2.1.5 - Diffusion

Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration

• Passive process • It will continue until there is a concentration equilibrium between the two areas • Diffusion happens because the particles have kinetic energy • Movement is random and an unequal distribution of particles eventually becomes an equal distribution

• Temperature - Concentration difference

• As you increase temperature, particles have more kinetic energy and they move more • This increase the rate of diffusion

• As you increase the concentration difference, the greater the net movement of particles • This increases the rate of diffusion

• Simple diffusion - Absorbed directly across the membrane - Facilitated diffusion - Nutrients need a protein channel or carrier protein to transport them

• Steroid hormone • Oxygen • Carbon Dioxide

• Glucose • Protein • Lipid

• Polar molecules and ions - Membranes contain channel proteins through which polar molecules and ions can pass

• Temperature • Conc gradient • Membrane SA • Membrane thickness • No.of channel proteins

Active transport is the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration • Requires energy(supplied by ATP) • Requires carrier proteins

• Molecule bonds to receptor • ATP binds to carrier proteins - ATP hydrolysed to ADP and phosphate • Binding of phosphate to carrier protein causes the protein to change shape • Molecule released to inside of the cell • Phosphate molecule released from carrier protein and recombined with ADP to form ATP • Carrier protein returns to its original shape