Biology: Transport Across Cell Membranes

Biology: Transport Across Cell Membranes

1. Diffusion

   • The closer to the gas = the higher the concentration
   • Oxygen and Glucose go into the cell, Carbon Dioxide comes out the cell
   • Not all materials can diffuse
   • The higher concentration moves to the lower concentration
     • This like a ball rolling down a hill, no energy is required
       • This is called passive transport

2. Osmosis

   • Diffusion with water
   • The more water a plant absorbs, the heavier the plant is
   • Is required to get through selectively permeable membranes
     • A membrane that can decide what goes through and what doesn't
   • Osmosis moves from high water concentration to low water concentration
     • This is like a ball rolling down a hill, no energy is required
       • This is called passive transport
   • In plants, if too much water is absorbed, it will make the vacoule expand
     • This is known as a turgid cell
     • In animals, if there is too little water, the cell will shrivel up
     • It does not burst as plant cells have a cell wall
   • In plants, if there is not enough water, it will shrivel up
     • Thi is known as a plasmolysed cell
   • In animals, if there is too much water, the cell will burst!

3. Active transport

   • This is when the low concentration moves to the high concentration
     • Like a ball. It can't go uphill so you will have to push it. This requires energy