Edexcel iGCSE Biology-2.44B Gas Exchange: Night vs Day- Study Notes- New Syllabus
Edexcel iGCSE Biology-2.44B Gas Exchange: Night vs Day- Study Notes- New syllabus
Edexcel iGCSE Biology-2.44B Gas Exchange: Night vs Day- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
2.44B understand how respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light
Respiration & Net Gas Exchange in Plants
📝 Key Idea
Respiration happens all the time (day & night).
Photosynthesis happens only in light.
The net gas exchange (overall movement of O₂ & CO₂) depends on light intensity.
🔄 Gas Exchange Explained
🌙 At Night (no light)
- Respiration only (since photosynthesis cannot occur without light).
- Oxygen taken in.
- Carbon dioxide released.
- Net exchange → O₂ in, CO₂ out.
🌥️ Low Light (dim conditions)
- Photosynthesis = Respiration rate.
- The gases used in photosynthesis balance those produced in respiration.
- No net gas exchange (O₂ in = O₂ out, CO₂ in = CO₂ out).
- This is called the compensation point.
🌞 Bright Light (daytime)
- Photosynthesis rate > Respiration rate.
- CO₂ used in photosynthesis is greater than CO₂ released by respiration.
- O₂ released is greater than O₂ consumed.
- Net exchange → O₂ out, CO₂ in.
📊 Summary Table
| Light Condition | Active Processes | Net Gas Exchange |
|---|---|---|
| Night (no light) | Respiration only | O₂ in, CO₂ out |
| Low light | Photosynthesis = Respiration | No net exchange |
| Bright light | Photosynthesis > Respiration | O₂ out, CO₂ in |
⚡ Quick Recap
Night → Respiration only → O₂ in, CO₂ out.
Low light → Balance → No net movement.
Day → Photosynthesis dominates → O₂ out, CO₂ in.
Respiration = always on, photosynthesis = light-dependent.