Chapter 1. Respiration FREE
Every living cell needs energy to stay alive. Respiration is the process in which cells release energy from food. It happens all the time, in every living thing, day and night.
Aerobic respiration
In aerobic respiration, cells use oxygen to break down glucose, releasing energy. Carbon dioxide and water are produced as waste.
The word equation
glucose + oxygen → carbon dioxide + water + energy
Why living things need energy
Living things use the energy from respiration to move, grow, repair injuries, stay warm and carry out all the activities of life.
Respiration and photosynthesis
Respiration is almost the reverse of photosynthesis. Photosynthesis stores energy from the Sun in glucose; respiration releases that energy again. Green plants do both, while animals only respire.
Breathing is not respiration
Breathing moves air in and out of the lungs. Respiration releases energy inside cells. Breathing supplies the oxygen that respiration needs and removes the carbon dioxide it makes, but the two are not the same process.
Worked example
A learner runs in a race and breathes faster. Why? Hard exercise needs more energy, so the muscle cells respire faster. They need more oxygen and produce more carbon dioxide, so breathing speeds up to keep up with respiration.
Common errors
- Thinking breathing and respiration are the same thing.
- Saying respiration makes energy. Energy is released from glucose, not created.
- Forgetting that plants respire too, not only animals.
Practice
- Which gas does aerobic respiration use?
- Name the two waste products of aerobic respiration.
- Give one reason living things need energy.
Solutions
- Oxygen.
- Carbon dioxide and water.
- To move, grow, repair, or stay warm (any one).
Summary
Respiration releases energy from glucose in every living cell. Aerobic respiration uses oxygen and produces carbon dioxide and water. It is almost the reverse of photosynthesis, and it is different from breathing, which only moves air in and out of the lungs.