Cell Membranes and Osmoregulation

Ch 7 and Ch 44

OutlineI. Types of membrane proteins

1. IntegralA. Transport

a. Channels – Facilitated diffusion EX: Aquaporinb. Gated Channelsc. Pumps – Na-K

B. EnzymeC. Signal Transduction

2. PeripheralA. Gap Junction

a. Plant = plasmodematab. Animal – 3 types ( Tight, Desmosomes, Gap)

B. Cell-to-cell recognitionC. Attachment to EMC and cytoskeleton

II. Membrane Structure results in selective permeability, transport, osmoregulation

III. The Kidney

The Fluid Mosaic Model

• Structural components of the membrane are weakly bonded and flow laterally

• How is the above experiment evidence of this concept?

The Mosaic: Diverse Structures and Functions of Membrane Proteins

Aquaporin, Na-K Pump

Part of the ER, help modify and assemble

Insulin Receptor

Antigens and antibodies

Cell junctions

Integral vs PeripheralTransmembrane; Amphipathic, Alpha-helix coils Extracellular matrix and cytoskeleton

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?

Cellular Junctions• Plants– Plasmodesmata• Allow ions to pass

from cell to cell.

• Animals– Junctions are

specialized for certain functions

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

Membrane structure results in selective permeability

Movement of water is especially important to cells

• Where might the hydrophobic parts be?

• Hydrophilic?

• How might influx of water be controlled?

Osmosis and Tonicity control the movement of water

Osmoregulation• Balance between uptake and loss of water and solutes

Feedback control of osmoregulation…remember this?

Mammalian Excretory System