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  • Created by: Ryan
  • Created on: 19-05-12 11:37

Biology - Diffusion / Active transport

Diffusion / Active transport -

  • Diffusion is when particles move from a 'high concentration to a low concentration' through a 'partially permiable membrane'.
  • The rate at which diffusion happens will depend on the difference in concentration on each side of the membrane, this is called the 'concentration graident'.
  • The more particles in a one place, the quciker the rate of diffusion.
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Biology - Lungs / Gas exchange

Gas exchange in the lungs -

  • The lungs are located in the 'thorax', protected by the ribcage.
  • The 'diaphragm' is below the lungs and separates the 'thorax' and the 'abdomen'.
  • When you breathe in, your ribs move up and the diaphragm down. When you breathe out, your ribs move down and the diapragm up.
  • The widest tubes inside your lungs are called 'bronchi'. They link the lungs to the windpipe that goes to your throat.
  • The tubes branch out and get narrower as they go deeper into the lungs. Eventually each tube ends in a tiny air sac called 'alveolus'. The 'alveoli' is what the exchange between oxygen and carbon dioxide happens in.
  • Some of the air in your lungs is replaced each time oyu breathe. This keeps a relatively high concentration of oxygen and a low concentration of carbon dioxde. Meanwhile, the blood capillaries are continuously circulating, bring blood to the lungs with a high concentration of carbon dioxide and a low concentration of oxygen.
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Biology - Absorbing food

Absorbing food -

  • The inner surface of the intestines is covered in small 'projections' called 'villi'. They increase the surface area of absorbtion. By the time the food passes through the 'small intestine', it has the consistency of mushy soup. Muscles in the intestine's wall help make the 'villi' swat from side to side througth the 'soup' and bring them into contact with as much of it as possible.
  • Many of the cells that line the 'villi' have tiny 'projections' on them called 'microvilli'. These cells form a surface that is one cell thick and is close to the 'capillaries' inside each 'villus'. Each capillary also has a wall that is only one cell thick si the distance the absorbed substances have to 'travel' to get into the blood is minimum.
  • The movement of the digested food from the gut to the blood is 'diffusion'. The things that diffuse are mostly molecules of fats (glycerol and fatty acids), and water and mineral ions.
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Biology - Absorption / Plants

Absorption in plants -

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