Aerobic respiration

1Energy from food

Every living cell needs energy: to move, to grow and to stay warm. Cells release it from glucose, which comes from digested food. This chemical reaction is respiration.

respirationglucose

2The word summary

Aerobic respiration: glucose + oxygen → carbon dioxide + water. Aerobic means it uses oxygen. Glucose and oxygen are the reactants; carbon dioxide and water are the products. Energy is released.

aerobicreactantsproducts

3Mitochondria

Aerobic respiration happens inside mitochondria, tiny parts in the cytoplasm of almost every cell. Cells that need a lot of energy, such as muscle cells, have many mitochondria.

mitochondria

4What the energy is for

Respiration doesn't make energy: it releases energy stored in glucose. Cells use it to contract muscles, build new molecules for growth and repair, send nerve signals and keep you warm.

releases energy

5The limewater test

You can't see respiration, but you can test for its products. Carbon dioxide turns clear limewater cloudy. Breathed-out air turns it cloudy much faster than the air around us.

limewater

6Warm peas

Germinating peas respire. In a vacuum flask plugged with cotton wool, some of the energy they release warms them, so the thermometer rises. Boiled peas are dead and stay cool: they are the control.

control

7Plants respire too

Every living cell respires, all the time: plant cells and yeast as well as animal cells. In the light a leaf also photosynthesises, making the glucose its cells will respire.