Exchange & Transport

Why do organisms need special exchange surfaces?

They need special exchange surfaces to live because all living cells need ceratin substances to keep them alive:

• Oxygen-for aerobic respiration
• Glucose-for energy
• Proteins-for growth and repair  
• Fats- for making membranes and to be a store of energy
• water
• minerals to maintain water potential

G  LUCOSE

O  OXYGEN

M  INERALS

P  ROTEINS

F ATS

W ATER

What do exchange surfaces look like?

• Large surface area to provide more space for molecules to pass through.
• Thin barrier to reduce diffusion distance.
• Fresh supply of molecules on one side to keep concentration high
• removal of required molecules on the other side to keep the concentration low.

( last 3 important for a steep diffusion gradient)

Examples of specialised exchange surfaces:

• Small intestine where nutrients are absorbed

• liver where sugars in the blood are adjusted
• root hairs of plant where water and minerals are absorbed

• hypae of fungi where nutrients are absorbed