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Revison Homework - Week 3 (Diffusion (Happens in soloutions and gases, The…
Revison Homework - Week 3
Diffusion
Happens in soloutions and gases
The larger the concentration gradient, the faster the diffusion
Higher temperature = faster diffusion
Dissolved substances move in and out of cells via diffusion
Only small particles fit through, e.g: oxygen and amino acids. Big particles such as starch cannot.
Particles move through the cell membrane from high to low concentration.
The larger the surface area, the quicker the diffusion
It is a "passive" process, as it requires no energy
Osmosis
From high to low concentration
water molecules pass through both ways, as water moves randomly
However, because there are more molecules on one side, there is a steady net flow of water
Movement of water molecules across a partially permeable membrane
Type of diffusion
You can observe osmosis by doing an experiment on plant tissue:
link
Active Transport
When substances travel against the concentration gradient, therefore it is an "active" process, as it requires energy
Used in root hair cells to absorb minerals, as the concentration inside the cell is usually greater then in the soil
Happens in root hair cells, the gut and the kidneys
Happens in the gut to transport glucose into the blood, as there is more glucose in the blood
This is when substances travel against the concentration gradient, from a high to low concentration
Exchange Surfaces
Alveoli
Used for gaseous exchange in the lungs
Moist lining
Thin walls
Good blood supply
Enormous surface area
Villi
Line the small intestine
Very good blood supply
Large surface area
Single layer of surface cells
They have many adaptions:
Large surface area so more diffusion can occur
Good blood supply for animals
Thin membrane, so substances only have a short distance to diffuse
Well ventilated for plants
Leaves
The structure makes them very good at diffusion
Stomata controlled by guard cells which close if the plant is losing too much water
Flattened shape increases surface area
Stomata to let CO2 diffuse in, Water and O2 out
Walls inside the leaf form another exchange surface, increasing surface area
Gills
Exchange surface in fish
Gills are made of filaments, which increase surface area
Filaments covered in lamellae, increasing surface area
Water enters mouth and passes out through the gills
Blood flows in the opposite direction to the water, maintaining a large concentration gradient.
Thin surface layer
Ben Macken 10Y
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