1. What did you observe about membrane behavior from this video?
The Cell Membrane
What did you observe about membrane behavior from this video?

2. Movement Across Membranes
Cell membrane is selectively permeable:
Small, non-lipid soluble molecules (water)
Look at the membrane model again. How do you think the following materials get in/out?:
Small, lipid soluble molecules (hydrocarbons)
Macromolecules (starches)
Large, nonpolar molecules (glucose)

4. Effect of Phospholipid Structure

5. Fluidity
Watch the membranes – are they rigid? If not, how do they move?
Rate molecules move within & across membranes depends on
temperature
structure of hydrocarbon tails in bilayer

6. Membrane Transport

7. Solute Movement across Lipid Bilayers
Materials move across membrane in different ways.
1. Passive transport does not require energy input
2. Active transport energy required for substances to cross the membrane.
Small molecules and ions in solution are called solutes, have thermal energy, and are in constant, random motion.
Differences in solute concentration across the membrane create a concentration gradient
Molecules and ions move randomly when a concentration gradient exists, but there is a net movement from high- concentration regions to low-concentration regions. Diffusion along a concentration gradient increases entropy and is thus spontaneous.

8. Goal? Reaching Equilibrium!
One way to do this is diffusion – direct movement of solutes from areas of high to low concentration NO energy required = PASSIVE transport

9. Osmosis
Does water move towards high solute concentration? Low solute concentration?
Does water concentration move from high to low or low to high concentration?

10. Hyper-, Hypo-, & Isotonic

11. Let’s practice

12. Hyper-, Hypo-, or Isotonic? (in your notes)
Use arrows to show the direction of water movement into or out of each cell.

13. Label the Plant Cell
What type of solution are they in?

14. Label the Red Blood Cells Why should you worry about this?
What type of solution are they in?

15. Membrane Proteins Affect Ions and Molecules
Transmembrane proteins that transport molecules are transport proteins.
THREE broad classes of transport proteins; each affects membrane permeability:
Channels
Carrier proteins or transporters
Pumps

16. Movement affects gradient, affects continued movement

17. Facilitated Diffusion vs. Pumps
Facilitated diffusion – PASSIVE transport of substances using specific channel proteins Ex: GLUT-1 transport protein increases permeability of membrane to glucose
Protein Pumps – ACTIVE transport using ATP to move substances against concentration gradient Ex: Sodium/Potassium Pump transports Na+ & K+ against electrochemical gradient

18. Active Transport: Pumps
This can set up a gradient that “switches” on the transport of other materials. This is called secondary transport or cotransport.

19. Active Transport: Endo/Exocytosis

20. Summary of Membrane Transport
Give examples of types of transport across the membrane.
Diffusion and facilitated diffusion are forms of ________transport and thus move materials down their concentration gradient and ________require an input of energy.
______transport moves materials against their concentration gradient and _______energy provided by _____or an electrochemical gradient.

21. Homework Scenario
Intraveneous solutions must be prepared so they are isotonic to red blood cells. A 0.9% salt solution is isotonic to red blood cells.
a. Explain what would happen if you placed a red blood cell in a solution of 99.3% water and 0.7% salt.
b. Explain what would happen if you placed a red blood cell into a solution of 90% water and 10% salt.

22. 2. What would happen to a cell if placed in the following solutions
2. What would happen to a cell if placed in the following solutions? Explain in detail and illustrate.
Hypotonic
Isotonic
Hypertonic