Transport Avross Membranes

The two components which make up the cell membrane are ● Phospholipids ● Proteins

This means that some substances freely cross the cell membrane in or out of the cell, whilst other substances cannot.

Diffusion is the movement of molecules down a concentration gradient from a high to a low concentration. Thus is passive process and does not require energy

Substances such as glucose and oxygen move into a cell by diffusion. Substances such as carbon dioxide move out of a cell by diffusion

Osmosis is the movement of water molecules down a concentration gradient from a higher water concentration to a lower water concentration. Passive

If blood is under high water concentration it will burst If it’s same concentration nothing will happen If it is lower concentration it will shrink

Because it does nit have a cell wall

If plant is under high water concentration it will become turgid If it’s same solution concentration nothing will happen If it is lower water concentration it will plasmolise

Due to the cell wall

Active transport requires energy. It is the movement of molecules and ions against the concentration gradient from a low concentration to a high concentration