Movement in and out of cells

What is diffusion?

It’s the net movement of molecules from a place of high concentration, to low concentration. Due to their random movement and knetic energy.

How do oxygen and carbon dioxide enter and leave cells?

They enter and leave cells through diffusion in cell membranes, down a concentration gradient.

What speeds up diffusion in the cell?

• Temperature increase

• Concentration increase

• Surface area increase

How can we investigate diffusion increases?

Using pieces of agar jelly

What is osmosis?

The net movement of water through a partially permeable membrane from a region of high water concentration to lower water concentration.

How can we investigate osmosis?

With partially permeable dialysis tubing.

What happens to animal cells when placed in a concentrated solution or pure water?

They burst and shrink.

What happens to plant cells when placed in a concentrated solution or pure water?

They don’t burst, their cell wall stops this from happening.

What is a solution containing lots of water in osmosis terms?

It has high water potential.

What happens when a plant cell experiences changes in concentrations?

• In pure water it takes up water due to osmosis, and becomes turgid, this is because it’s contents exert outwards and put pressure on the wall,

• In concentrated solutions they loose water by osmosis, becomes flaccid and may plasmolyse.

What is active transport?

It’s the movement of cells across a cell membrane, up the concentration gradient, using energy from respiration.

What do protein carriers in cell membranes do?

They change shape to move substances across the cell membrane during active transport.