1. 1 Transport through cell membranes

2. Cell Membrane

3.  Physical and chemical outer boundary in animal cells  Made of two lipid (fat) layers and proteins  Proteins give the cell its unique “personality” or function

4. Function of Membrane Proteins 1. Transport (in and out of cell) 2. Receptors 3. Cell adhesion 4. Cell recognition

5. 5 Transport through cell membranes Cell membrane regulates what enters and leaves the cell. For the cell to survive, some materials need to be able to enter and leave the cell. 4 basic mechanisms: 1. DIFFUSION 1. FACILITATED DIFFUSION 2. OSMOSIS 3. ACTIVE TRANSPORT

6. Diffusion  The net movement of molecules from a region of high concentration to a region of lower concentration.  Requires no energy!  As a result of diffusion, molecules reach an equilibrium where they are evenly spread out. 6

7. 7 Diffusion through a membrane Inside cell Outside cell

8. 8 Diffusion through a membrane Cell membrane Inside cell Outside cell diffusion

9. 9 Diffusion through a membrane Cell membrane Inside cell Outside cell EQUILIBRIUM

10. 10 Molecules that diffuse through cell membranes Oxygen Carbon dioxide Water.

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12. 12 Facilitated Diffusion through a membrane Cell membrane Inside cell Outside cell Protein channel

13. 13 Facilitated Diffusion through a membrane Cell membrane Inside cell Outside cell Protein channel diffusion

14. 14 Facilitated Diffusion through a membrane Cell membrane Inside cell Outside cell Protein channel diffusion EQUILIBRIUM

15. 15 Osmosis The diffusion of water from high concentration to low concentration of water across a selectively permeable membrane The diffusion of water from high concentration to low concentration of water across a selectively permeable membrane

16. 16 Osmosis Cell membrane partially permeable. Inside cell Outside cell VERY High conc. of water molecules. High water potential. VERY Low conc. of water molecules. High water potential. Sugar molecule DILUTE SOLUTION CONCENTRATED SOLUTION

17. AS Biology, Cell membranes and Transport17 Osmosis Cell membrane partially permeable. Inside cell Outside cell High conc. of water molecules. High water potential. Low conc. of water molecules. High water potential. OSMOSIS

18. AS Biology, Cell membranes and Transport18 Osmosis Cell membrane partially permeable. Inside cell Outside cell OSMOSIS EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water

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21. 21 Active Transport

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23. Active Transport cell uses energy actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration (Low  High) Three Types:

24. Types of Active Transport 1. Protein Pumps - transport proteins that require energy to do work Example: Sodium / Potassium Pumps are important in nerve responses. Animation Sodium Potassium Pumps Sodium Potassium Pumps (Active Transport using proteins) Protein changes shape to move molecules: this requires energy!

25. Types of Active Transport  2. Phagoocytosis: taking bulky material into a cell Uses energy Uses energy Cell membrane in-folds around particle Cell membrane in-folds around particle “cell eating” “cell eating” Forms vacuole around particle & digests food Forms vacuole around particle & digests food This is how white blood cells eat bacteria! This is how white blood cells eat bacteria!

26. Types of Active Transport 3. Pinocytosis: Cell membrane folds inward Cell membrane “pinches” in Cell membrane “pinches” in Cell changes shape – requires energy Cell changes shape – requires energy EX: Hormones or wastes released from cell by pinocytosis EX: Hormones or wastes released from cell by pinocytosis active transport animation active transport animation active transport animation active transport animation Endocytosis & Exocytosis Endocytosis & Exocytosis animations

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28. 28 EndocytosisEndocytosis - a molecule causes the cell membrane to bulge inward, forming a vesicle. Phagocytosis - an entire cell is engulfed. Pinocytosis - external fluid is engulfed. Receptor-mediated Phagocytosis Endocytosis Phagocytosis