Respiration (KS3)
🔑 What is Respiration?
Respiration is the process that releases energy from food (mainly glucose).
This energy is used for:
- Moving our muscles 💪
- Keeping our body warm 🌡️
- Building new molecules (like proteins) 🧱
👉 Remember: Respiration ≠ Breathing.
- Breathing = moving air in and out of your lungs.
- Respiration = chemical reaction inside your cells that releases energy.
1️⃣ Respiration is a Chemical Reaction
- Happens in every living cell (plants, animals, fungi, bacteria).
- It breaks down glucose to release energy.
- The reaction happens in mitochondria (tiny “power stations” inside cells).
2️⃣ Aerobic Respiration (with oxygen)
This is the “normal” type of respiration.
- Reactants: glucose + oxygen
- Products: carbon dioxide + water + energy
Word equation:
glucose + oxygen → carbon dioxide + water (+ energy)
💡 This reaction releases lots of energy, enough for everyday activities like walking, thinking, and digestion.
📍 Example: When you jog at a steady pace, your muscles get plenty of oxygen, so they respire aerobically.
3️⃣ Anaerobic Respiration (without oxygen)
Sometimes cells don’t get enough oxygen (e.g., during sprinting). Then they switch to anaerobic respiration.
In animals (including humans):
glucose → lactic acid (+ energy)
- Produces less energy than aerobic respiration.
- Lactic acid builds up in muscles → cramps and pain.
In yeast and some microorganisms:
glucose → carbon dioxide + ethanol (+ energy)
- This process is called fermentation.
- Humans use it to make bread, beer, and wine.
4️⃣ Comparing Aerobic vs Anaerobic
| Feature | Aerobic Respiration 🫁 | Anaerobic Respiration 💨 |
|---|---|---|
| Oxygen required? | ✅ Yes | ❌ No |
| Products (in humans) | CO₂ + H₂O | Lactic acid |
| Energy released | Large amount ⚡ | Small amount 🔋 |
| Useful for… | Normal daily activity | Short bursts (sprints) |
5️⃣ Why Respiration Matters
Without respiration:
- Muscles couldn’t move
- Brains couldn’t think
- Cells couldn’t survive
It’s the reason every living thing stays alive!
✨ Quick Check Questions (for practice):
- Where in the cell does respiration take place?
- Write the word equation for aerobic respiration.
- What causes muscle cramps during hard exercise?
- Name one product of anaerobic respiration in yeast.