THE CELL MEMBRANE CHAPTER 5

Fluid Mosaic Model

Fundamental Architecture of Cell Membranes Phospholipid Bilayer Transmembrane Proteins Interior protein Network Cell Surface Markers ( glycoproteins and glycolipids)

How can we see the membrane? Electron Microscopy Freeze fracturing

Membrane Fluidity Saturated vs Unsaturated fats Bacteria Temperature

Proteins in the Membrane Transporters Enzymes Cell surface receptors Cell surface identity markers Cell-to-cell adhesion proteins Attachments to the cytoskeleton

Transmembrane Domains Alpha Helices, span membrane at least once

Pores Betapleated sheets

Passive Transport Across Membranes Moving Down a concentration gradient Diffusion

Proteins in Diffusion Channel Proteins Carrier Proteins –Make membrane selectively permeable

Ion Channels Can be gates 3 conditions determine net movement –Concentrations across membrane –Voltage difference –The state of the gate

Facilitated Diffusion Still Passive Diffusion rate depends on the amount of available receptors Can reach saturation Specific to certain molecules or ions Found in RBCs (glucose and Chloride HCO 3 )

Osmosis Movement of water across membranes Solvents vs Solutes Osmotic Concentration:Hyp ertonic vs Hypotonic vs Isotonic Aquaporins Hydrostatic Pressure

Methods of Maintaining Balance Extrusion- found in many single-celled eukaryotes….contractile vacoules Isomotic Regulation- organisms that live in the ocean Turgor- plant cells

Active Transport Uses Energy Moves against concentration gradient Uniporters vs symporters vs antiporters

Sodium Potassium Pump

Coupled Transport Uses ATP indirectly Uses the energy created by another transport to move a molecule up their concentration gradient ex. glucose

Endocytosis Cell takes in materials Phagocytosis Pinocytosis Can be Receptor mediated

Exocytosis Material leaves the cell