen and nutrient breakdown.
- That matches the same cellular definition.
No. The stated root-cell process is aerobic respiration, supplying energy for plant cell work.
Look for these in your work
- Apply the definition
- Avoid an animal-only rule
Common mistakes
- Defining it as breathing.
- Calling oxygen the nutrient fuel.
What can you explain now?
Which definition has all essential aerobic features?
Compare with the explanation
Cell reactions use oxygen to break down nutrients and release energy
All the defining features are present.
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Make it stick
State every part of the aerobic definition.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.