1. Unit 6
Cell Transport
Part 1

2. Cell Membrane/Plasma Membrane
Separates the cell from the non-living outside environment
Without a cell membrane there could be no cell
Performs two functions:
It separates the cell from its outside environment
It enables communication and movement of the materials between the cell and its environment

3. Transport across the Cell Membrane
Selective permeability – cell membrane allows some substances to pass through but keeps others out (Border control, Customs, Airport security)
So the cell membrane is selectively permeable or semi-permeable
Cell membrane can also control if the transport of these molecule is fast or slow

5. Fluid Mosaic Model Cell membranes are made up of lipids
Protein molecules float within the lipid molecules of the cell membrane
This arrangement of molecules in constant motion is called the fluid mosaic model

6. The role of Proteins
Two Types: Transport proteins and Receptor proteins
Transport proteins: Enable much of the transport or movement of materials across the cell membrane. Sometimes called carrier
proteins.
Receptor proteins: function as receptor molecules – receive signals from the outside and transmit the signal to the inside of the cell enabling communication between cells

8. Semi-permeable –materials that can pass and materials that can't

9. Passive Transport Molecules are always in motion
They naturally move from high to low concentrations
The difference in concentration between two areas is called a concentration gradient

10. Solute A substance that is being dissolved to make a solution
In the case of sugar and water it is the sugar because it is being dissolved in the water

11. Solvent
A liquid that is dissolving another substance to make a solution
In the case of sugar and water it is the water because the water is dissolving the sugar

12. Diffusion
Diffusion – The random movement of molecules down the gradient or from high to low concentration
Example: Perfume

13. How Does Diffusion Work?
Pores in the cell membrane allow these materials to pass thru
Diffusion happens automatically if the membrane is permeable to that molecule and there is a difference in concentration on either side
This is called passive transport because no energy is used by the cell to move these molecules

15. Hypertonic Solution Higher concentration of solutes outside the cell
Higher concentration of water inside the cell
Water moves out of cell and cell shrinks

16. Hypotonic Solution Higher concentration of solutes inside the cell
Higher concentration of water outside the cell
Water moves into the cell and cell expands

17. How Diffusion Works Continued. . .
They continue to move from high amounts to low amounts until there is an even amount of each side this is called equilibrium or isotonic

18. Equilibrium (Isotonic)
Diffusion will continue until there is the same concentration of water and solute molecules on each side of the cell this is called isotonic

19. Function of Diffusion in the Cell
This is how cells get food and oxygen

20. Osmosis Osmosis – movement of water across cell membrane.
- The movement of water continues until there is the same amount of water on both sides of the membrane this is called equilibrium.

22. Why Does Osmosis Happen in Cells?
Cells are surrounded by water so there
must be the same amount of water inside as outside the cell.

23. Question Worth Homework Pass: What happens to a plant when its cells lose too much water?
Answer: Plants wilt! Plant cell membrane pull away from cell walls in a process called plasmolysis