Exchange of materials

1.1 osmosis

• 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

they contan;

• 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.

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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

1.9 TRANSPIRATION

• 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.