Respiration 01

This KS3 Science quiz asks questions on respiration. In everyday life, there will be times when you will hear the words breathing and respiration used to mean the same thing. This can be a bit confusing because in schools, we use the word respiration to describe the release of energy in living cells (it should really be called cellular respiration but that's a bit of a mouthful so teachers often shorten it!).

Breathing is the process by which animals with lungs move air into and out of their respiratory system. This enables their bodies to extract oxygen from the air and to return carbon dioxide to the air. The air is a mixture, mainly nitrogen (78%) and oxygen (21%) with about 1% of other gases including argon, water vapour and carbon dioxide. During breathing, air from outside of the body enters the respiratory system through the nose and mouth (it's better through the nose as it warms and filters the air) and passes down the windpipe (trachea).

The bottom of the windpipe is split into two bronchi which direct the air into the two lungs. Inside of the lungs, the bronchi are divided into lots of even smaller tubes called bronchioles. These end in air sacs (alveoli) which are covered in blood capillaries. This is where oxygen gets into the bloodstream and the waste carbon dioxide gets out.