Diffusion, osmosis & active transport

• diffusion


  the spreading out of particles from a high concentration to a low concentration
• temperature effect on diffusion

  higher diffusion rate - the particles have more energy so move around faster
• only very small molecules can fit though the cell membrane such as oxygen and water but big molecules like starch and protein cant
• things that increase the rate of diffusion

  large surface area

  large difference in concentration / steep concentration gradient

  high temperature
• osmosis

  movement of water molecules across a partially permeable membrane from an area of high water concentration to an area of low water concentration
• partially permeable membrane means

  only small molecules can get through
• where does diffusion happen

  solution or gas
• osmosis happens with water
• A boy adds blackcurrant squash to water in a normal pint glass. State if this experiment is an example of osmosis and explain why.

  it is not osmosis because the water molecules do not have to travel through a partially permeable membrane
• the net movement is to the right as water wants to move from a high concentration of water to a low concentration of water due to osmosis

  
• hypertonic


  higher concentration of water outside of the cell

  causes water to move out of cell

  cell will shrivel
• hypotonic


  lower concentration of water outside of the cell

  causes water to move into the cell

  cell will expand and burst
• isotonic


  same concentration of water inside and outside of the cell

  cell does not change
• active transport


  moves against the concentration gradient and requires energy from respiration
• root hair cells take in minerals by

  active transport
• active transport in root hair cells

  there is a higher concentration of ions in a root hair cell than in the soil and it gains more by active transport
• active transport in the gut


  when there is a lower concentration of nutrients in the gut but a higher concentration in the blood. active transport allows nutrients to go into the blood
• two examples of when active transport is used

  root hair cells

  in the gut