Test 3 Review Sheet

Test 3 Review Sheet - Exam 3 Review Sheet *This is what I...

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Exam 3 Review Sheet *This is what I think is important from the chapters. Dr. Rothschild has not looked at this and it may not be all inclusive of questions that may appear on the test. * At the end of each chapter there is a page called essential concepts: I think these are very helpful in picking out the main ideas of each chapter. I think the book has very good figures to explain certain concepts and I have indicated which figures I think are most helpful/most important. Don’t ignore the details but focus on big picture stuff and how things fit together. Chp 11 Membrane Structure The lipid bilayer – its structure leads to a variety of its specific and important functions o It acts as a selective barrier: it keeps things separate both from the cell and the outside world and within the cell. A good example is a lysosome: it keeps degrading enzymes away from the rest of the cell so it doesn’t digest itself. Membranes allow of different organelles to have different functions o Membranes are important in receiving info, importing and exporting molecules, and movement and expansion o Phospholipids have a hydrophilic head and a hydrophilic tail which makes them amphipathic (you should know this already!!!) Hydrophilic = likes water/ water soluble, has charged groups and these are distributed unevenly Hydrophobic = hates water/ insoluble, organizes water around itself like a cage (11-9). o Figure 11-6: basic structure o There are a variety of types of phospholipids, they differ in the head groups attached to the phosphate group. Ex: phosphatidylserine and phosphotidalinosotal) o Because phospholipids are ampiphatic they form a bilayer to minimize energy o Liposome = pure phospholipids in water o Phospholipids move We know this because of experiments in artificial bilayers: FRAP experiment (11-36) Lipids move readily within their ½ of the bilayer (lateral diffusion) Lipids rarely move across the ½: this requires the enzyme flipase Lipids can also rotate and flex This motion is what makes the bilayer fluid and is crucial to its function, the amount of fluidity depends on composition and is affected by packing o Hydrocarbon tails Length and the number of double bonds both influence packing. Shorter decreases fluidity Double bonds make it harder to pack o Cholesterol influences fluidity, it makes the bilayer more stiff by filling in between phospholipids (one of the reasons we need some cholesterol in our diet) o Fluidity is important
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Enables protein diffusion Proteins and lipids can move to other regions of the cell Membranes can fuse together Molecules can distribute evenly o The bilayer is asymmetrical o Membranes are made in the ER and bud off to form vesicles that then incorporate into other structures Fig 11-19 o Orientation is preserved within the bilayer relative to the cytosol, the cytosolic side always faces the cytosolic side Membrane proteins o 50% of the membrane mass
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This note was uploaded on 11/29/2011 for the course BIO 218 taught by Professor Rothschild during the Spring '11 term at VCU.

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Test 3 Review Sheet - Exam 3 Review Sheet *This is what I...

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