1.2 Transport across the Cell Membrane

• what are cell membrane composed of (not plant cell's membrane)?

  phospholipids, and proteins

  
• what is diffusion

  the movement of MOLECULES from a region of a HIGHER concentration to a LOWER concentration, down the concentration gradient. it's a passive process (meaning it requires NO energy)
• why is diffusion essential for cell?

  it is useful as it is how useful substances such as GLUCOSE and OXYGEN enters the cell and how waste products such as CARBON DIOXIDE and UREA leave the cell.
• what do you call the movement of WATER molecules from a HIGHER WATER CONCENTRATION to a LOWER WATER CONCENTRATION 


  Osmosis
• what happens to an animal cell when it is in pure water?

  in pure water, the animal cell will GAIN WATER by osmosis. this will cause the cell to SWELL and potentially burst.
• what happens to an animal cell when it is in a concentrated salt or sugar solution (low water)?

  the animal cell will LOSE WATER by osmosis. This will cause the cell to SHRINK and shrivel.
• what happens to a plant cell in pure water?

  the plant cell will gain water by osmosis, and cause the vacuole to swell and the cell to become turgid. the cell does not burst as it has a cell wall.

  
• what happens to a plant cell in a concentrated salt or sugar solution (low water)?

  the plant cell will LOSE WATER by osmosis, and the cell will become plasmolysed.

  
• what happens to an animal cell AND a plant cell when it is in a dilute solution (where the water concentration is equal inside and outside the cell)?

  osmosis still occurs, but there is no net flow of water, so the cell STAYS THE SAME.
• what is active transport?

  Movement of molecules from a LOW concentration to a high concentration AGAINST the concentration gradient. this requires energy (atp) and protein pumps.