5th year Biology- Diffusion and Osmosis

What is diffusion?

Movement of molecules from high to low concentration

What is a selectively permeable membrane? Give an example.

allows some but not all molecules to pass through (visking tubing, cell membranes)

Diffusion is a _____ process

passive

Examples of diffusion

co2 diffusing into a leaf o2 diffusing out

What is osmosis?

diffusion of water across a selectively permeable membrane

animal cells in a solution the same concentration as their cytoplasm

isotonic (water moves in and out at the same rate)

Animal cells in a more concentrated solution

hypertonic (the cell shrivels up - crenation)

Animal cells in less concentrated solution

hypotonic (the cell bursts - haemolyse)

cell walls are ________

fully permeable

Plant cells in less concentrated solution

swell up and become turgid

Plant cells in a more concentrated solution

shrivel (plasmolysis)

Plant cells in an equally concentrated solution

stay the same

the vacuole contains ________

cell sap

Turgor

pressure of the cytoplasm and vacuole against the cell wall

osmosis and food preservation

kills micro-organisms to stop them decaying foods (salting meats)

active transport

molecules (eg potassium) moving against the concentration gradient.

What does active transport require?

energy from the breakdown of ATP