Diffusion and Active Transport

  • Created by: India.02
  • Created on: 11-05-19 19:12
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  • Diffusion and Active Transport
    • Diffusion
      • Gradual movement of particles from an area of high concentration to an area of low concentration
      • Happens in solutions and gases - these particles are free to move randomly
      • The bigger the concentration gradient (difference in concentration) - the faster the diffusion rate
        • Higher temperature will give a faster diffusion rate because the particles will have more energy and will move around faster
      • Cell Membranes
        • Dissolved substances can move in and out of cells by diffusion, through the cell membrane
        • Particles flow through the cell membrane from where the concentrations highest to where the concentration is lowest
          • Particles move randomly but if there are a lot more particles on one side of the membrane, there will be a net movement from that side (overall)
          • Larger the surface area of the membrane, the faster the diffusion rate - more particles can pass through at once
    • Active Transport
      • We need it
        • Used in the gut when there is a low concentration of nutrients, but a higher concentration in the blood
        • When there is a higher concentration of glucose and amino acids in the gut, they diffuse naturally into the gut
        • BUT - sometimes there is a lower concentration of nutrients in the gut than there is in the gut
          • Concentration gradient is the wrong way - low to high concentration
        • Allows nutrients to be taken back into the blood despite the fact that the concentration gradient is the wrong way
          • Glucose can also be taken into the bloodstream when its concentration in the blood is already higher than in the gut - transpired to cells for respiration
      • Root Hair Cells
        • Each branch of a root will be covered in microscopic hairs that stick into the soil
          • Gives large surface area for absorbing water and mineral ions from soil - needed for healthy growth
            • Concentration of minerals is usually higher in the root hair cells than the soil around them - root hair cells can't use diffusion to take up minerals
        • Active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient - essential for growth but needs energy from respiration to work

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