Biology - Unit 3: Movement into and out of cells

what is the role of water?

a solvent in organisms in processes such as digestion, transport and excretion

where does the energy for diffusion and osmosis come from?

the kinetic energy of random movement of molecules and ions

what is diffusion?

the net movement of molecules or ions from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement

what are the factors that influence diffusion?

• surface area

• temperature

• concentration gradient

• distance

how does surface area affect the rate of diffusion?

as the surface area increases, so does the rate of diffusion as there is more space for the particles to move through

how does temperature affect the rate of diffusion?

as the temperature increases, so does the diffusion rate as the particles have more kinetic energy and move faster

how does the concentration gradient affect the rate of diffusion?

the greater the concentration gradient, the faster the rate of diffusion

how does the diffusion distance affect the rate of diffusion?

the larger the diffusion distance, the slower the rate of diffusion as the particles have further to move

what is osmosis?

the net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane

how are plants supported?

by the pressure of water inside the cells pressing outwards on the cell wall

what happens if you put an animal cell in a hypotonic/dilute solution?

there is a net movement of water into the cell which causes the animal cell to burst

what happens if you put a plant cell in a hypotonic/dilute solution

there is a net movement of water into the cell which causes the plant cell to become turgid

what happens if you put an animal cell in a hypertonic/saturated solution?

there is a net movement of water out of the cell which causes the animal cell to crenate

what happens if you put a plant cell in a hypertonic/saturated solution?

there is a net movement of water out of the cell which causes the plant cell to plasmolyse

what is active transport?

the movement of molecules or ions into or out of a cell through the cell membrane, from a region of their lower concentration to a region of their higher concentration against a concentration gradient, using energy released during respiration

what is the importance of active transport in plants?

ion uptake by root hair cells

what is the importance of active transport in the uptake of ions by the root hair cells

• plants take up ions from the soil via root hair cells

• the concentration of ions in the root hair cell is greater than the concentration of ions in the soil

• energy from respiration is therefore used to transport ions into the cell against the concentration gradient