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Respiration and Gas Exchange
Respiration:
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Respiration goes on in every cell in the body
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Energy is released as chemical and heat energy
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The heat energy helps to maintain a steady body
temperature
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Aerobic:
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What happens when there’s plenty of oxygen available
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This is the most used type of respiration
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Anaerobic:
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When you do vigorous exercise, your body can’t supply enough oxygen to you
muscles for aerobic respiration, even though your heart rate and breathing rate
increase as much as they can
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The lactic acid builds up in the muscles; it gets painful and leads to cramps
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For Plants:
o Glucose  Ethanol + Carbon Dioxide (+Energy)
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When plants respire, they use up O2 and produce CO2 as a waste product
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Luckily, this makes more CO2 move into the leaf by diffusion
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Some is used in respiration, and the rest diffuses out through the stomata
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They’re also thin, which means gases only have to travel a short distance to reach
the cells where they’re needed
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This lets gases like carbon dioxide and oxygen
move easily between cells
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The lower surface is full of little holes called stomata
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They also allow water to escape
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Photosynthesis can’t happen in the dark, so
they don’t need to be open to let CO2 in
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Stomata also close when supplies of water from the roots start to dry up
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The opening and closing of the stomata is controlled by the guard cells around them
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It is separated from the lower part by the diaphragm
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They’re surrounded
by the plural membrane
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This splits into two tubes called
bronchi, one going to each lung
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The bronchioles end at small sacs called alveoli where the gas exchange takes place
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Thorax volume increases
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Breathing Out:
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Intercostal muscles and diaphragm relax
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Air is forced out
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The blood passing next to the alveoli has just returned from the rest of the body, so
it contains lots of carbon dioxide and very little oxygen
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Carbon dioxide diffuses out of the blood and into the
alveolus to be breathed out
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At the same time, carbon dioxide diffuses out of the cells into the blood
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Alveoli:
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The huge number of microscopic alveoli gives the lungs a huge surface area
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The alveoli have very thin walls – only one cell thick, so the gas doesn’t have to travel
far
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The walls are permeable – gases can diffuse across easily
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The tar in cigarettes damages the cilia (little hairs) in your lungs and trachea
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The cilia also help to keep the trachea clear by sweeping mucus back towards
the mouth
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Tar also irritates the bronchi and bronchioles, encouraging mucus to be produced
which can’t be cleared very well by damaged cilia
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The carbon monoxide in cigarette smoke reduces the amount of oxygen the blood
can carry
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High blood pressure damages the artery walls, making the formation
of blood clots more likely
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Tobacco smoke also contains carcinogens – chemicals which can lead to cancer

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