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movement of molecules p14-23 (exchanging materials (the surface are to…
movement of molecules p14-23
diffusion
diffusion is the speeding out of the particle of gas or any outer substance in solution this results in the net movement of particles the net moment is form an higher concentration to a area of lower concentration of the particle
rates of diffusion
if there is a big difference in concentration between two areas diffusion will take place quickly however if there is only a small difference in the concentration diffusion will happen quite slowly
diffusion in living organisms
dissolved substances move into and out of your cells by diffusion across a call membrane theses include simple sugars such as glucose gassed such as oxygen and carbon dioxide
osmosis in plants
plants rely on osmosis to support their stems and leaves water moves into the plant by osmosis
osmosis
a dilute solution of sugar contains a high concentration of water and a low concentration of sugar
a concentrated sugar solution contains a relatively low concentration of water and a high concentration of sugar
definition
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.
active transport
definition
the movement of ions or molecules across a cell membrane into a region of higher concentration(against the concentration gradient), assisted by enzymes and requiring energy.
active transport uses energy from food in respiration to provide energy
active transport allows plant root hair cells to absorb mineral ions required for healthy growth from very dilute solutions in the soil
active transport enables sugar molecules used in cell respiration to be absorbed from lower concentrations in the gut into the blood where the concentration of sugar is higher
exchanging materials
the surface are to volume ratio is very important in biology
to wor out the suface area to volue ratio you work out the surface area and the volume of the shape for example
a cube is 1 cm by 1 cm by 1 cm its suface area to volume is
SA : V ratio = 6:1
single-celled organisms have a relatively large surface area to volume ratio so all necessary exchanges with the environment take place over this surface
in multi cellular organisms many organs are specialised with effective exchange surfaces
exchange surfaces usually have a large surface area and thin walls which give short distances in animals exchange surfaces will have am efficient blood supply or for gaseous exchange be ventilated
