Osmosis and diffusion

1. Give an example, in your own words, of diffusion from your own experience. Try to use a completely different example from those put forward in the session.

2. Give a physiological example of osmosis in the human body.

3. Answer the following statements as true or false.

(a) For diffusion to occur the temperature must be greater than absolute zero.

(b) For diffusion to occur the temperature must be above zero degrees centigrade.

(c) Diffusion does not occur in solids.

(d) Diffusion can only occur if there is a semi-permeable membrane in the fluids.

(e) Without diffusion human life would be totally impossible.

4. Answer the following statements as true or false.

(a) Osmosis can only occur via a semi-permeable membrane.

(b) In osmosis water moves from an area of high solute concentration to an area

of low solute concentration.

(c) In osmosis water moves from an area of low solute concentration to one of

high solute concentration.

(d) Osmotic properties of a fluid would need to be considered in deciding on an

appropriate intravenous fluid replacement.

5. Explain why red blood cells expand if placed in a medium of pure water.

6. Describe with a basic explanation, what happens to red blood cells when placed in a 0.9% solution of sodium chloride.

Osmosis

1. Draw an arrow to indicate the direction of fluid flow through the semi- permeable membrane.

2. What is the name given to this process?

3. Draw on the fluid levels you would expect to find after 30 minutes.

4. Why will the levels stop changing after a short time?

5. What would you expect if the saline were 0.9% and not 5%?

6. Give two examples of the occurrence of this process in normal physiology.

7. What other processes are used in physiology to move substances across membranes?

Osmosis

The passage of pure solvent across a semi-permeable membrane under the influence of osmotic pressure.

or

Osmosis is diffusion (usually of water) acros a semi-permeable membrane.

remember

Osmosis "waters down"

Diffusion

The process whereby gases and liquids of different concentrations intermingle when brought into contact, until their concentrations are equal throughout.