A. A lot more internal membrane than plasma membrane, plasma membrane only accounts for about 2—5% of the total membrane in the cell – rest is in cell making up organellesB. Structure1. Lipid bilayer, (4-5nm in diameter)- lipids are about ½ the mass of the plasma membrane, is hydrophobic in the core and hydrophilic in the outside of cell and inside the cell, has lipids:a) phospholipids- head: C-C-P-choline, or serine or ethanolamine, or inositol(ex. phosphotidylcholine)–differ in terms of structure and in terms of distribution, choline is on the outside of cell and the rest are on the cytoplasmic monolayer – then Tail: attached to head are 2 carbon chains(1) phospholipids are the largest contingent component of the membrane(2) in the absence of other molecules, usually is a slight electrochemical gradient across membrane due to the unequal distribution of phospholipids it is positive on the outside and negative on the inside naturally, without alteration- because of this other molecules, particularly proteins recognize this charge difference and fit into this membrane in a specific area(a-symmetrical distribution)(3) phospholipid tails: normally one is saturated and the other is unsaturated in phospholipid tails(4) phospholipids tail: is 14-24 carbons in length, there is some flexibility to this(a) the fluidity in our membranes doesn’t matter so length doesn’t matter too much for homeotherms like us(5) semi-permeable, flexible and dynamic changing in shape and fluidity (phospholipids look like butter) – Our homeotherm body structure allow our plasmamembranes to be fluid, other ectotherms and polkilotherms can alter the fluidity of their membrane(a) Can alternate fluidity of membrane in 2 ways: (fluid membrane is much less selective of what goes through it, and rigidity would let much less through)(b) Shorter fatty acid chains- the shorter the fatty acid, the more fluid the membrane – the longer the fatty acids will attract each other and intertwine to make the membrane more rigid(i) can adjust the number of carbons in their membrane through a process of lipid synthesis that will be made and replace the phospholipids bilayer(ii) the thickness of the membrane is not changing, but the length of the tails are changing, clogging the middle of the membrane up more with longer tails(c) Altering saturation/unsaturation- one double bond adds a kink in the chain, the more unsaturated fatty acids the more fluid the membrane gets because they can not pack together as well.(i) By increasing unsaturation, the membrane becomes more fluid(6) phospholipids spin and move through their monolayer of the bi-layerb) cholesterol (do not have to know specific structure) know that it is 4 planar rings and attached to the 4th ring is a hydroxyl fatty acid or hydrocarbon (this part is a little hydrophobic and the rings are a little more hydrophilic)(1) essential component of the cell membrane(2) cholesterol is in the monolayers of the phospholipids, stuck in there and surrounded by phospholipids(3) the more cholesterol decreases movement and fluidity- slows down movement of the phospholipid (stericly inhibits them)(a) has to insert the perfect amount of cholesterol to make the perfect fluidity in the membrane(b) cells regulate the amount of cholesterol in the membranec) glycolipid- made by phospholipid with an oligosaccharide attached to it (short, highly branched polysaccharide, composed of 3-20 monosaccharide)(1) most asymmetrically distributed in membrane – ONLY found on the outer monolayer of the plasma membrane(2) looks like a receiving antenna – their function is actually to receive signals, - they are the principle way they can recognize different cells and differentiate cells(a) when these screw up, we see problems, loss of ability of cells to recognize other cells causes metostatic cancer.(3) Also found around many nerves as a glycolipid called myelin (that increases the speed of an action potential)2. Proteins in Membrane (other ½ of plasma membrane) – very important in cell signalinga) one protein for every 50 lipids because they are much bigger in size, one protein to 50 lipids is about equal in massb) 2 Types of proteins(1) Peripheral – schematically on one monolayer or the other(a) anchored by alpha helix usually, since it is hydrophobic in nature (or some other hydrophobic part of the protein is used) to anchor in the hydrophobic tails and then spew outside the membrane(b) or can have proteins covalently bound to a fatty acid making a lipoprotein to stick out on one side or the other(c) finally can be bound by weak bonds to each other outside the membrane(d) some are enzymes, some are gates, channels etc.(2) Transmembrane – structurally span entire membrane (domain on outside, transmembrane domain and a domain on cytoplasmic side)(a) transmembrane domain - usually beta sheet or alpha helix(b) stimulation on one side or the other is usually interpreted on the other side(c) can have proteins that look like they are sewed back and forth, with domains up and down the membrane, spanning the whole membrane(i) some proteins are sown like this in a circle to make a pore to allow large molecules to go from one side of the membrane to anotherc) can add an oligosaccharide to the protein (glycoprotein) to help the cell signaling, allowing the cell to communicate with other cells(1) receives information on the outside of cell and transduces it on the insideBY 330 1st Edition Lecture 14 Outline of Last Lecture I. Protein Synthesis/ TranslationA. 3 processes: Initiation, Elongation, TerminationB. InitiationC. ElongationD. TerminationOutline of Current Lecture II. Plasma membraneA. A lot more internal membrane than plasma membraneB. Structure Current LectureII. Plasma membraneA. A lot more internal membrane than plasma membrane, plasma membrane only accounts for about 2—5% of the total membrane in the cell – rest is in cell making up organellesB. Structure1. Lipid bilayer, (4-5nm in diameter)- lipids are about ½ the mass of the plasma membrane, is hydrophobic in the core and hydrophilic in the outside of cell and inside the cell, has lipids:a) phospholipids- head: C-C-P-choline, or serine or ethanolamine, or inositol(ex. phosphotidylcholine)–differ in terms of structure and in terms of distribution, choline is on the outside of cell and the rest are on the cytoplasmic monolayer – then Tail: attached to head are 2 carbon chains(1) phospholipids are the largest