BIOL 1441 1st Edition Lecture 11 Outline of Last Lecture I. OrganellesII. CytoskeletonIII. Extracellular componentsOutline of Current 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 Current LectureI. Plasma Membranea. Boundary that separates living cell from its environmentb. Selective permeability- allowing some substances to cross it more easily than othersThese 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.i. Selective based on chemical propertiesc. Cellular Membranesi. Composed of lipids(mostly), proteins, carbohydrates1. Phospholipids- most abundant lipid in the plasma membraneii. Amphipathic molecules- containing hydrophobic & hydrophilic regionsd. Fluid Mosaic Modeli. Membrane is a fluid structure with a “mosaic” of various proteins/phospholipids embedded in ite. Fluidity of Membranesi. Phospholipids in the plasma membrane can move within the bilayer (fluid as salad oil)1. Held in place by hydrophobic interactions (weak)ii. Lipids, (some proteins), drift laterallyiii. Rarely- molecule flip-flop across the membraneiv. As temperatures cool, membranes switch from a fluid state to a solid state1. Molecules start slowing down and pack tightly together into a solidv. Temperature where membrane solidifies depends on types of lipids (fatty acids)vi. Membranes rich in unsaturated fatty acids are more fluid at lower temperature than saturated fatty acids1. CANT FORM SOLID IF IT INCREASES UNSATURATED FATS B/C OF KINKS IN THE TAIL2. UNSATURATED FAT: CARBON TO CARBON DOUBLE BONDS (KINKS IN TAIL)f. Cholesteroli. Cholesterol (steroid) - effects membrane fluidity depending on the temperature ii. Warm temperatures- restrains movement of phospholipids, making themless fluid1. MOLECULES HAVE A LOT OF KINETIC ENERGY; CHOLESTEROL ACTS AS A SPEED BUMP AND SLOWS THE MOLECULES DOWNiii. Cool temperatures- maintains fluidity by preventing tight packing1. CHOLESTEROL INSERTS ITSELF BETWEEN TAILS TO KEEP THEM FROM PACKING TOO TIGHTLY (FROM FORMING A SOLID) TO MAINTAIN FLUIDITY2. Lowers the temperature required for a membrane to solidifyII. Membrane Proteinsa. Proteins in the plasma membrane can moveb. Different types of cells have different types of proteins in their plasma membranec. Integral protein- penetrate the hydrophobic core of the lipid bilayeri. Transmembrane protein- spans the entire membraneii. INSERTS ITSELFd. Peripheral protein- not embedded in the membrane, bound to iti. CAN BE ATTACHED TO A PROTEIN OR A PHOSPHOLIPIDe. 6 Major Functions of Membrane Proteinsi. Transportii. Enzymatic activityiii. Signal transductioniv. Cell-cell recognition- all cells in your body have markers that identify that it is you1. Cells recognize each other by binding to surface molecules2. Recognize self vs non-self (pathogens, transplant tissue)3. Surface molecules usually carbohydrates a. Covalently bonded to lipids- glycolipids(glycol-tiny sugar attached to, lipids- a big lipid)b. Covalently bonded to proteins- glycoproteins4. Markers on your blood cellsa. Type A, B, AB or Ov. Intercellular joiningvi. Attachment to the cytoskeleton and ECMIII. Permeability of the Lipid Bilayer- SIZE/CHARGE ARE IMPORTANTa. Hydrophobic (nonpolar) molecules- dissolve in the lipid bilayer & pass through the membrane rapidlyi. O2, CO2, hydrocarbonsii. Hydrocarbons-nonpolarb. Hydrophilic (polar) molecules- do not cross the membrane easilyi. Sugars (glucose), ions, waterii. CROSS THROUGH MEMBRANE PROTEIN (B/C POLAR AND BIG MOLECULES CANT MOVE THROUGH FAST ENOUGHc. Transport Proteinsi. Allow passage of hydrophilic substances- very specificii. Channel proteins- hydrophilic channel that specific molecules or ions can use as a tunnel1. Opens up to let It in and shuts after-pore2. Aquaporins- facilitate the passage of wateriii. Carrier proteins- bind to molecules and change shape to shuttle them across the membrane1. Attaches to molecule and drops it off on the other side of membraneIV. Types of transporta. Passive (diffusion): high to low (natural)i. Channel proteins1. Aquaporin or ion channelii. Carrier proteins iii. HYDROPHOBIC SUBSTANCES DIFFUSE RIGHT ACROSS MEMBRANE. DON’T NEED TRANSPORT PROTEINS b. Active: low to high (not natural, have to use energy)i. ONLY carrier proteinsc. Passive Transport- Diffusioni. Thermal motion (heat)- movement of moleculesii. Diffusion- molecules spread out evenly into the available space- NATURALMOVEMENT OF ANYTHING FROM HIGH TO LOW CONCENTRATION (DOESN’T HAVE TO BE ACROSS A MEMBRANE)1. Each molecule moves randomly (Brownian Motion)a. EVERYTHING HAS MOVEMENT2. All the of molecules- movement in one directioniii. Molecules move HIGH concentration to LOW concentration1. Equally spread throughoutd. Factors that Affect Diffusion-AFFECTS THE RATE OF DIFFUSIONi. Heat: increase heat, increase molecular collisions, increase diffusion rate1. Direct relationshipii. Size: smaller molecules move faster than larger molecules, smaller molecule will diffuse faster1. Inverse relationshipiii. Concentration gradient: steeper gradient, faster diffusion1. Direct relationship2. Concentration Gradient- the difference in concentration of a substance from one area to anothera. Moves HIGH to LOWiv. Passive transport- requires no energy from the cell to make it happenv. Only happens in a cell if the substance can readily cross the plasma membranevi. Water can diffuse across the cell membrane through aquaporins (hydrophilic channels)vii. Diffusion refers to the movement of SOLUTE (molecules) down its OWN concentration gradient1. Do NOT confuse this with osmosis- the diffusion of WATER (solution)viii. Osmosis- diffusion of water across a selectively permeable membrane1. Water is diffusing on its OWN concentration gradienta. From a high to low concentration2. Water diffuses across a membrane- from an area of low solute concentration (high water) to an area of high solute concentration (low water)3. WATER WILL ALWAYS FLOW TO A HIGH SOLUTE CONCENTRATION (LOW WATER CONCENTRATION)e. Tonicityi. Ability of a solution to cause a cell to gain or lose waterii. Isotonic solution: solute concentration is the same as that inside the cell; no net water movement across the plasma membraneiii. Hyper tonic solution: solute concentration is greater