Grade 8 · Ecosystems and Energy Flow · Energy Flow and Matter Cycling
Cellular Respiration and Energy Release
Releasing the energy stored in glucose — with and without oxygen.
Learning objectives
- Write the word equation for aerobic respiration.
- Compare aerobic and anaerobic respiration.
- Explain how respiration and photosynthesis are linked.
NGSS alignment
HS-LS1-7
Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed, resulting in a net transfer of energy.
MS-LS1-7
Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.
MYP criteria
- Criterion A — Knowing and Understanding
- Criterion C — Processing and Evaluating
ENGAGE
Why do your legs ache after a sprint?
After a hard sprint your muscles burn and you keep breathing heavily long after you stop running.
Think about it
- What is your body still catching up on?
- Why does walking not produce the same feeling?
EXPLAIN
Aerobic and anaerobic respiration
Aerobic respiration
glucose + oxygen gives carbon dioxide + water, releasing energy
| Feature | Aerobic | Anaerobic in muscle |
|---|---|---|
| Oxygen needed | Yes | No |
| Products | Carbon dioxide and water | Lactic acid |
| Energy released | Large amount | Small amount |
| Where | Mitochondria | Cytoplasm |
During intense exercise oxygen cannot be delivered fast enough, so muscle cells switch to anaerobic respiration. Lactic acid builds up and must be broken down later, which is why heavy breathing continues after exercise.
Careful
Respiration is not breathing. Breathing moves air; respiration is a chemical reaction inside cells.
Respiration and photosynthesis are opposites: the products of one are the reactants of the other, which recycles carbon and oxygen through ecosystems.
Watch
Cellular Respiration (Updated)
Amoeba Sisters · 8 min
Explains aerobic and anaerobic pathways clearly.
Before you watch: Why do you keep breathing hard after exercise stops?
- Where in the cell does aerobic respiration occur?
- What is produced in anaerobic respiration in muscle?
Interactive simulation · PhET
Energy Forms and Changes
Trace energy from a chemical store to useful work and to the surroundings.
While you explore
- Which energy store does glucose represent?
- Why do respiring cells release thermal energy?
Key vocabulary
- Anaerobic respiration
- Releasing energy from glucose without oxygen.
- Respiration
- How cells release energy from food.
Practice questions
0/2 correct
Level 1 · Criterion A
What are the products of aerobic respiration?
Level 2 · Criterion A
Anaerobic respiration in a muscle cell produces:
MYP criterion tasks
Level 3 · Criterion C
A student claims that plants respire only at night. Use evidence to evaluate this claim.
Reflect & track
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