Notes.

Active transport:
The movement of substances from an area of low to high concentration.
Active transport allows cells to absorb ions from very dilute solutions
It also allows the movement of substances such as sugars and ions from one place to another through the cell membranses.
It takes energy for the system to carry a molecule across a membrane and return it to its original position. This energy comes from cellular respiration. The rate of respiration and te rate of active transport are closely linked.
Osmosis and diffusion depend on a concentration gradient in the right direction to work. Substnaces are moved against a concentration gradient by active transport, which uses energy produced by mitochondria.
THE SPORTS DRINK DILEMMA.
When you exercise, you release energy (by respiration) to make your muscles contract. you sweat to maintain a constant body temp. (sweat contains water and mineral ions).

the more you sweat,the more water and mineral ions you lose. This affects the concentraion of your body fluids. If they become concentrated, water will leave your cells (by osmosis). The cells become dehydrated.

If the water and mineral ions you lose in your sweat aren’t replaced, the miner ion and water balance of your body will be disturbed and your cells will not work as effiently as usual.
Sports drinks are mainly water. They contain sugar (usually glucose). It also contains more mineral ions than most normal soft drinks. It also contains colourings and flavourings.
Evidence to support sports drinks:
-contain a moajority of water so they dilute body fluids (encourages water back into the cells to rehydrate – through osmosis)
-contain salt which raises your ion levels (allowing ions back into your cells by diffusion
-raise the blood sugar level so sugar moves back into your cells by diffusion and active transport.

EXCHANGE MATERIALS – THE LUNGS.