Respiration & Gas Exchange

What this lesson covers

Respiration & Gas Exchange is a 7-part O Level Biology lesson. Each part makes one point and then hands over to the next, so it can be read in a sitting or picked up again at the part you stopped on. It defines the idea in plain words before using it, works through an example step by step, breaks the topic into its parts and compares them, names the mistakes that cost marks in an exam, ends with a recap of what to remember.

How it begins

Respiration is the chemical release of energy from glucose, in every living cell, all the time. Breathing (ventilation) is the physical movement of air. Using one word for the other is the fastest way to lose a mark in this topic. Aerobic respiration: glucose + oxygen → carbon dioxide + water, releasing a large amount of energy. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. It happens in the mitochondria.

The 7 parts

1. Respiration is not breathing
2. Oxygen debt, and why anaerobic respiration cannot last
3. Breathing: the mechanism, in order
4. Alveoli, and comparing inhaled with exhaled air
5. Where marks go
6. What to remember
7. Watch one worked through