Biology Module 3 - Exchange of Materials

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Active Transport

  • Diffusion = net movement of particles from a high concentration to a low along a concentration gradient.
  • Osmosis = net movement of particles from a high concentration to a low through a partially permeable membrane.
  • Active Transport = movement of particles from a low concentration to a high (against the concentration gradient)
  • Examples of A.T :
  • = cells absorb ions from dilute solutions. 
  • = move substances like sugars and ions from one place to another through cell membranes.
  • = mineral ions in soil that are found in dilute solutions, through A.T, plants can absorb them. 
  • = glucose is moved out of the gut and kidney into the blood against the concentration gradient.
  • Energy is needed for A.T. which comes from cellular respiration.
  • Mitochondria usually found in cells which are used in A.T.
  • Marine birds and reptiles take in a lot of salt from sea water, kidneys cant get rid of it all :
  • - salt glands found near eyes and nostrils. Salt ions are moved out of body and into the glands. 

Exchange of Gases in Lungs

  • Body needs a constant supply of oxygen for cellular respiration. 
  • Breathing brings oxygen and removes carbon dioxide.
  • Lungs are found in the chest (thorax) protected by ribcage. They are separated from the digestive organs in the abdomen (lower part of your body) by the diaphragm (sheet of muscle). 
  • Job of breathing system : move air and in out of your lungs. 
  • It brings in oxygen and removes carbon dioxide.
  • When breathing in:
  • - ribs move up and out, diaphragm flattens from its normal dome shape.
  • - this pulls air into lungs.
  • When breathing out :
  • - ribs move down and in, diaphragm returns to its dome shape.
  • - the movement of shape, forces air out.
  • Adaptations for gas exchange (LUNGS) :
  • - large surface area
  • - moist
  • - rich blood supply (maintains conc gradient in both directions, oxygen is constantly delivered to the lungs so it takes place along the steepest conc gradient) 
  • - layer of cells between air in lungs and blood capillaries is thin.

Exchange in the gut

  • Food broken down in gut makes glucose, amino acids, fatty acids and glycerol.
  • Once they are broken down they need to move from the small intestine to the blood stream. This is done by a mixture of active transport and diffusion.
  • The digested food molecules are small enough to pass freely through the small intestine walls into the blood vessels.
  • They move from a high concentration to a low (diffusion)
  • The lining of the small intestine is folded into thousands of tiny finger like projections called villi. They increase the uptake of digested…


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