BIOL 101 1st Edition Lecture 7Outline of Last Lecture I. Nucleic Acidsa. Typesb. Flowc. Monomersd. Linkagee. Structure of DNAII. Lipidsa. Functionsb. Groupsc. Fatsd. Saturatede. Unsaturatedf. Trans Fatg. Phospholipidsh. SteroidsOutline of Current Lecture I. Cytoplasmic MembraneII. Fluid Mosaic ModelThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. FunctionsIV. Fluid NatureV. Traffic of MoleculesVI. Water Balance in CellsVII. TransportCurrent LectureChapter 7 – Membrane Structure and FunctionI. Cytoplasmic Membranea. Also called a plasma membraneb. A boundary that separates the living cell from its non-living surroundingsc. A barrier, but also controls traffic in and out of the celld. Selectively permeable – lets some things pass, but not otherse. Unique membrane structure makes life possibleII. Fluid Mosaic Model of Membrane Structurea. Membrane is a mosaic of different macromoleculesb. Base layer is made of phospholipidsc. Heads of phospholipids are hydrophobic (water loving)i. Face towards inside and outside of cellii. Heads are polard. Tails of phospholipids are hydrophobic (water fearing)e. Many molecules associate with the phospholipid bilayerIII. Functions of the Membranesa. Determined by the proteins that associate with itb. 2 major kinds of membrane proteins:i. Integral membrane proteins – embedded in the phospholipid bilayer with hydrophobic parts of the protein interacting with the hydrophobic middle of the bilayer1. Some stick to the outside of the cell, some are inside (unilateral)2. Some stick out on both sides (transmembrane)ii. Peripheral membrane proteins – not actually attached the the cell, rather stuck on another molecule that is attached to the phospholipid bilayerc. Carbohydrates associated with the membrane serve in cell-cell recognitioni. Face the outside of the cellii. Act as molecule “ID tags”iii. Covalently bond to proteins (glycoproteins)iv. Covalently bond to lipids (glycolipids)d. Cholesterol i. Lipid embedded in the hydrophobic middle of the membraneii. Affects the fluidity of the membranee. The membrane is “bifacial” meaning it looks different from the inside than it does from the outsideIV. Fluid Nature of the Membranea. Not a rigid structureb. Phospholipids are constantly moving (dynamic)c. Consistency like “salad oil”d. Fluid nature is important for proper functionV. Traffic of Moleculesa. Hydrophobic middle is the main barrier to small moleculesb. Small hydrophobic (nonpolar) molecules move easily across it because hydrophobia does not affect themc. Hydrophilic molecules (polar) have a much harder timei. Ex: H2O and CO2 get across by moving between the phospholipid moleculesii. Ex: Sugar and charged atoms or molecules get across by using transport proteins integraltransmembrane proteins that move molecules acrossd. Two basic kinds of transport proteinsi. Channels – provide hydrophilic tunnel through the membrane designed for a specific molecule or related moleculesii. Carrier proteins – hold onto specific molecules and then change shape to shuttle them across the membranee. Diffusion – most traffic occurs through this methodi. Net movement of a substance down its concentration gradientii. Diffuses from where it is more concentrated to where it is less concentratediii. Each substance diffuses frown its own concentration gradientiv. Spontaneous processv. Energy for the movement comes from the concentration gradientf. Passive transport – diffusion across a biological membraneg. Osmosis – diffusion of H2O across a membraneVI. Water Balance in Cells a. Diffuses down its concentration gradienti. More concentration  less concentrationb. Affected most by the amount of solutes dissolved in the H2Oi. More solutes = less H2O diffusesc. To determine where the concentration of FREE TO MOVE water is, figure out where the concentration of solutes is higher, and the water is opposite of thatd. Three possibilities:i. Hypertonic (hyperosmotic) environment outside of the cell1. Concentration of solutes in the water is greater outside of the cells2. Concentration of H2O that is FREE TO MOVE is then greater inside the cells3. H2O diffuses out of cell, SHRINKING itii. Hypotonic (hyposmotic) environment outside of the cell1. Concentration of solutes is greater inside the cell2. Concentration of water that is FREE TO MOVE is inside3. H2O diffuses into the cell, causing it to SWELLa. In animal cells, causes cell to explode (cell lipis)b. In plant cells, it swells up but doesn’t explode because the cell wall protects it, building up the turgor pressure (optimal condition)iii. Isotonic (isosmotic) 1. Concentration of solutes outside = concentration of solutes inside2. No NET movement in or outa. Animal cell – ideal condition b. Plant cell – no turgor pressure, plant wiltsVII. Transporta. Facilitated Diffusioni. Example of passive transport because it utilizes transport proteins for diffusionii. Solute moves down its concentration gradientiii. No energy is required from the celliv. Cell has to provide a transport proteinb. Active Transporti. Solute is moved AGAINST the concentration gradientii. Requires a transport protein for that particular soluteiii. Requires energy input from the cellc. Ion Transporti. Moving charged atoms or molecules requires the analysis of the membrane potential (voltage across the membrane)ii. All cells have voltage – potential electric energy due to separation of charge across the membraneiii. Membrane potential affects all CHARGED substances across the membraned. Two forces drive the transport of ions:i. Concentration gradient of the specific ion1. Ions diffuse down their electrochemical gradientii. Membrane potential – most cells have a net negative charge1. + ions are favored to enter the cell2. – ions are favored to exit the