Osmosis

Goal: I will be able to explain the

process of diffusion and osmosis as they

relate to cells.

Imagine

Have you ever gone to the ‘fridge’ and

notice the celery has gone limp?

What happened?

As the celery loses water

it becomes limp.

Water molecules are so small they travel

across cell membranes by diffusion.

When water diffuses across a selectively

permeable membrane it is called

Osmosis

Cells and concentrated

solutions

The movement of water in and out of

cells is vital to living things and is driven

by imbalances in concentrations.

Ideally solute concentration outside the

cell is equal to that inside the cell.

Usually in cells, sugars and salts are

common solutes, and water is the solvent

Isotonic Solutions: contain the same

concentration of solute as in another

solution (e.g. the cell's cytoplasm).

When a cell is placed in an isotonic

solution, the water diffuses into and out

of the cell at the same rate.

Hypotonic Solutions: contains a low concentration of solute relative to another solution (e.g. the cell's cytoplasm).

https://www.youtube.com/watch?v=OYoaLzobQmk

https://www.youtube.com/wa

tch?v=gWkcFU-hHUk

Hypertonic Solutions: contain a high

concentration of solute relative to another

solution (e.g. the cell's cytoplasm).

https://www.youtube.com/watch?v=lzDlGl3

b4is&feature=related

Question 1: Give an example of diffusion.

Question 2: How are osmosis and diffusion

different? How are they the same

Question 3: What determines the direction

of water movement into or out of cells?