diffusion

• the rate of diffusion depends on temperature, surface area, pressure gradient and distance travelled
• surface area affects how many molecules can diffuse out at once
• the rate of diffusion depends on temperature, surface area, pressure gradient and distance travelled
• diffusion is the movement of particles from an area of high concentration to low concentration
• in passive transport, substances move down their own concentration gradients without using energy
• diffusion occurs when particles move randomly until they reach an equilibrium state where there are equal numbers of particles on both sides of the membrane
• diffusion occurs when there is an uneven distribution of particles across a membrane or solution
• active transport requires ATP as it moves against its concentration gradient
• diffusion occurs when there are more particles on one side than another
• osmosis is the diffusion of water across a partially permeable membrane
• osmosis is when water passes through a partially permeable membrane from an area of lower solute concetration to higher solute concentration
• pure water has a water potential of 0
• concentration is used for solutes = cannot use for osmosis
• low Y than cell, high concentration
• Hypotonic solutions 


  Little of solute, high water potential than cell, low concentration
• Isotonic solution 


  Same water potential as cell
• Lysis


  Rupture or bursting of a cell due to too much water
• Turgid

  Full of water
• Flaccid


  Lacking in stiffness
• Plasmolysed


  Membrane comes away from wall
• Diffusion


  Substances move from a high to a low concentration, down a concentration gradient
• Osmosis


  Water moves from a high to a low concentration, across a partially permeable membrane and down a concentration gradient
• Descriptions


  • Substances move from a high to a low concentration, down a concentration gradient
  • Water moves from a high to a low concentration, across a partially permeable membrane and down a concentration gradient
• Substances moved for diffusion


  • Carbon dioxide
  • Oxygen
  • Water
  • Food
  • Substances
  • Wasies
• Active transport


  Substances move against a concentration gradient
• Substances moved by active transport

  • Mineral ions into plant roots
  • Glucose from the gut into intestinal cells
• the rate of osmosis depends on temperature, surface area and pressure difference
• if the solute concentration inside the cell is higher than outside, water will diffuse into the cell by osmosis
• if the solute concentration outside the cell is higher than inside, water will diffuse out by osmosis
• distance affects the rate of diffusion because if the distance between two areas decreases then the time taken for particles to diffuse will decrease
• water usually has a water potential that is more negative due to dissolved solutes making it no longer 100% water molecules
• water potential is measured in kilopascals
• hypertonic solution- lots of the solute, lower water potential than cell, high concentration
• cremate- cell membrane shrinks