BIOLOGY 4.1

charl.mallon
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GCSE Biology Mind Map on BIOLOGY 4.1, created by charl.mallon on 06/03/2014.

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charl.mallon
Created by charl.mallon over 5 years ago
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BIOLOGY 4.1
1 OSMOSIS
1.1 The net movement of water molecules across a partially permeable membrane from a region of high concentration of water to a region of low concentration of water
1.1.1 High water conc = dilute
1.1.2 Low water conc = concentrated
1.2 A partially permeable membrane is one with very small holes in it
1.2.1 The water molecules pass both ways through the membrane during osmosis
1.2.1.1 This is because water molecules move about randomly all the time
1.2.2 Small molcules ie water can pass through, bigger ones ie sucrose can't
1.3 Because there are more water molecules on one side than on the other, there's a steady net flow of water into the region with fewer water molecules
1.3.1 This means the concentrated solution gets more dilute - the water acts like it's trying to 'even up' the concentration on either side of the membrane
2 TURGOR PRESSURE
2.1 Turgid = when a plant is well watered, its cells will draw water in by osmosis and become plump and swollen
2.1.1 Turgor pressure: when the contents of the cell push against the inelastic cell wall
2.1.1.1 Flaccid = no water in soil = cells lose water & turgor pressure - plant starts to wilt
2.1.1.1.1 Plasmolysed cell: when really short of water, the cell's cytoplasm starts to shrink & the membrane pulls away from the cell wall.
2.1.1.1.1.1 Doesn't totally lose its shape because of inelastic cell wall
3 ANIMAL VS PLANT
3.1 Animal cells don't have a cell wall
3.2 If an animal cell takes in too much water, it bursts - lysis
3.3 If an animal cell loses too much water it shrivels up - crenation
4 DIFFUSION
4.1 The net movement of particles from high concentration to low concentration
4.2 Liquids & gases
4.3 CELL MEMBRANES: hold the cell together but also let things in and out
4.4 Only very small molecules can diffuse through cell membranes
4.5 Rate depends on:
4.5.1 Surface area: more space for particles to move across
4.5.2 Concentration gradient: substances move more quickly when there is more of a difference - if there are lots more particles on one side, there are more there to move across
4.5.3 Distance: the smaller the distance, the quicker the movement

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