diffusion

what does passive mean

• energy comes from natural motion of particles

describe the passive movement of particles

• moving in constant random motion due to kinetic energy

• move in straight lines and act as rigid spheres

• colliding and bouncing

diffusion definition

• net movement of molecules or ions from a high concentration to a low concentration until a dynamic equilibrium is reached

• move down a concentration gradient

what molecule that is small and non polar can pass along the membrane

Oxygen

why do molecules that are charged and polar do not easily pass through membrane?

• hydrophobic nature of fatty acid tails

what is facilitated diffusion

• passive

• relies on kinetic energy

• occurs where there are protein molecules ( protein channels and carrier proteins)

what are protein channels

• form water filled hydrophilic channels across membrane

• allow water soluble ions to pass through

• opens when a particular ion is present ( called aquaforins)

how does the control of the entry and exit of ions occur

• ions bind with the protein allowing it to change shape in a way that one side opens and one side closes

Describe how carrier proteins work

• when a molecule such as glucose is specific to protein and is present, it binds with the protein

• This causes it to change shape so that the molecule is released for no energy required

• Particles move from high to low concentration with their own kinetic energy