Science Quiz - Respiration 01 (Answers)
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.
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You can find more about this topic by visiting BBC Bitesize - Respiration
That's about one fifth
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It is a common misunderstanding to think that all of the oxygen that goes into the lungs is taken into the body. If it was, mouth to mouth resuscitation would not be possible
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There is only a very small percentage of carbon dioxide in the air but it is enough to create a greenhouse effect that keeps the Earth warm enough to support life. Since the middle of the twentieth century, the percentage of carbon dioxide has increased faster than ever before. This increases the greenhouse effect and causes global warming
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That is significantly higher than the amount breathed in. It is a common misunderstanding that we breathe out only carbon dioxide
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The percentage of water vapour increases in exhaled air
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The walls of the alveoli are very thin and covered in blood capillaries. This allows the red blood cells to absorb oxygen as they pass through the lungs
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They have a very large surface area which makes the absorption of oxygen and removal of carbon dioxide as efficient as possible. Smoking damages the alveoli and so getting oxygen into the blood is a lot harder
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Haemoglobin in red blood cells joins with oxygen
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The carbon dioxide is released from all living cells during cellular respiration
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The animal uses its chest muscles to increase the volume of its lungs. The air inside the lungs is therefore more spread out than before, so it has a lower pressure. The higher pressure of the air outside of the lungs forces air into the lungs. The opposite is true of breathing out
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