Movement into and out of cell

• Active transport 


  The movement of particles through a cell membrane form a region of lower concentration to a religion of higher concentration against the concentration gradient using energy from respiration
• Mechanism of active transport

  • Carrier protein changes shape to move the molecules/ions through the carrier protein
  • Against the concentration gradient
  • From a low concentration to a high concentration
  • By using energy from respiration/mitochondria
• Examples of active transport process

  • Uptake of glucose by villi in small intestine
  • are absorption of glucose by kidney tubules
  • Uptake of mineral ions from soil water by root hair cells in plants
• Diffusion 


  • Substance can cross the cell membrane
  • Down the concentration gradient
  • DOES NOT need energy from respiration
  • Dissolved solutes
  • DOES NOT require a membrane
• Diffusion 


  • The net movement of particles /molecules from a region of higher concentration gradient to a region of lower concentration down the concentration gradient as a result of their random movement
  • Substances move in and out from the cells by diffusion through cell membrane
• Diffusion in living organisms

  • Gaseous exchange in unicellular organisms
  • Gaseous exchange between alveolus and blood capillaries during respiration
  • Gaseous exchange through the stomata of leaves
  • Absorption of gluscose into the blood of humans at small intestine
• Characteristics of alveolus


  Large surface area

  Thin wall //One cell thick

  Moist surface

  Surrounded by blood capillaries
• Why oxygen can move from through diffusion?

  Concentration of oxygen in alveolus is higher than blood capillaries
• Where does energy from diffusion come from?

  Comes from a random movement of molecules and ions
• What’s a gaseous exchange surface?

  a place where gases move between organism and its environment
• Factors influencing rate of diffusion 1

  Surface area - The larger the surface area of the exchange membrane the faster the particles diffuse

  Temperature - Increasing the temperature will give particles more kinetic energy making them faster, thus increasing the rate of diffusion
• Factors influencing the rate of diffusion 2

  Concentration gradient - the steeper the gradient the faster the particles diffuse

  Distance (Thickness) of exchange membrane - The thinner it is the easier it will be for particles to go through it, the faster the diffusion rate
• Before diffusion experiment 


  Starch solution in visiting tube is white

  Water outside visiting tube is yellow
• After experiment 


  Starch solution in visiting tubing turns blue black

  Watef outside viking tube remains yellow
• Explanation for experiment 


  Iodine solution diffuse into Visking tubing

  Iodine molecules are small enough to pass through membrane

  Iodine solution stains starch and no starch is diffused out of the viking tube as starch molecules are too large to pass through the viking tubing
• Plant cell placed in distilled water

  Water moves into cell by osmosis

  Cells get bigger and become TURGID

  Vacuole gets bigger and extra turgor pressure on cell wall

  Turgor pressure increases
• Animal cell (red blood cell )


  Water moves into the cell by osmosis

  Cell will burst and haemolysis occurs
• Plant cell placed in concentrated solution

  Water moves out from cell by osmosis

  Cells become flaccid and plasmolysed

  Vacuole becomes smaller /decreases in size

  Cell shrinks and turgor pressure increases
• Animal cell (red blood cell) placed in concentrated solution 


  Water moves out from the cell by osmosis

  Cell will shrink and cremation occurs
• Osmosis 


  The movement of water molecules from a region of high water potential to a region of lower water potential through a partially permeable membrane
• Water moves into plant cell by osmosis, state one benefit of this


  Becomes turgid / provides support
• Suggest why student dried the potato sticks before putting them on the electronic balance

  To remove excess water
• The students followed the same experimental procedure with boiled potato sticks and found no overall change

  Protein is denatured when cooked // cell membrane is damaged

  No osmosis occurs
• No osmosis occurs

  water moves in and out at the same rate
• Boiling potato, can osmosis still occur? state why

  No, as boiling destroys the potato’s cell membrane, and cell membrane is necessary for osmosis to occur
• Which structures need to present for osmosis to occur?

  Cytoplasm - has water

  Cell membrane
• Describe the changes that will occur in the cell during 30 mins in water

  [3marks]

  Water moves into cell by osmosis

  Cell gets bigger and becomes turgid

  Vacuole gets bigger and exerts turgor pressure on the cell wall, Turgor pressure increases
• Explain how root hair cells use osmosis to take up water

  Water moves from high water potential to low water potential from SOIL WATER to the root hair cells through partially permeable membrane [2marks]
• The land on which a cereal crop is growing is flooded by sea water suggest the effect sea water could have on cereal plants

  Sea water has a lower water potential/concentration

  Water moves out of the cell of cereal crop by osmosis

  Cells become flaccid and plasmolysed

  Cell shrinks and plants die
• is pore protein the same as carrier protein

  NO only CFTR proteins are
• Absorption of ions by root hair cells

  1. Carrier protein changes shape

  2. Moves molecules/ions through the carrier

  3. From low concentration to high concentration/against concentration gradient

  4. Uses energy from respiration/mitochondria
• Describe in which diffusion is different from active transport

  Diffusion does not require a membrane but active transport requires a membrane
• why capillaries can develop efficient absorption ?

  Capillary cells have pores