When particles spread out from a high concentration, to a low concentration.
This happens in the lungs (alveoli) when carbon dioxide is taken out of the body, and oxygen is taken in. The alveoli is good for diffusion because it has;
A good blood supply
Moist lining
Large surface area.
It also happens in plant cells when water is taken up through the root hairs. The root hair cell has;
A large surface area
Contains a vacuole to help absorb water.
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Osmosis
The movement of water molecules from an area of high concentration to an area of low concentration.
If you have a solution of water and a sugar solution;
The water will diffuse into the sugar solution, but the sugar particles are too large to pass through the partially mermeable membrane.
After time, the sugar solution will contain more water than it has before the osmosis began.
Finally, equillibrium, equal amounts of water flowing in each direction.
Osmosis also makes plants swell up and become turgid (full of water, swollen).
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Active Transport
The movement of molecules against the concentration gradient, (from low to high concentration).
When roots hairs take up minerals from the soil, they use active transport. (Diffusion takes up water from the soil, so don't get them confused!)
Active transport occurs when the glucose, amino acids, fatty acids etc.. in the gut are taken into the blood.
Active transport occurs in the kidneys when the water and ions are reabsorbed back into the blood.
good notes! just to add on the first slide... other adaptations of the alveoli include: thin walls to make diffusion easier, spherical shape to give a relatively large surface area :) :)
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