BS 161 1st Edition Lecture 9 Outline of Last Lecture I Lipids and membranes Outline of Current Lecture II Finish membranes Current Lecture Double bonds cause links in phospholipid tails which is why unsaturated fat tails are more fluid than saturated fat tails Steroids built from cholesterol non protein hormones examples are estrogen and testosterone Membrane structure fluid mosaic model they can move around Integral proteins embedded in bilayer go all the way through Peripheral proteins attached to the surface still embedded slightly but don t go all the way through Fluidity varies with phospholipid and cholesterol composition The less packed together the tails are the more the membrane and proteins can move around laterally Cholesterol increases fluidity and lowers the temperature at which the membrane can solidify tails cant pack as tightly if there are cholesterol molecules The more fluid the membrane is the more permeable it is allows molecules to get across membrane Functions of plasma membrane proteins 1 Transport small molecules ions water 2 Enzymatic activity the shape of some enzymes requires being in a hydrophobic space 3 Signal transduction insulin and its receptor 4 Cell cell recognition important in determining self and non self cells immune system will attack non self cells 5 Adhesion intercellular joining attachment to the cytoskeleton and extracellular Matrix ECM Translation protein synthesis occurs in the endoplasmic reticulum
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