GCSE AQA Biology 3 Movement in & out of Cells

Lilac Potato
Mind Map by Lilac Potato, updated more than 1 year ago


A mind map showing information about osmosis, gas & solute exchange, diffusion through cell membranes (alveoli & villi) and active transport.

Resource summary

GCSE AQA Biology 3 Movement in & out of Cells
1 Osmosis


  • Type of diffusion
1.1 Definition: the movement of water from an area of high concentration to an area of low concentration through a partially permeable membrane
1.1.1 Partially permeable membrane has very small holes in it - only tiny molecules like water can pass through
1.2 Water molecules pass both ways through the membrane during osmosis - molecules move about randomly
1.2.1 More on one side - net flow of water to area of low concentration Stronger sugar solution gets more dilute - water acts like it's trying to even up the concentration on either side
1.3 Tissue fluid surrounds cells in body - water with oxygen, glucose etc
1.3.1 Will usually have different concentration to fluid inside cell - water will move in or out of the cell If cell is short of water it will be concentrated - solution outside is dilute, water will move in by osmosis If cell has lots of water, will be more dilute - water will be drawn out of cell by osmosis
2 Gas & solute exchange
2.1 Substances move by diffusion, osmosis & active transport
2.1.1 Life processes need gases/other dissolved substances & waste substances also need to move out of cells Have to move through exchange surfaces which are adapted by: Being thin - shorter diffusion distance Having a large SA - lots of substance can diffuse at once Having lots of blood vessels (animals) - to get stuff in/out of blood Being ventilated (animals) - air moves in/out
2.2 Structure of leaves lets gases diffuse in/out
2.2.1 Carbon dioxide diffuses into air spaces in leaf, then into cells Underneath of leaf is an exchange surface - covered in stomata which carbon dioxide diffuses in through Oxygen & water vapour diffuse out through stomata Size of stomata controlled by guard cells - close if plant is losing water faster than getting from roots
2.2.2 Flattened shape of leaf increases area of exchange surface Walls of cells inside leaf = another exchange surface - air spaces inside leaf increase area of surface Water vapour evaporates from cells inside leaf, escapes by diffusion (lots inside, less outside) = evaporation quickest in hot, dry, windy conditions
3 Diffusion through cell membranes
3.1 Gas exchange happens in the lungs - lungs transfer oxygen to RBC & remove waste carbon dioxide from plasma
3.1.1 Lungs contain aveoli where gas exchange takes place Adapted to maximise diffusion of oxygen & carbon dioxide by having: Large SA Moist lining - for dissolving gases Thin walls Good blood supply
3.2 Small intestine is covered in villi - they increase the surface area so digested food is absorbed quickly into the blood
3.2.1 Adapted by having: Single layer of surface cells Good blood supply to assist quick absoption
4 Active transport
4.1 Definition: The process that allows substances to be absorbed against a concentration gradient (from low to high concentration) which requires energy (from respiration)
4.2 Root hairs - specialised to absorb water & minerals
4.2.1 Cells on surface of plant roots grow into hairs which increase SA The concentration of minerals is usually higher in the root hair cell - active transport has to happen
4.3 Used in gut - when there's low concentration of nutrients in gut but high in blood
4.3.1 Has to absorb against concentration gradient
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