Cell Membranes and Osmoregulation

1. Cell Membranes and Osmoregulation Ch 7 and Ch 44

2. Outline • Types of membrane proteins • Integral • Transport • Channels – Facilitated diffusion EX: Aquaporin • Gated Channels • Pumps – Na-K • Enzyme • Signal Transduction • Peripheral • Gap Junction • Plant = plasmodemata • Animal – 3 types ( Tight, Desmosomes, Gap) • Cell-to-cell recognition • Attachment to EMC and cytoskeleton • Membrane Structure results in selective permeability, transport, osmoregulation • The Kidney

4. The Fluid Mosaic Model • Structural components of the membrane are weakly bonded and flow laterally • How is the above experiment evidence of this concept?

5. The Mosaic: Diverse Structures and Functions of Membrane Proteins Aquaporin, Na-K Pump Cell junctions Part of the ER, help modify and assemble Antigens and antibodies Insulin Receptor

6. Integral vs Peripheral Transmembrane; Amphipathic, Alpha-helix coils Extracellular matrix and cytoskeleton

7. How do membranes get their proteins? Sidedness? • See Figure 7.12 and sketch the Draw It! assignment in your notebook • Role of the endomembrane system? • Endogenous or Exogenous?

8. Cellular Junctions • Plants • Plasmodesmata • Allow ions to pass from cell to cell. • Animals • Junctions are specialized for certain functions

9. Animal Junctions • Tight Junction: Prevents movement of fluid between cells. • Desmosome: Adheres two cells, very common in epidermis • Gap Junction: Allows ions to pass directly from cell to cell

10. Membrane structure results in selective permeability

11. Movement of water is especially important to cells • Where might the hydrophobic parts be? • Hydrophilic? • How might influx of water be controlled?

12. Osmosis and Tonicity control the movement of water

13. Osmoregulation • Balance between uptake and loss of water and solutes

14. Feedback control of osmoregulation…remember this?

15. Mammalian Excretory System