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Specialised Cells
· Palisade leaf cells are adapted for photosynthesis.
Packed with chloroplasts.
Tall shape means a large surface area.
· Guard cells adapted to open and close pores.
Kidney shape opens and closes stomata.
Guard cells get rid of excess water.
· Red blood cells adapted to carry oxygen.
Concave shape gives a big surface area.
Packed with haemoglobin ­ pigment that absorbs oxygen.
· Sperm and egg cells specialised for reproduction.
Tail on sperm helps it "swim".
Lots of mitochondria.…read more

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· Diffusion is passive movement of particles from an area of
high concentration to an area of low concentration.
· Diffusion happens in liquids and gases.
· Bigger concentration difference, faster diffusion rate.
· Cell membranes hold cell together.
· Substances can move in and out of cells by diffusion and
· Rate of diffusion depends on:
­ Distance
­ Concentration difference (gradient)
­ Surface area.…read more

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· Osmosis is a "special case" of diffusion.
· Osmosis is movement of water molecules across a partially
permeable membrane from a region of high concentration to an
area of low concentration.
· Partially permeable membrane is one with small holes in it.
· Water molecules pass both ways.
· More on one side that on other side.
· Water moves in and out of cells by osmosis.
· Tissue fluid surrounds cells in body.
· Tissue fluids have water concentration.
· If cell is short of water, solution will become concentrated.
· The more water in a cell, the more dilute the solution is inside.…read more

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Carbon dioxide + water glucose + oxygen
· Photosynthesis produces glucose using sunlight.
· Photosynthesis is food making process in plants.
· Happens in leaves. Inside the chloroplasts.
· Four things needed for photosynthesis:
­ Light: usually from the sun
­ Chlorophyll: green substance found in chloroplasts.
­ Carbon dioxide: enters leaf from air.
­ Water: comes from soil up roots and stem into leaf.…read more

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The Rate of Photosynthesis (1)
· The limiting factor depends on the conditions.
· Any of three factors can be limiting factor.
· Environmental conditions select limiting factor.
· At night it's light.
· In winter it's temperature.
· If warm enough and bright enough, CO2 is limiting.
· Not enough light slows down photosynthesis rate.
Light provides energy needed for photosynthesis.
As light level is raised, the rate of photosynthesis
increases steadily.…read more

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