1. Unit Five: Cell Transport

2. Passive Transport: • One of the main functions of the cell membrane is to keep the cell’s internal conditions relatively constant. • It does this by regulating the movement of molecules.

3. Plasma Membrane: • Recall that the plasma (cell) membrane controls what comes into and out of the cell. • Responsible for maintaining homeostasis. • This means it keeps the proper chemical balance inside the cell. • Water, glucose, amino acids, oxygen, and carbon dioxide are a few examples of things that must be regulated in cells.

4. Plasma Membrane: Phospholipid Bilayer HYDROPHILIC “water” + “loving” Hydro phillic “heads” Hydro phobic “tails” “water” + “fearing” HYDROPHOBIC

5. The Plasma Membrane

6. What else is in the membrane besides phospholipids? • Cholesterol= helps solidify and stabilize the “fluid” membrane. • Carbohydrates =specific pattern on the outer surface of cells for self-recognition. • Proteins= channels for molecules to pass through that otherwise wouldn’t fit.

7. Characteristics of the Membrane • Fluid Mosaic Model: describes how the parts of the membrane are not stuck in place but have the ability to move around. • Semi-permeable: only allows some molecules to pass through the membrane. YES NO Large molecules Polar molecules Charged molecules • Small molecules • Nonpolar molecules

8. Membranes are Semi-Permeable • Semi-Permeable = describes a membrane that only allows SOME molecules to pass.

9. Important Vocabulary: • Concentration Gradient = when the amount of substances (concentration) is different in two places. • Equilibrium = when the amount of substances (concentration) is the SAME in both places.

10. There are TWO types of transport: ACTIVE TRANSPORT: • This does not occur naturally so they cell has to use energy (ATP) to make active transport occur. • Molecules move from a region of LOW concentration to HIGH concentration. • REQUIRES energy.

11. HIGH ATP Passive Active LOW LOW

12. Diffusion: • Diffusion= movement of materials from an area where there is a lot (high concentration) to where there is little (low concentration). • Type of passive transport • Occurs naturally • Does NOT require energy • Due to random motion of molecules

13. Diffusion: • Diffusion is everywhere! • Air passes through glass in your house. • The smell of cookies baking in the kitchen • How your helium balloon deflates • Occurs in all types of substances! • Solids • Liquids • Gases

14. How does diffusion work? = impermeable BEFORE… AFTER… Equilibruim! Equilibruim!

15. Now you try! = impermeable

16. Facilitated Diffusion: • Facilitated Diffusion: is a specific type of diffusion using PROTEINS to transport large or charged molecules into the cell. • Remember that some molecules cannot get through the semi-permeable membrane on their own (large, polar, or charged). • This type of transport is still passive and does NOT require energy.

17. Facilitated Diffusion:

18. So which is which? Diffusion Facilitated Diffusion

19. Turn to page 204 in your textbook. Draw a diagram representing the cell membrane. Your drawing should include all of the following parts:- Phospholipid bilayer- membrane proteins-carbohydrate chain-a drawing of a labeled phospholipid-label the inside and outside of the cell(Yes, you need to use color!)