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Osmosis, diffusion, active transport and transpiration. (Osmosis,…

- - - - Higher water potential means less solutes
        dissolved in the water.
      - Names of different states of cells
        
        Red blood cells
        
        When too much water comes
        into a red blood cell it lyses/ Bursts
        
        When the water potential is equal
        inside and outside the cell there is no water
        potential gradient and the cell is in equilibrium. Plant
        cells want to be in that state.
        
        When the water potential is lower outside the cell
        and water leaves the cell, it is called crenated/shrivelled (in red blood cells)
        
        Plant cells #
        
        When water is entering
        the cell the will become turgid. This is
        the optimal state for plant cells
        
        At equilibrium it is called flaccid
        
        When water is leaving it is called plasmolysed
  - - - Factors that affect diffusion
        
        Temperature
        
        More temperature = more diffusion
        this is as molecules gain more kinetic energy
        and move around faster meaning more molecules
        move down the concentration gradient in a given time.
        
        Concentration gradient
        
        The steeper the concentration gradient (amount of atoms outside the cell compared to inside the cell) the faster diffusion
        will take place.
        
        Diffusion distance.
        
        The shorter the diffusion distance the faster the rate of
        diffusion will be.
        
        Surface area
        
        More surface area the faster the rate of diffusion.
        
        Surface area : volume ratio
        the higher the surface area is and the lower the volume is the better.
      - The reason single celled organisms that lack
        a special circulatory system to special gas exchange mechanism
        cannot grow above a certain size.
        
        Single cells without these special functions rely on diffusion to
        survive. The bigger an organism gets the the lower the surface area: volume ratio is, decreasing diffusion meaning that the organism would die. Also the bigger the cell gets the larger the further the distance is between the cell membrane and the centre of the cell and as diffusion doesn’t work well over large distances the cell will struggle to survive.
  - - - The selectively permeable
        membrane has pump like features that use energy to move particles against the concentration gradient.
        
        Transpiration, osmosis and
        diffusion are all passive but active transport is active.
      - The reason diffusion doesn’t happen passively and active
        transport does is because the selectively permeable membrane doesn’t let the particles from the high concentration area enter the low concentration area.
  - - - Factors affecting
        rate of transpiration
        
        Light intensity
        
        The stomata where water evaporates out of from the leaf
        makes the stoma open meaning water can evaporate out
        meaning rate if transpiration is greater. This is as light is needed for water to be allowed into the guard cell as the light triggers a reaction in the guard cell that highers the concentration inside it making possible for the water to enter the cells through osmosis. When water goes into the cell the guard cells open creating a stoma as the guard cells have an inner cell wall that is thickened with extra cellulose. So when water enters the guard cells the inner wall is resistant to the increase of volume so the cell bends in an asymmetrical manner. See notes for photo.
        
        Also effects temperature as more sunlight
        means hotter
        
        Temperature
        
        Hotter temperature means more evaporation
        
        As transpiration is just
        water diffusing out of the plant (this is basically evaporation)
        and heat is a factor of diffusion (water particles diffuse faster because of increase of heat meaning more kinetic energy) meaning the water will evaporate out of the plant quicker increasing the rate of diffusion.
        
        Humidity
        
        The air outside the stoma is saturated with
        water vapour when it is humid. This means the concentration
        gradient is shallower as there is a much closer level of concentration outside the plant to in the plant. This slows down the rate of diffusion so slows down the rate of transpiration.
        
        Wind speed
        
        If there is lots of wind
        the wind can blow away the
        water vapour outside the stoma when it is humid
        increasing the rate of diffusion.