Exchange Of Materials Unit 3 Revision Flashcards
Osmosis in living things
Differences in the concentrations of solutions inside and outside a cell cause water to move into or out of the cell by osmosis
What is active transport
The movement of molecules against the concentration gradient . This uses a transport protein, and requires energy, the energy comes from cellular respiration.
Where does active transport occur in humans
Sugar such as glucose is always actively absorbed out of your gut and kidney tubules into your blood. This is often done against a large concentration gradient.
After a meal you might have a large amount of glucose and mineral ions in your blood, and a smaller amount in your small intestine so active transport will be used to absorb food.
Where does gas exchange take place in the lungs
The job of the lungs is to transfer oxygen to the blood and remove waste carbon dioxide from it.
To do this the lungs contain millions of little air sacs called alveoli where gas exchange takes place
How are alveoli specialised for gas exchange
Alveoli are specialised to maximise the diffusion of oxygen and carbon dioxide they have:
1) a large surface area (about 75m2 in humans)
2) a moist lining for dissolving gases.
3) very thin walls (short path for diffusion)
4) a good blood supply (maintaining concentration gradient.)
How are villi specialised for absorption of substances.
The inside of the small intestine is covered in finger like projections called villi
They increase the surface area in a big way so that digested food is absorbed much quicker into the blood.
So they have a large surface area for diffusion
They are 1 cell thick so there is a short path for diffusion.
A very good blood supply maintaining a steep concentration gradient.
What is Osmosis
Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
Adaptions for exchanging materials
- having a large surface area
- being thin which provides a short diffusion path
- having an efficient blood supply, in animals this moves the diffusing substances away and maintains a concentration diffusion gradient.
*being well ventilated to make gaseous exchange more efficient by maintaining steep concentration gradients.
Exchanging materials in the lungs / how are they adapted for efficient gas exchange.
1) Air into lungs relatively high in 02 low in C02
2) air in alveolus oxygen moves into the blood C02 moves out of the blood.
3) air out of the lungs relatively high in C02 low in 02
As a result the gas exchange takes place along the steepest concentration gradient possible. This makes the gas exchange rapid and effective. The layer of cells between the air in the lungs and the blood in the capillaries is also very thin. This allows diffusion to take place over the shortest possible distance.
