AQA GCSE Further Biology - Exchange Of Materials (1.1-1.9)

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B3 - 1.1 

- Osmosis is the diffusion of water.
- Water diffuses from a dilute solution (high water concentration) to a more concentrated solution (low water concentration) through a partially permeable membrane.
- Water moves into or out of cells by osmosis through the cell membrane.
- The moevement is random and requires no energy from the cell.

B3 - 1.2
Active Transport 

- Active Transport allows cells to take in substances agaisnt a concentration gradient.
- Active transport uses energy from respiration.
- Ions from dilute solutions and other substances such as sugar can be absorbed by active transport.

B3 - 1.3 
The Sports Drink Dilemma 

- Most soft drinks contain : 
*water to replace water lost in sweating
*sugar to replace sugar used for energy releaase in exercise
*mineral ions to replace those lost in sweat
- For normal levels of exercise, water is likely to be as effective as a sports drink.
- Sweat contains water and mineral ions.
- If you swear excessively, your ion cells may become dehydrated.
- Sports drinks are solutions of sugar and mineral ions. The water helps to rehydrate body cells.
- The drinks are designed to help balance the concentration of body fluids and the concentrations inside cells. If the drinks concentration matches the body fluids the solution is called isotonic.

B3 - 1.4
Excahnging Materials - The Lungs 

- Large organisms need exchange surfaces. 
- Exchange surfaces have features to make them more efficient.
- The lungs are adapted to be an efficient exchange surface.
- Efficient exchange surfaces have a large surface area, thin walls or short diffusion paths and an efficient transport system - the blood supply in animals.
- The lungs contain the gaseous excahgne surface. The surface area of the lungs is increased by the alveoli (airsacs).
- Alveoli have thin walls, a large surface area and good gradient.
- Oxygen diffused into the many capillaries surrounding the alveoli and carbon dioxide diffuses back out into the lings to be breathed out.

B3 - 1.5
Ventilating The Lungs 

- The breathing system is designed to move air in and out of the lungs. 
- Ventilation occurs due to changes of pressure inside the chest.
- The lungs are situated in the thorax, inside the


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