DIFFUSION&

OSMOSIS

Cell membranes are permeable (having pores

or openings) to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

Cell Membranes

MembraneComposition

Lipids

Proteins

Question:How are the materialsarranged?

Plasma membrane

Question

How do materials get acrossa cell's membrane?

•Passive Transport

•Active Transport

Passive Transport

Movement acrossmembranes that does NOTrequire cellular energy.

DIFFUSION

Molecules move from areas of higher

concentrations to areas of lower concentrations

Equilibrium

When the concentration isequal on both sides.

There is no net movement ofmaterials.

Factors that EffectDiffusion

1. Concentration

2. Temperature

3. Pressure

4. Particle size

5. Mixing

Osmosis: the movement of water molecules from an area of high concentration to an area of low concentration.

OSMOSIS

Tonicity

The concentration of waterrelative to a cell.1. Isotonic (same)

2. Hypotonic (below)

3. Hypertonic (above)

Isotonic : contains the same concentration inside & outside the cell. Water diffuses into & out of cell at the same rate.

Isotonic

Hypotonic contains a low concentration)The water diffuses into the cell, causing the cell to swell and possibly explode.

Hypotonic

Hypertonic : contains a high concentration The water diffuses out of the cell, causing the cell to shrivel.

Hypertonic

Active Transport

Movement acrossmembranes that DOESrequire cellular energy.

Forming vesicles

Question?

How does the cell membrane know what to let in and what to let out?

SELECTIVE PERMEABILITY

SELECTIVE PERMEABILITY

Summary

Know membrane structure.

Be able to discuss thevarious methods by whichcells move materials throughmembranes.

Be able to solve problems inosmosis.

You should know & be able to explain the following points:

•Diffusion•Osmosis

•Passive & Active

Transport

•Selective Permeability

•Membrane structure