BIO 172 1st Edition Lecture 10 Outline of Last Lecture I. Enzymes ContinuedII. CarbohydratesOutline of Current Lecture I. LipidsII. MembranesCurrent LectureLipids:Four kinds of Lipids for this class: Fatty Acids, Triglycerides, Phospholipids, and other Lipids.All lipids are hydrophobic, so this physical property is how we determine what moleculesare lipids. (Lipids do not have the same repeating chemical structure).Sugars, for example, all have a repeating similar structure.Lipids store a lot of energy, and release a lot of energy when broken down. They are mostly composed of hydrocarbon. Lipids are hydrophobic. Lipids are used for fuel storage, membranes, and hormones.Carbons bound to H are hydrocarbon. Saturated means it has all the H, and no double bonds.Lipids are not water-soluble!Unsaturated lipids have double bonds, because there are not enough Hydrogens to bond to the Carbon… so carbon and carbon will have a double bond between them.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.Lipids are NOT water-soluble because lipids are hydrophobic for the most part.The abundance of double bonds (unsaturated) determines fluidity of the membrane. Butter: solid at room temp. Butter has single bonds between carbons, which pack tightly. Even at warm temps, they maintain a solid shape. VanDerWaals forces keep it together. C-C single bonds, because there are enough hydrogen!Unsaturated: olive oil. Can pack if cooled, but room temperature keeps it liquid.*Unsaturated has a bent shape. This means unsaturated fatty acids in a membrane cannot pack as tightly.Saturated moleculescan pack tightly and are held together byVan der waals forcesso because they are straight, they have less fluid membranes.When a membrane is built from fatty acids. . .Fatty acids are held together by glycerol. They go through synthesis (a condensation/ dehydration reaction) where an ESTERLINKAGE forms between glycerol and a fattyacid. Fatty acids linked to glycerol give us a triglyceride.Phospholipids: similar structure totriglycerides, but a phosphate-containingcompound replaces one of the fatty acids.The Polar Head on a phospholipid is HYDROPHILIC. Polar, phosphate, and glycerol group are polar!The non-polar tail of a phospholipid is HYDROPHOBIC.Phospholipids assemble into lipid bilayers.Major hydrophobic group!! Carbon and Hydrogen want to sit IN the membrane. The cholesterol inserts in the membrane to keep it pretty stiff.Cholesterol is a precursor to sex hormones.Hydrophilic portion is small, the polar part that interacts with water. A hydroxyl (H-O) group.Cholesterol makes up animal membrane lipids. Cholesterol provides rigidity at normal to high temperatures. But at low temperature, it increases fluidity of a membrane. Cholesterol inserts itself into animal membranes, and because its hydrophobic part is within the bilayer, the bilayer becomes more tightly packed.Cholesterol is a steroid that helps stabilize the membrane.What can cross a Membrane? Size and charge affect the rate of diffusion across a membrane.Small, nonpolar can cross pretty well! (N2 can make it through).Small, uncharged polar molecules (can make it, a bit more challenging)Uncharged yet POLAR: larger than water or glycerol, like glucose/sucrose can’t make it.Ions: they are small, but they carry a charge. So they cannot make it through the membrane on their own.A “flip flop” does not happen often because the polar head groups on the outside don’t like to move through the membrane.Unsaturated is more fluid, Saturated is LESS fluid!If you insert cholesterol, it reduces fluidity of animal cell membrane!Proteins can be amphipathic. Polar amino acids in a protein are hydrophilic because they have a charge.Non-polar amino acids are hydrophobic, so they can fit within the hydrophobic layers in a membrane. Amphipathic proteins can integrate into lipid bilayers.INTEGRAL MEMBRANE PROTEIN: spans length of protein. From the cytoplasm (where the hydrophilic head sits) to the extracellular portion of the cell (where the other hydrophilic head Lateral movement(~107 times per second) Flip-flop(~ once per month)FluidViscousUnsaturated hydrocarbontails with kinksSaturated hydro-Carbon tails(a) Movement of phospholipids(b) Membrane fluidity(c) Cholesterol within the animal cell membraneCholesterolsits). Spanning the membrane at all is however many it times it goes all the way through.PERIPHERAL: hydrophobic anchors in protein, doesn’t go through protein. Integral membrane protein goes through the membrane but the parts associated or attached to it do not continue through the membrane… so it this type of protein is not considered integrated, rather it is calledperipheral. *** You do not expect to see DISULFIDE LINKS between Cysteine R-groups and the hydrocarbon tail of the lipid, when a integral protein inserts into the membrane.***What best describes how the structure of a phospholipid determines the biochemical natureof a lipid bilayer?Answer: The fact that Phospholipids have hydrophilic heads and hydrophobic tails.Transport through a Membrane:Passive: Simple diffusion, where molecules move from areas of high to low concentration, through the plasma membrane.Facilitated diffusion, where molecules move through the plasma membrane using a protein pore. This protein pore is specific for one type of molecule.Active: Primary, where ATP is used as energy to move molecules against their concentration gradient (so from low to high rather than what they want to do- high to low).Secondary, molecules move using energy from the charges around a cell. (Negative inside cell, positive Hydrogen protons around it.Water moving by Osmosis is a special case of Facilitated Diffusion: Movement of water through an aquaporin (hydrophilic insides of this channel Protein interact with water!) (The outside of the channel Pore is hydrophobic so the pore can interact with the membrane). Facilitated by protein, not using energy!Three functions of Cell Membranes: Permeability Barrier to prevent leakage and function as a gateway for transport of nutrients intoand out of cell. So simple diffusion will not work for every molecule!Protein Anchor the site of many proteins involved in transport.Energy Conservation where the proton motive force helps move molecules with