PowerPoint PresentationThe cell membrane is usually the outermost barrier of the cell.The cell wall is mainly for structural support and protection.The Plasma MembraneSlide 5The plasma membrane functions:Cell Identification---Plasma membrane is the membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell’s chemical environment.Slide 9Slide 10Biological membranes contain proteinsSinger and Nicholson: Fluid Mosaic Model---Fluidity in membranes means there is lateral two-dimensional movement of the lipids and some proteins in the plane of the membrane.Slide 14---Mosaic aspect of membranes means that there are proteins interspersed within the lipid bilayer.Some functions of membrane proteinsSlide 17Some of the recognition keys on the surface of cells are glycoproteinsSlide 19TRANSPORT ACROSS MEMBRANES Transport is movement. Movement of molecules requires two factorsSlide 21Passive transport: Movement down a concentration gradient - Doesn’t take a lot of energySlide 23Much of the movement of substances across membranes occurs by diffusion and therefore is a form of passive transport.Membranes are built to be selectively permeable.Two factors which influence permeability:Slide 27AquaporinsSlide 29Specialized proteins facilitate diffusion of selected solutesThree types of facilitated diffusionSlide 32Slide 33Slide 34Osmosis is the passive transport of water Osmosis is the diffusion of water across a differentially permeable membrane.Slide 36Slide 37The principles of osmosis:Note these are relative terms comparing one solution to another.Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will:ENERGY-REQUIRING TRANSPORT ACROSS MEMBRANESSlide 48Slide 49In active transport, the energy source that moves a molecule against its concentration gradient is:Slide 51Three types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis.---Phagocytosis (cell eating) is the endocytosis of solid particles. This may involve the formation of pseudopodiaSlide 54---Receptor-mediated endocytosis is the process of importing specific macromolecules into the cell by the inward budding of vesicles formed from coated pits, occurs in response to the binding of specific nutrients to receptors on the cell’s surface.---Receptor-Mediated EndocytosisCardiovascular DiseaseDepression MedicationsSlide 59Exocytosis moves material out of the cell.Connections between cells integrate cells into higher levels of structure and function (i.e., tissues and organs) Cells are connected by desmosomes.Slide 62If the connection between cells needs to be watertight, then tight junctions connect the cellsSlide 64Communication between cells occurs via gap junctions and plasmodesmataSlide 66Gap JunctionsPlants cells are often required to move large amounts of macromolecules or water. To accomplish this, wide interconnects known as plasmodesmata are used.Slide 69What type of cell junctions are needed for a tissue that must prevent fluids from leaking across its cell layer?Animal cells communicate with one another through:Chapter 5Cell Membrane Structure and FunctionThe cell membrane is usually the outermost barrier of the cell.An exception to this is found in cells which have a cell wallplants - cellulose fungi - chitinbacteria - chitin plus proteinsThe cell wall is mainly for structural support and protection. It usually doesn‘t act as a barrier to molecules trying to get in and out of the cells.The Plasma Membrane The plasma membrane contains the cell, but still allows the cell to interact with the environment (semi-permeable).Fig. 4.2The plasma membrane functions:1. Isolate the cell environment – keeps everything in the cell, inside the cell & keeps everything out of the cell, outside of the cell2. Regulate exchange between inside and outside3. Communicate with other cells4. Identify the cell typeCell Identification•Membrane proteins provide a ‘fingerprint’ for the cell type.•HIV binds to cell receptors that are present on cells inside the body, but not present on skin cells. Called CD receptors (cluster of differentiation).•This is why it is unlikely that you will contract HIV through casual contact.---Plasma membrane is the membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell’s chemical environment. 1. Membranes are made primarily of lipid2. Phospholipids are molecules which can form membranes naturallyFig. 5.3Cell membranes are phospholipid bilayersEvidence: The phospholipid content of red blood cells is just enough to cover the cell with two layers. The red blood cell has no internal membranes.Biological membranes contain proteinsEvidence: Membranes isolated from red blood cells contain proteins in addition to lipids.Singer and Nicholson: Fluid Mosaic ModelFig. 5.1---Fluidity in membranes means there is lateral two-dimensional movement of thelipids and some proteins in the plane of the membrane. However, transverse (flip-flop) across the membrane is rare.Majority of movement is from left to right.---Mosaic aspect of membranes means that there are proteins interspersed within the lipid bilayer.Some functions of membrane proteins 1. transport proteins channel proteins - porescarrier proteins - selective revolving doors2. receptors3. cell-to-cell recognitionglycoproteinextracellular fluid (outside)cholesterolphospholipid bilayerphospholipidrecognition proteinreceptor proteintransport proteincarbohydratebinding siteFig. 4.1Some of the recognition keys on the surface of cells are glycoproteins---Glycoproteins are proteins which have a carbohydrate attached to them.Glyco = sugarglycoproteinextracellular fluid (outside)cytoplasm (inside) cholesterolphospholipid bilayerphospholipidrecognition proteinreceptor proteintransport proteinprotein filamentscarbohydratebinding siteFig. 4-1TRANSPORT ACROSS MEMBRANESTransport is movement.Movement of molecules requires two factors1. Movement must be through a fluid - liquid or gas2. There must be a concentration gradient-difference in the amount of molecules from one place to anotherMolecules in a fluid always move. If there is a concentration gradient then the movement has a specific direction.Fig. 5.6Passive transport: Movement down a concentration gradient - Doesn’t take a lot of energy---Concentration gradient is a concentration change over a
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