BIOL 1441 1st Edition Lecture 12 Outline of Last Lecture I. Plasma membranea. Fluidityb. CholesterolII. Membrane proteinsa. 6 major functionsIII. Permeability of the lipid bilayera. Polar vs nonpolarb. Transport proteinsIV. Types of transporta. Diffusionb. Osmosis Outline of Current Lecture I. Osmoregulation a. With cell wallsII. Facilitated diffusionIII. Active transportIV. Membrane potentialV. Electrochemical gradientThese 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.VI. Electrogenic pumpCurrent LectureI. Osomoregulation- water balancea. To maintain their internal environment- osmoregulateb. Control the balance of water within themselves and the outside environmentc. Paramecium lives in a hypotonic environment (pond water)i. Contractile vacuole that acts as a pumpii. SINCE IT LIVES IN HYPOTONIC ENVIRONMENT, PARAMECIUM= HYPERTONICd. Water Balance with Cell Wallsi. Hypotonic environment- plant cell swells, cell wall exerts pressure, opposes uptake- turgid (firm)1. Water flows INTO plant cell-stands straight upii. Isotonic environment- no net movement of water; flaccid (wilt)iii. Hypertonic environment- plant cells lose water 1. Water flows out of cell- Shrivels up2. Plasmolysis- plasma membrane pulls away from the walle. Tonicity and Osmoregulationi. Tonicity- ability of a solution to cause a cell to gain or lose water1. how a solution gains/loses waterii. Osmoregulation- animals/plants control the balance of water within themselves and the outside environment1. how we manage water balanceiii. ANIMAL CELLS LIKE ISOTONIC SOLUTIONSiv. PLANT CELLS LIKE HYPOTONIC SOLUTIONII. Facilitated Diffusion: Passive diffusion aided by transport proteinsa. Transport proteins speed movement of polar molecules across the plasma membranei. Very specific, water or small ionsb. Channel proteins- provide corridors that allow a specific molecule or ion to cross the membranec. Ion channels- gated channels, stimulus causes them to open/closei. Stimulus- chemical or electricalii. Chemical- not the substance that will be transported1. Neurotransmitter can open Na+ ion channelsd. Carrier proteins – undergo change in shape that translocates the solute-binding site across the membraneIII. Active Transport: Moves solutes against their gradientsa. Moving solutes from LOW concentration to a HIGH concentrationi. AGAINST THE GRADIENTb. Active transport- requires energy, usually ATPc. Performed by carrier proteins onlyi. Channels are just open passage waysd. Sodium-potassium pump- higher concentration of K+ and lower concentration of Na+ inside the cell compared to environmenti. Both cationsii. Is a transport proteiniii. Maintains concentration gradients of sodium and potassium across cell membranes1. Pumps 3 Na+ OUT of cell2. Pumps 2 K+ INTO cell3. Inside of cells are NEGATIVE4. Inside of cell has LOW sodium (Na+)5. Inside of cell has HIGH potassium (K+)6. If Na+ channels are opened, Na+ diffuses INTO cell7. If K+ channels are opened, K+ diffuses OUT of the cellIV. Membrane Potentiala. All cells have voltage across their plasma membranesb. Voltage: electrical potential energy, separation of opposite chargesc. Cytoplasm has a negative charge compared to extracellular fluidi. Unequal distribution of anions (- ions) & cations (+ ions)d. Membrane potential - voltage difference across a membranei. Separate charges across a membranee. Range -50 to -200 mVi. Minus sign indicated negative inside the cell compared to outsidef. Acts like a battery- energy source that affects the trafficking of all charged substances across the membraneg. Inside cell is negative- membrane potential favors the passive transport of cations (+) in to the cell & anions (-) out of the cellV. Electrochemical Gradienta. Two combined forces drive the diffusion of ions across a membrane:i. Ion’s concentration gradient- chemical force ii. Effect of the membrane potential on the ion’s movement- electrical force b. Passive diffusion- ion moves down its electrochemical gradienti. Includes concentration, as well as charge across membranec. Examplei. Resting nerve cell: [Na+] lower inside cell than outii. Stimulated- gated Na+ channels open upiii. Na+ ions “fall” down electrochemical gradient1. Driven by concentration gradient of Na+2. Driven by the attraction of cations to the negative interior of the cell (charge)VI. Electrogenic Pumpa. Membrane proteins contribute to membrane potential (difference of voltage across the membrane)b. Sodium-potassium pump- pumps 3 Na+ ions out for every 2 K+ ions pumps in i. Net transfer of +1 charge to extracellular environmentii. Stores energy in form of voltagec. Electrogenic pump (proton pump)- transport protein that generates the voltage across a