movement in and out of cells

igcse bio

what is diffusion?

diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration

what is net movement?

is the movement of all the particles huddled together as a group

what other material can diffusion take place through?

• partially permeable (only some molecules can diffuse through) like cell membrane

• molecules like water, glucose, amino acids

• molecules like proteins and starch cant diffuse through because they’re too big

what progress is diffusion?

diffusion is a passive progress: doesn’t require any energy from the cell

what are the 3 factors that affect the rate of diffusion?

1. concentration gradient

2. temperature

3. surface area

explain the factor concentration gradient

the difference in concentration between 2 places

larger the concentration gradient —> higher the rate of diffusion

explain the factor temperature

higher the temperature, it gives the particles more energy (move around faster, diffuse more quickly overall)

higher temp —> higher rate of diffusion

explain the factor surface area

larger surface area —> higher rate of diffusion

what is osmosis?

• a special case of diffusion

• is a diffusion of water molecules (H2O)

• is the movement of water molecules across a partially permeable membrane. from a region of higher water concentration, to a region of lower water concentration

what does cell wall prevent it from?

it prevents it from bursting (turgid)

what does flaccid mean?

when the concentration outside of the cell is lower than the inside which will cause too much water to leave the cell and become dehydrated