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Midterm 1 Oct 17 Chapters 1-7 Key on lectures RCH 101 8:30 – 9:20 40 MC o Computer card o Recognize structures like phosphatidylethanolamine Kin 217 – Oct 7 - [structure of major phospholipids in cell membranes] - Different types of membrane lipids (we talked about this last time) [ chart of Phospholipid composition of organelles ] o Note that sphingomyelin high in plasma membrane [ Inner / Outer membranes - curvature stress - phosphatidyl choline, big methyl group on outer membranes. Which ones on the inside? –those with small head group phosphotidyl serine (?) ] Cholesterol Fig 7.4 o Going to stick into a membrane o Cholesterol doesn’t like to ‘dance’ – it’s a wallflower What is cholesterol doing in membranes? o Prevents close packing o Lowers the melting temperature o Melting transition is less sharp o Animal cell membranes have cholesterol Example – 25% for red cells Plasma membranes have more cholesterol Diagram of Biomembrane structure o [Series of proteins sticking in, sticking on…sea of proteins in membrane] Fluid Mosaic Model o [Like surfing on waves— o Water phospholipids o Surfers some are in it, some on top] Lipid Rafts o [Research is showing that phospholipids AREN’T randomly arranged] o [Microdomains that associate with proteins, domain has its own control…area around lipid very different from other areas] o [Controversial – some people believe in these, some don’t ] Transmembrane Protein Fig 7.7 o Glycophorin 10 amino acids span bilayer Hydrophobic [What controls the hydrophobic and hydrophilic tendencies of an AA? – the residue groups! ] If you see a hydrophilic region on a transmembrane, you know you’ve got some sort of porin Porin o Beta barrel structure Forms a pore Allows a selective small molecule movement Hydrophilic interior [ what’s coming in and out is essential for survival] Peripheral membrane proteins [not actually embedded in bilayer ] o Attachment Hydrogen bonding and ionic interactions in some cases o Anchoring [nice big] hydrophobic fatty acids (14,16 or 18 carbons) Covalently attached to the protein o N–terminal amino acid, via cysteine, via a hydroxy amino acid Fig 7.10 Transport Processes o Passive Transport Simple Diffusion No control [well…indirect control], follows concentration gradient - - - - - - - o o Rate o o o - - Hydrophobicity Ions need to lose hydration [ ions associated with a lot of water molecules…it’s hard to transport such a big molecule] [any thing with a high charge in an aqueous environment has reacted with water..we talked about this last class as well] Passive Transport Facilitated diffusion – requires protein Follow concentration gradient Enzyme like o Specific o Saturable [ can only do so much work before it hits a plateau ] Fast! Transporter – glucose Channel – Na+, K+, Ca2+, Cl-, H2O Gated ion channels o Gated pores or channels Open and close in response to a signal o Ligand Acetylcholine [ it binds and then the gate will open ] o Charge Change in membrane charge Voltage-gated pores Na+, K+ channel Mechanism of the selectivity of the potassium channel (Fig. 7.17) o [ Hydrated sodium is a lot smaller than potassium (?) can’t go into transition stage – requires energy to remove water molecules; won’t react with outside channel groups Transport Processes o Active Transport Requires energy Against gradient [most of the time], larger molecules, cell movement Enzyme like Specific Saturable Slower than channels [facilitated] [ ie: facilitated diffusion is running downhill, active transport -> run uphill ] Primary Use ATP directly Secondary Electrochemical gradient or membrane potential drive transport o Generated by primary active transport o [if you want to get Ca into cell, make cell very negative and it’ll pull Ca into it ] Uniport [one substrate moving across] Active (Ca2+ ATPase) Facilitated Diffusion (blood glucose) Symport [two substrates coming in at different directions] Uptake of one substrate linked with uptake of another Antiport On substrate in, one substrate out Fig 7.2 o [Active transport of sodium by ATP o Sodium brings glucose in as well] Diagram of Movement of solutes across membrane Look at Sodium-Potassium ATP channel… o [ Change in confirmation and moves things across… ] o - Oxygen, carbon dioxide, nitrogen, urea, ethanol, even water [ don’t have to spend any ENERGY to transport oxygen and all those ]