Chapter 7 and 11 Membrane StrunctionStrunction Fluid Mosaic Model Fluidity: P.Membrane (PM) held together by weak hydrophobic interactions Lateral drifting ability Lipids Proteins: some stable/attached to cytoskeleton Temperature Dependent Mosaic Protein collage: >50 proteins Classes: Integral Proteins:Integral Proteins Transmembrane proteins Penetrate hydrophobic core of membrane Peripheral Loosely bound to surface Attached to cyto-skeleton or ECM (Extracellular matrix) Review: Review: What organelles are responsible for creating membrane proteins? Selective Permeability General rule: like dissolves like Non-polar/hydrophobic solutes dissolve in lipid Ions and hydrophillic solutes dissolve in water Selective Permeability: some substances can pass more easily than others CO 2, hydrocarbons, lipids, and O 2 are nonpolar (can pass lipid membrane core easily) Water, glucose, sugars, charged ions (cannot pass lipid core easily) so must use hydrophillic transport proteins to pass (ex. Aquaporins) Aquaporins Small molecules are more permeable than larger ones Passive Transport Mvmt down [gradient] Spontaneous process G Types of Passive Transport: Diffusion Osmosis Facilitated Diffusion Diffusion Diffusion molecules of any substance moves down [gradient] Osmosis Osmosis (tonicity dependent) Isotonic vs. hypotonic vs. hypertonic conditions Water always moves from hypotonic to hypertonic side Balancing Water Uptake Animals: cannot tolerate change in tonicity Ex. Salt water fish vs. fresh water fish, vice versa Some Freshwater protists prevent lysing due to contractile vacuoles Balancing Water Uptake Plants: Cell walls help maintain water balance Turgid Conditions Good!Turgid Flacid Conditions cause plasmolysisplasmolysis (lab 1E review) Function of Membrane Proteins protein channels for passive transportpassive transport protein pumps for active transport Catalysis of Chemical Reactions at the Membrane Surface substrates bind to protein surface sends a signal within the cell to start a chemical chain reaction or cell responsesends a signal oligosaccharides on proteins or lipids act as name tags for cells. Ex. Gap Junctions, Tight Junctions, etc. Maintenance of Cell Shape End of Slide Show Facilitated Diffusion diffusion of solutes (ions) with help from channel proteins in the plasma membrane Active Transport Movement against [gradient] Nonspontaneous, + G, Requires ATP Types: Protein pumps Cotransport Exocytosis: Phagocytosis and Pinocytosis Endocytosis Receptor Mediated Endocytosis Active Transport generates an electrochemical gradient: charge difference (disequilibrium) between both sides of the membrane Protein Pumps Ex 1: Sodium-Potassium PumpSodium-Potassium (take notes about the function of Na/K pump from the video) Sodium-Potassium Pump 3-D overview3-D overview Ex 2: Pumping H + ions into lysosome to create acidic envt Co-transport Involves the transport of a substance against a concentration gradient powered indirectly by an ATP powered pump H+ ATP H+ ADP + Pi Exocytosis Fusing of vesicles to the plama membrane, thus releasing its contents Endocytosis Back to Function of Membrane Proteins The engulfing of substances by pseudopods extensions of the plasma membrane Three types: Phagocytosis (cell eating lg. particles engulfed)Phagocytosis Pinocytosis (cell drinking sm. ions and liquids engulfed) Receptor Mediated Endocytosis (use of surface proteins to engulf a specific substrate)Receptor Signal Transduction 3 Stages of Signal Transduction 1)Reception: A ligand (analogous to a substrate) binds to receptor protein. Receptor proteins can be on the cell surface, but not always. Receptor protein changes shape 2)Transduction: Amplifies and sends the signal through chemical relay 3)Cell Response: Specific response is triggered Examples of Signal Transduction Why is this hormone-receptor protein not found on the surface of the plasma membrane? Steroids and Hormones are types of lipids, which can pass through phospholipid membranes easily. Back to Function of Membrane Proteins