B3- exchange of materials
- Created by: safia rassool
- Created on: 09-06-16 13:37
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osmosis
- osmosis is the net movement of a substance down a concentration gradient over a partially permeable membrane
- osmosis requires energy from the cell
- only small enough particles can diffuse through the partially permeable membrane
active transport
- active transport allows sells to take substances in against the concentration gradient- from an area of low concentration to high concentration
- this requires more energy created by respiration than osmosis
- cells may sometimes need to absorb substances in short supply and the transport proteins allow this
- cells can aborb ions from dilute substances e.g a root hair cell can absorb nitrates from soil water
- glucose is absorbed by the kidney through active transport
- the transport protein takes the useful molecule and turns into the cell then releases using energy
sports drink dilemma
- when you exercise your muscles respire to create energy for movement- glucose is used in respiration
- when you get hot you sweat to cool down and in your sweat there is mineral ions and water- increased sweating means dehydration
- therefore when exercising you need to replace the stuff thats lost
- sports drinks contain sugar, water and mineral ions designed to rehydrate the body cells
- if a drink concentration matches the body fluid it is isotonic
exchanging materials in the lungs
- large, complex organisms have large surface areas to obtain food and oxygen thats needed
- soluble food is absorbed by the small intestine, oxygen by the lungs and co2 is removed from them
- efficient exchange surface- thin walls for diffusion, large SA and an efficient transport system (circulatory system)
- in the lungs there is a gaseous exhchange surface (exchange of oxygen and co2 between the air in lungs and blood) the surface area is increased by the multiple alveoli which are air sacs
- the lungs are ventilated…
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