1. Cells and Their Environment
Cell Transport
Cells and Their Environment

3. Brownian Movement
Molecules - whether in living systems or not are governed by physical laws of movement.
Molecules are always in motion - even in solids (fixed areas).
In liquids and gases - random motions called Brownian movement.

4. 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.

5. 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

6. Diffusion
Diffusion is the process by which molecules of a substance move from higher to lower areas of concentrations due to the random motions of Brownian movement.

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

10. Concentration Gradient
The movement from high to low concentrations is called with the concentration gradient.
A diffusion gradient

11. The higher the concentration - the faster the diffusion.
The higher the temperature - the faster the diffusion. (molecules are moving faster)
The higher the pressure - the faster the diffusion. (more chances of collisions)

12. 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

13. Oxygen and carbon dioxide can dissolve in lipids and pass right through the membrane.

15. 1
Osmosis

16. 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.

17. 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. hypotonic solution concentration of solutes outside is lower
more water, less solutes
ex: distilled water
hypo = under

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

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

24. Cells in hypotonic solutions take in water.
In plant cells, the cell wall can take the increased pressure and turgor results.
The plant cells are stiff.

26. Animal cells can use excretion or contractile vacuoles (found in unicellular organisms) to keep from bursting - cytolysis.
cyte = cell
- lysis = to burst

27. 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.

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

30. Cells in hypertonic solutions lose water
Cells in hypertonic solutions lose water. This causes cells to shrink - plasmolysis.

34. If humans drink seawater, their cells lose more water than they take in.

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

44. The End