Quiz 1 Material Lipids Membranes Permeability Transport Channels Membrane Poten9al Receptors as Channels GPCRs RTKs Phosphoinosi9des PIPs Lipid Bilayer Proper4es spontaneous forma9on asymmetry membrane uidity Fluid Mosaic Model Predic9ons lipid is in bilayer form integral peripheral proteins are associated w membrane lipid protein are free to di use transla9onally rota9onally Evidence osmo9c change cells shrink swell electron microscopy xLray di rac9on FRAP asymmetry of lipids protein Modi ca9ons some lipids do not di use freely are instead restricted by cell junc9ons or interac9ons w cytoskeletal laments on cytoplasmic side of membrane Membrane Func4ons barrier separa9ng compartments controls passage of material receives transmits info physical plane What is the endosymbiont hypothesis for the origin of mitochondria Evidence early euk cells lacking mitochondria engulfed early aerobic proks rather than digest these proks early euks formed symbio9c rela9onship w early proks euks o ered nutrients shelter while acquiring very e cient energy systems evidence based on characteris9cs of mitochondria have circular DNA lack histones have smaller prok Ltype ribosomes start protein synthesis w fLMet protein synthesis inhibited by chloramphenicol not cycloheximide have double membrane Describe the nature of a hydrogen bond how it a ects the structure of molecules in cells HLbond strength 5 kcal mol weak H2O HLbonds w 4 other H2O molecules tetrahedral orienta9on greatest strength preferred orienta9on HLbonds form a straight line temp Lsensi9ve very shortLlived coopera9vity drama9c changes in structure uidity cause forma9on of Lhelices Lsheets List weak chemical bonds or forces found in proteins explain how they a ect protein conforma4on electrosta9c interac9ons primary folding AA sequence a rac9on of L charges to one another HLbonds secondary folding Lhelices Lsheets determine helical or sheet shape of protein hydrophobic interac9ons ter9ary folding domains L Lfolds nonLpolar side chains fold inward polar side chains fold outward dipole interac9ons structure protein structure quaternary folding assembly of mul9ple pep9des to form na9ve covalent bonds are stronger than nonLcovalent bonds thus stabilize Describe 2 major methods regarding how cells u4lize energy provided by nucleo4de triphosphates to control protein conforma4on Signaling via GTPOBinding Protein 1 GEF signals inac9ve GTPLbinding protein to change binding partner from GDP to GTP 2 GDP dissociates 3 GTP binds protein ac9va9ng 4 GAP tells GTPLbinding protein protein to turn o 5 GTP is hydrolyzed to GDP inac9va9ng protein Signaling via Phosphorylated Protein 1 Protein kinase phosphorylates target protein 2 Phosphate molecule protein experience a covalent bond 3 Protein ac9vated 4 Phosphatase cleaves phosphate inac9va9ng protein A scien4st tested the binding of molecule X to X receptor in mice made a Scatchard plot as shown A is the plot from WT mice B is the plot from mutant mice Explain the possible defect in the mutant mice by comparing B to A steeper slope larger Ka smaller Kd higher a nity Since plot B has a more gradual slope compared to that steep slope of plot A mutant mice must have a lower a nity for bound ligand than WT mice Note L concentra0on of free ligand at equilibrium What kind of lipid can form the bilayer Why Diacyl phospholipids cannot t in micelles b c heads are too far apart due to double tails Thus diacyl phospholipids form lipid bilayer Fa y acids or monoacyl phospholipids form micelles How long would it take for a molecule of hemoglobin to move from your heart to your foot if there was no circula4on movement was only via di usion Hemoglobin is a protein proteins cannot di use through membrane Hemoglobin cannot move from your heart to your foot w no circula9on movement only occurring via di usion This will never happen w o a carrier to help transport the hemoglobin
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