- osmosis is the diffusion of water
- water diffuses from a dilute solution through a partally permeable membrane
- water movies into or out of cells by osmosis through the cell membrane
osmosis refers to the movement of water molecules only
1.2 active transport
- active transport allows cells to take in substances against a concertration gradient.
- active transport uses energy from respiration
- ions, from dilute solution and other substance such as sugur can be absorbed by active transport.
1.3 the sports drink dilemma
- water to replace that lost when sweating
- sugar used to replace what needed for creating energy
- mineral ions for those lost in sweating
water just as effective for normal levels of exersie.
1.4 EXCHANGING MATERIALS- LUNGS
organisms have exchange surfaces (efficient exchange surfaces) : large surface area, thin walls, short diffusion path, efficent transport.
the lungs are adapted to be efficent exchange surface area.; alveoil highly adapeted for this. (thin walls, large surface area, good blood supple)
1.5 VENTILATING THE LUNGS
ventilation happens due to changes of pressurre.
1.6 ARTIFICAL BREATHING AIDS
- RESONS FOR THEM; alveoil damged, tubes narrowed, paralysed.
- IRON LUNG in cyclinderair dran in and out to ceat pressure in vacum. (NEGTIVE PRESURE)
- POSITIVE PRESSURE; bags of air likind to mask force air down trachea.
1.7 EXCHANGE IN GUT
- villi lines the suface of the small intestine and are a very efficient exchange surface.
- there job is to absorb soluble products of digestion by diffusion or active transprt.
they have: large surface are, thin walls, good blood supply.
1.8 EXCHANGE IN PLANTS
- the stommata in plant leaves allow carbon dioxide to diffuse the leaf from the atmosphere
- leaves are flat and thin with internal air spaces to increase the surface area for diffusion of gases
- root hair cells incrase the surface area of the roots.
if the stomata loses to much water they can wilt
- water is lost from leaves by evaporation
- the water vapour escapes the leaf through the stomata when they open to allow carbon dioxide to enter the leaf
- wilting can protect the leaf from excessive water loss.