Diffusion, osmosis and active transport

Diffusion

Movement of particles from an area of HIGH CONCENTRATION to that of a LOW CONCENTRATION (‘down the concentration GRADIENT’)

This is PASSIVE as it requires no energy. RATE can be increases by increasing:

Difference in concentration

Surface area

Temperature

Osmosis

Diffusion of water across a SEMI-PERMEABLE MEMBRANE to balance the concentrations of solution inside and outside a cell

Water must move, as larger molecules cannot fit through the holes

Water moves IN if the concentration is higher OUTSIDE

Osmosis Pratical

Weigh and place identical cylinders from same vegetable in sugar solution of varying concentrations

After set time, remove excess water (pat dry) and reweigh, calculate % change in mass = final mass - initial mass/initial mass x 100

Plot % change in mass against concentration. Using the line of best fit , the concentration at 0% change in mass is the same as inside the vegetable

Active Transport

Movement of particles through a membrane via CARRIER PROTEINS

Requires energy and so can move AGAINST the concentration gradient