AQA Biology- Cell Biology- Transport in Cells

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What is diffusion?
The movement of particles from a high to a low concentration until they reach equilibrium.
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What factors affect the rate of diffusion?
The concentration gradient- the bigger the difference in concentrations the faster the rare of diffusion. The temperature- the higher the temperature the more energy the particles have. The surface area.
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What is osmosis?
The net movement of water molecules from an area of high to low concentration through a partially permeable membrane until they reach equilibrium.
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Examples of diffusion
Gas exchange in the alveoli. Gas exchange for photosysnthesis. Gas exchange for respiration.
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Examples of osmosis
Absorption of water by plant roots. Re-absorption of water in the kidneys.
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What is active transport?
The movement of particles from a low to a high concentration. This requires energy provided by respiration.
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What is an exchange surface?
A surface where exchange takes place. (Diffusion, osmosis and active transport)
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What factors increase the effectiveness of an exchange surface?
Thin membrane- so substances have a short distance to diffuse (short diffusion pathway). Large surface area- so a lot of substances can diffuse at once. Moist- gas exchange is easier. High concentration gradient
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Why does the villi have a good exchange surface?
Large surface area, further increased by the micro-villi. This membrane wall. Rich blood supply.
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Why do the alveoli have a good exchange surface?
Large surface area. High concentration gradient. Moist. Big capillary network.
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Why do fish have good exchange surfaces?
They are moist. They have gill stacks which are layers of tissue that are 'frilly' so that they have large surface areas so that the oxygen from the water can diffuse in. Thin gills. Rich blood supply. High concentration gradient
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Why do frogs have good exchange surfaces?
TADPOLE. External gills so that oxygen can diffuse. 'Frilly' so that the surface area is increased. Rich blood supply. Moist. FROG. Gills disappear, exchange happens through skin. Slimy, moist. Blow themselves up to increase surface area,skin thinner
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Why do insects have good exchange surfaces?
They have trachioles that are small holes in the skin so that oxygen can get in. They are thin. High surface area. Constant concentration gradient
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Other cards in this set

Card 2

Front

What factors affect the rate of diffusion?

Back

The concentration gradient- the bigger the difference in concentrations the faster the rare of diffusion. The temperature- the higher the temperature the more energy the particles have. The surface area.

Card 3

Front

What is osmosis?

Back

Preview of the front of card 3

Card 4

Front

Examples of diffusion

Back

Preview of the front of card 4

Card 5

Front

Examples of osmosis

Back

Preview of the front of card 5
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