Chapter 5 Membrane Structure and Function
Read chapter 5 in textbook Read Lab 1 (Osmosis and Diffusion) Read appropriate lab and lecture pages in pages in CliffsAP Cell Surface SEM Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
Topics 5.1 Plasma Membrane Structure and Function 5.2 5.3Permeability of the Plasma Membrane 5.4Modification of Cell Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function5.1 Plasma Membrane Structure and Function All cells have a plasma membrane Functions differently in different cells All have same basic makeup Currently the fluid mosaic model is thought to be the best representation Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Actively functioning part of cell without it cells die Selectively permeable Composed of double layer of phospholipid with free floating proteins imbedded in it (proteins can float laterally) Also contains glycolipids, cholesterol and glycoproteins Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Hydrophilic phosphate heads Hydrophobic fatty acid tails water soluble substances cannot pass easily ( amino acids, sugars, proteins, nucleic acids) substances soluble in lipids can pass more easily (O2, CO 2) Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Fluid Mosaic Membrane is fluid because phospholipids are oil consistency at body temperature Proteins can float around between phospholipds Membrane is mosaic because it has a wide range of movable proteins imbedded in it Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Mosaic Quality Proteins give unique qualities to cells RBC has over 50 different proteins associated with it Proteins are of two major types Peripheral proteins Integral proteins Proteins can account for 50% of wt of membrane Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Peripheral Proteins Occur on inside or outside of membrane Dont span the membrane Often attached to integral protein Function: Can have structural role Sometimes enzymatic Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral proteins Most span the entire membrane Have hydrophilic and hydrophobic portions Function as : Receptors Channels or pores Carriers Enzymes Cell recognition Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral Proteins Channel protein Mills AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral Proteins Carrier/Transport protein Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral Proteins (usually) Cell recognition proteins, fingerprints of the cell These glycoproteins and/or glycolipids are specific for each species, for individuals within a species and even for different types of cells within the same individual Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral Proteins Receptor protein Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Integral Proteins Enzymatic protein Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Junction Protein Junction Proteins: Tight junctions join cells so that a tissue can fulfill a function, as when a tissue pinches off the neural tube during development. Without this cooperation between cells, an animal embryo would have no nervous system. Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Plasma Membrane Structure and Function Glycoproteins Most proteins that abut the extracellular space are associated with branching sugar groups (glycocalyx) Branching carbohydrates Cell surface sticky Distinct for each cell type - also mark cells as self Mills AP Biology 2012 Cystic Fibrosis Problem with a membrane protein
Or (on hard drive) cystic fibrosis membrane protein Mills AP Biology 2012 Chapter 5 Membrane Structure and Function Permeability of the Plasma Membrane
How do substances get into and out of cells? Pg CliffsAP What determines whether or not a substance will enter or exit a cell? Outside of cell - interstitial fluid (intercellular fluid, extracellular fluid) Inside of cell - intracellular fluid Must maintain balance each has its own make up Membrane selectively permeable if cell looses this property, cell will die Mills AP Biology 2012 Chapter 5 Membrane Structure and Function Permeability of the Plasma Membrane
Selectively (differentially) permeable membrane Properties due in part to: Hydrophilic phosphate heads Hydrophobic fatty acid tails Small, non charged, lipid soluble substances (O2, alcohol) pass easily Some small polar molecules (water, carbon dioxide) pass fairly easily Large and or charged substances and macromolecules need help to pass water soluble substances cannot pass easily ( amino acids, sugars, proteins, nucleic acids) Mills AP Biology 2012 Chapter 5 Membrane Structure and Function Permeability of the Plasma Membrane
Active processes Active transport Bulk transport endocytosis pinocytosis phagocytosis receptor mediated endocytosis transcytosis exocytosis E needed from cell (ATP) Passive processes Diffusion Facilitated diffusion Osmosis(water diffusion) Filtration no E needed from cell Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Passive Process - Diffusion down concentration gradient distributes until equilibrium reached influenced by: distance, temperature, weigh, concentration small particles, lipid soluble particles can diffuse across membrane. O2, CO2, steroids, general anesthetics (lipid soluble), water (small), alcohol-can diffuse. Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Passive Process - Osmosis (diffusion of water) water molecules move from area of greater water concentration to area of lesser water concentration across a selectively permeable membrane Mills AP Biology 2012 Mills AP Biology 2012 Isotonic, hypotonic, hypertonic
