BIOL 213 1st Edition Lecture 7 Outline of Last Lecture I. Review of protein structure levelsII. Enzymesa. Basic overviewIII. Regulation of Enzymesa. Regulation is essential to a working cellb. Can be positive or negativeIV. Inhibitorsa. Turn an enzyme “off”b. Negative regulationc. Competitive inhibitorsd. Noncompetitive inhibitorsV. Activatorsa. Turn an enzyme “on”b. Positive regulationVI. Phosphorylationa. Add a phosphate group to an amino acid of a proteinb. Changes the structure of the protein, therefore its functionc. Can be negative or positive regulationThese 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.VII. GTP-proteinsa. GTP turns the G-protein “on”i. Positive regulationb. GDP turns the G-protein “off”i. Negative regulationVIII. Molecules can bind in the right order to cause movementa. Motor proteinsIX. Coordination of regulation of enzymesa. This creates metabolic pathwaysX. Evaluating and graphing enzyme performancea. Graph: substrate concentration vs the rate of substrate consumptionb. Vmax and KM c. Brick wall analogyd. How enzyme regulators affect enzyme performancei. Competitive inhibitors1. Vmax = no change2. KM = increasedii. Noncompetitive inhibitors1. Vmax = decreased2. KM = no changeiii. Activators 1. Vmax = increased2. KM = no changeOutline of Current Lecture I. Cell membranea. Basic overviewII. The cell membrane is a lipid bilayera. Fluid mosaic modelb. Liposome formationIII. Fluidity of the membranea. How lipids move within the membraneb. Things that affect fluidityIV. Membranes are asymmetricala. Each layer of the membrane is unique in its compositionb. How this is accomplished i. Flipase V. Membrane proteinsa. Different functionsb. Different associationsc. Mobility VI. Detergentsa. Useful for studying integrated proteinsVII. The cell’s surface is coated with carbohydratesa. Lubricantb. Cell-cell signalingCurrent LectureI. Cell membranea. All are selectively permeable barriersb. They control what goes in and what goes out of the cellc. Compositioni. Lipids1. Phospholipidsa. Most abundant2. Glycolipidsa. Sugar part of head group3. Sterols a. Ex: cholesterolb. All are amphipathic because they’re inserted into the membrane in a way similar as the phospholipidsii. Proteins 1. Integrala. These proteins are directly attached to the membrane2. Peripherala. These proteins are loosely associated with the membraneiii. There’s an almost even distribution of proteins and lipidsII. The cell membrane is a lipid bilayera. Fluid mosaic model – i. The membrane is a fluid bilayer made of lipids and proteinsb. It has a hydrophilic exterior and hydrophobic interior due to the hydrophilic heads and hydrophobic tails of the phospholipidi. Any lipid layer naturally forms a sphere in an aqueous solution so that no hydrophobic region is exposed to water1. There are no corners or edges which would expose the hydrophobic interior c. The formation of a sphere is spontaneous for all lipids i. No biology is included in the formation of the sphereii. Biology is only included in determining the function of the membraneiii. The sphere is known as a liposome1. Compared with micelle:2. Micelle is monolayered so that the inside is lined with hydrophobic fatty tails, whereas a liposome is bilayered so that the inside is lined with hydrophilic heads3. It allows an aqueous solution to be on the inside of the liposomea. i.e. a cellIII. Fluidity of the membranea. Lipids (natural, spontaneous movements)i. Lateral diffusion1. Lipids can move side to side within the same leaflet (one layer of the membrane)ii. Flexion1. The fatty acid chains can move apart from each other, like scissors,due to thermal energyiii. Rotation1. Lipids can spiniv. Never (for the sake of this class) flip-flopping1. Lipids cannot just flip to the other leaflet2. This would expose they hydrophilic head to the hydrophobic interior – biology doesn’t like thata. Hydrophilic things like hydrophilic placesb. Hydrophobic things like hydrophobic placesc. They don’t like to comingle b. Things that affect the fluidityi. Fatty acid chain length1. Short = more fluid2. Long = less fluidii. Saturated vs unsaturated fatty acid chains1. Unsaturated = more fluid2. Saturated = less fluidiii. Sterols1. Cholesterol in saturated lipids = more fluid2. Cholesterol in unsaturated lipids = less fluida. Fills the space between the kinked fatty acid tailsiv. Temperature 1. Higher = more fluid2. Lower = less fluidIV. Membranes are asymmetricala. Each leaflet is unique in the composition of its lipidsi. Leaflet = one layer of the bilayer ii. The leaflets are unique because each one is exposed to different environments, therefore their functions are different, which requires different structures (kinds of lipids)1. The different distribution of phospholipids and glycolipids creates different surfaces with different structuresb. Asymmetry is established during synthesis in the ER and the enzyme flipase flips the lipids so that they’re on the right sidei. Lipids are always synthesized and then added to the cytosolic side of the ER membraneii. If the lipid needs the be on the other side of the bilayer, flipase flips it over to the other side1. It needs an enzyme to do this because remember that lipids neverspontaneously flip to the other side of the membrane2. Each kind of lipid has its own kind of flipase3. Lipids that don’t have to be flipped to the other side of the membrane don’t have a flipasec. When a vesicle is made from a membrane-bound organelle, travels to the cell membrane, and then fuses with the cell membrane, the sidedness of the lipids DOES NOT CHANGEi. For example, if a vesicle is formed from the ER (after the flipase has put all of the lipids on the correct side), the lipids on the cytosolic side of the ER will remain on the cytosolic side of the vesicle and will continue to remain on the cytosolic side of the cell membraneV. Membrane proteinsa. They have several different functionsi. Transporters1. There are ones that use energy and ones that don’tii. Anchors1. These can constrain molecules to a specific area, maintain the membrane integrity, etc.iii. Receptors1. The ligand binds to the extracellular part of the protein which causes a conformation change2. This conformation change carries the message to the inside of the cell that something is bound to the receptor.3. And then a reaction takes