1. Cells Maintaining Homeostasis
Cell Transport
Cells Maintaining Homeostasis

3. Cell Membrane
Cell membranes control movement of materials in and out of cells.
They are composed of a double layer of lipid molecules with proteins embedded in the lipid bilayer.

4. Some proteins go part way in, others completely penetrate
Some proteins go part way in, others completely penetrate. The lipids are fluid and the proteins can move about. - fluid mosaic model

5. Brownian Movement

6. Passive Transport no energy used
Molecules move from areas of high concentration to areas of lower concentration
With the concentration gradient
Examples:
Diffusion
Osmosis
Facilitated Diffusion

8. Diffusion Substances move from higher to lower areas of concentrations
Example:
O2 and CO2

9. Diffusion stops when molecules are evenly spread out - equilibrium.
Diffusion is one of the major ways materials move in and out of cells.

10. Diffusion of Oxygen into a Cell9
Diffusion of Oxygen into a Cell
The concentration of
oxygen molecules is
greater outside the cell than inside
So the oxygen molecules
diffuse into the cell

11. Why do we use the term selectively permeable when describing the cell membrane?

13. Selectively permeable = selecting what penetrates

14. 1
Osmosis

15. Water and other small molecules that do not dissolve in lipids diffuse through openings formed by proteins that go through the entire membrane.
Diffusion of water through a membrane is called osmosis.

16. Osmosis
Since water makes up % of a living cell, its movement in and out is of vital importance.
The cell has no control over osmosis. Osmosis will end when equilibrium is reached.
The water concentration is determined by the concentration of solutes in the water.

19. isotonic solution concentration of solutes equal in and out of cell
iso = same

20. hypertonic solution concentration of solutes outside is higher
less water, more solutes
ex: saltwater
hyper = above

21. What is the effect of hypotonic solutions on cells?

23. Cells in hypotonic solutions take in water.
When cells are put in distilled water and burst due to cytolysis the membranes and contents can be separated by a centrifuge for detailed study.

24. What is the effect of hypertonic solutions on cells?

26. Cells in hypertonic solutions lose water
Cells in hypertonic solutions lose water. This causes cells to shrink - plasmolysis.
If humans drink seawater, their cells lose more water than they take in.
crenate = plasmolysis

27. Normal
Plasmolysis
Cytolysis

28. Since osmosis and diffusion take place without any use of energy by the cell, they are called forms of passive transport.