Osmotic pressure Isotonic, hypotonic, hypertonic Mills AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Tonicity Hypertonic Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Tonicity Hypotonic Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Tonicity Isotonic Osmosis demo site: Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Passive Process - Facilitated Diffusion uses a carrier molecule protein channels and protein carriers Proteins are specific to the substance they transport amino acids and sugars too large for pores and arent lipid soluble Na, K, Cl ions too large, also charged rate depends on binding rate and concentration down concentration gradient glucose carrier activated by insulin Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Water molecule Sodium molecule Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Facilitated Diffusion ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Facilitated Diffusion.dir Mills AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Passive Transport Across a Membrane Passive Process - Filtration molecules forced through membrane by blood pressure this is how tissue fluid formed blood pressure too high --->tissue edema urine formed in kidneys down a pressure gradient Mills AP Biology 2012 Chapter 5 Membrane Structure and Function
Active processes active transport bulk transport endocytosis pinocytosis phagocytosis receptor mediated endocytosis exocytosis E needed from cell (ATP) Passive processes diffusion facilitated diffusion osmosis (water diffusion) filtration no E needed from cell Mills AP Biology 2012 Active Process - Active Transport
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process - Active Transport moves particles up concentration gradient from low concentration to high involves carrier proteins-pumps often coupled reactions ( Na - K pump) very important for homeostasis useful for amino acids, sugars and ions Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane NORMAL CONDITIONS More K inside cell than outside More Na outside cell than inside Na - K Pump Pumps ions up concentration gradients. 2 K into cell for every 3 Na out of cell. Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Transport Animation ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\active transport animation.mov Mills AP Biology 2012 Active Process - Bulk Transport
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process - Bulk Transport Exocytosis moves particles out of cell requires energy nerve cells use to secrete neurotransmitter Transcytosis ferries particles across cell Endocytosis moves particles into cell requires energy particles too large for diffusion or active transport three types: pincytosis phagocytosis receptor mediated endocytosis Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process - Endocytosis - Pinocytosis liquid droplets, cell drinking small (0.1um) vesicles most cells use, esp. cells that function in absorption Mills AP Biology 2012 Different stages of the pinocytosis, an endocytic process, in an endothelial cell. The vessel lumen is to the right; the underlying connective tissue is to the left. Notice the thin gray (electron-dense) line of the basal lamina immediately along the left border of the cell. 1 = Vesicle open to the outside of cell, facing the extracellular matrix; 2 = Vesicle partially enclosed by cell membrane; 3 = Vesicle limited by membrane and wholly within cytoplasm of cell. The elongate nucleus lies in the center of the cell. Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process - Endocytosis - Phagocytosis cell eating vesicles larger WBCs, macrophages combine with lysosome, get digested Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Phagocytosis animation..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\phagocytosis animation and tutorial.swf Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane ActiveProcess - Endocytosis - Receptor mediated endocytosis moves specific particles (ligands) receptor proteins on cell membrane insulin, cholesterol taken into cells this way Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process - Exocytosis Moves particles out of cell vesicles form within cell proteins can be secreted this way Mills AP Biology 2012 Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Active Transport Across a Membrane Active Process -Transcytosis Ferries particles from one side of cell to other important in HIV transmission Mills AP Biology 2012 Passage of Molecules into and out of Cells
Uses energy Name Direction Requirement Examples Passive Processes No Diffusion Osmosis Toward lower concentration Concentration gradient Lipid soluble molecules, water, gasses Facilitated diffusion Concentration gradient and carrier Some sugars and amino acids Active Processes Yes Active Transport Toward greater concentration Carrier Other sugars, amino acids and ions Exocytosis Toward outside Vesicle Macromolecules Endocytosis Toward inside Vacuole Cells and subcellular material Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Many cells have modifications that are exterior to the plasma membrane Plants, bacteria, algae and fungi have cell walls Animals have extracellular matrix Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Extracellular Matrix of Animal Cells Meshwork of insoluable glycoproteins and proteoglycans Fills spaces between cells, supports cells Influences cell development, migration, shape and function Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Desmosomes (Adhesion junctions) spot welds, scattered like rivets binds cells together and reduces tension Found in skin, heart muscle, neck of uterus,stomach, bladder Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Tight junctions protein molecules in adjacent cells fuse together Impermeable,zipperlike junction digestive tract epithelium, nephrons capillaries of brain Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Gap junctions allow chemical substances to pass from one cell to another, adjacent channel proteins join Found in electrically excitable tissue - heart muscle, smooth muscle important in embryonic cells prior to circulatory system Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Mills AP Biology 2012 Chapter 5 Membrane Structure and Function 5
Chapter 5 Membrane Structure and Function Modifications of Cell Surfaces Plant Cell Walls Freely permeable, variable in thickness All plants have a primary cell wall composed cellulose, pectin and noncellulose polysaccharides Some plants (esp woody) have a secondary cell wall composed of lignin and cellulose Plasmodesmata (only in plants) Narrow, membrane lined channels that connect cells cytoplasm Mills AP Biology 2012 Read Connecting the Concepts on pg 101
THE END Mills AP Biology 2012