Biology B3

Active Transport.

• The movement of substances in and out of cells from Low to a High concentration.
• Energy is needed for Active Transport
• Active transport is against a concentration gradient.

Diffusion

• The movement of substances in and out of cells from High to a Low concentration.
• Energy is NOT needed for Diffusion.
• Diffusion is ALONG a concentration gradient.
• 

Osmosis:

• Same as Diffusion
• Water diffuses from a concentrated area to a less concentrated through a semi-permeable membrane.

Arteries:

Veins:

• carry deoxgenated blood back to the heart
• don't have a pulse - have valves to prevent back-flow of blood
• have thin walls - large lumen (hole inside)

Capillary :

• narrow walls a single cell thick so oxygen+glucose can pass from blood into cells easily - diffusion + carbon dioxide can pass from cells into blood
• tiny vessel with narrow lumen
• take blood from arteries to body cells to veins
• walls

• Carry oxygenated blood away from the heart
• Arteries stretch as blood is forced through them they then return to their original shape
• Arteries have thick walls a small lumen and a thick layer of muscle and elastic fibres

Human Kidney

The kidneys filters the blood, removing the substances which the body does not need. The kidney first filters all of the blood and then reabsorbs substances which it body needs.

Dialysis:

Dialysis restores the concentration of substances in the blood back to normal, but needs to be carried out regularly. If your kidneys failed, then you'd die, but through a dialysis machine you'd survive. The machine involves long sessions connected to a machine which is expensive and involves a controlled diet.

•Kidney transplants: • A donor who has the same blood type and same tissue match is needed . The body is likely to to reject a new kidney, to stop this the patient must take drugs to suppress the immune system, be kept in a sterile environment to prevent him/her from falling ill for they have a weak immune system because of the drugs, the recipient's bone marrow has to be treated with radiation to stop it from producing white blood cells.