BIOL 101 1st Edition Lecture 7 Outline of Last Lecture I Nucleic Acids a Types b Flow c Monomers d Linkage e Structure of DNA II Lipids a Functions b Groups c Fats d Saturated e Unsaturated f Trans Fat g Phospholipids h Steroids Outline of Current Lecture I Cytoplasmic Membrane II Fluid Mosaic Model These 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 Functions IV Fluid Nature V Traffic of Molecules VI Water Balance in Cells VII Transport Current Lecture Chapter 7 Membrane Structure and Function I II III Cytoplasmic Membrane a Also called a plasma membrane b A boundary that separates the living cell from its non living surroundings c A barrier but also controls traffic in and out of the cell d Selectively permeable lets some things pass but not others e Unique membrane structure makes life possible Fluid Mosaic Model of Membrane Structure a Membrane is a mosaic of different macromolecules b Base layer is made of phospholipids c Heads of phospholipids are hydrophobic water loving i Face towards inside and outside of cell ii Heads are polar d Tails of phospholipids are hydrophobic water fearing e Many molecules associate with the phospholipid bilayer Functions of the Membranes a Determined by the proteins that associate with it b 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 bilayer 1 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 bilayer c Carbohydrates associated with the membrane serve in cell cell recognition i Face the outside of the cell ii 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 membrane ii Affects the fluidity of the membrane IV V VI e The membrane is bifacial meaning it looks different from the inside than it does from the outside Fluid Nature of the Membrane a Not a rigid structure b Phospholipids are constantly moving dynamic c Consistency like salad oil d Fluid nature is important for proper function Traffic of Molecules a Hydrophobic middle is the main barrier to small molecules b Small hydrophobic nonpolar molecules move easily across it because hydrophobia does not affect them c Hydrophilic molecules polar have a much harder time i Ex H2O and CO2 get across by moving between the phospholipid molecules ii Ex Sugar and charged atoms or molecules get across by using transport proteins integral transmembrane proteins that move molecules across d Two basic kinds of transport proteins i Channels provide hydrophilic tunnel through the membrane designed for a specific molecule or related molecules ii Carrier proteins hold onto specific molecules and then change shape to shuttle them across the membrane e Diffusion most traffic occurs through this method i Net movement of a substance down its concentration gradient ii Diffuses from where it is more concentrated to where it is less concentrated iii Each substance diffuses frown its own concentration gradient iv Spontaneous process v Energy for the movement comes from the concentration gradient f Passive transport diffusion across a biological membrane g Osmosis diffusion of H2O across a membrane Water Balance in Cells a Diffuses down its concentration gradient i More concentration less concentration b Affected most by the amount of solutes dissolved in the H2O i More solutes less H2O diffuses c 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 that d Three possibilities i Hypertonic hyperosmotic environment outside of the cell 1 Concentration of solutes in the water is greater outside of the cells 2 Concentration of H2O that is FREE TO MOVE is then greater inside the cells 3 H2O diffuses out of cell SHRINKING it ii Hypotonic hyposmotic environment outside of the cell 1 Concentration of solutes is greater inside the cell 2 Concentration of water that is FREE TO MOVE is inside 3 H2O diffuses into the cell causing it to SWELL a In animal cells causes cell to explode cell lipis VII 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 inside 2 No NET movement in or out a Animal cell ideal condition b Plant cell no turgor pressure plant wilts Transport a Facilitated Diffusion i Example of passive transport because it utilizes transport proteins for diffusion ii Solute moves down its concentration gradient iii No energy is required from the cell iv Cell has to provide a transport protein b Active Transport i Solute is moved AGAINST the concentration gradient ii Requires a transport protein for that particular solute iii Requires energy input from the cell c Ion Transport i 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 membrane iii Membrane potential affects all CHARGED substances across the membrane d Two forces drive the transport of ions i Concentration gradient of the specific ion 1 Ions diffuse down their electrochemical gradient ii Membrane potential most cells have a net negative charge 1 ions are favored to enter the cell 2 ions are favored to exit the cell