What are some of the common features of eukaryotic cells What about prokaryotic cells BSCI330 REVIEW EXAM 1 Cells and viruses Dynamics of Biomembranes List four different classes of eukaryotic cells Plant Animal Protists Fungi Eukaryotic o Plasma membrane o Cytoplasm o Chromatin o Membrane bound organelles o Multiple linear chromosomes with histones o Nucleus o Nuclear envelope o Larger in size o Single circular chromosomes no histones o No nucleus o Smaller in size o Cytoplasm Prokaryotic Describe the structure and composition of a retrovirus virus RNA containing virus that replicates in a cell by first making an RNA DNA intermediate and then a double stranded DNA molecule that becomes integrated into the cell s DNA The term retrovirus refers to the virus ability to reverse the usual flow of genetic info which normally is from DNA to RNA GP 120 coat protein RNA Reverse transcriptase Capsid Envelope Lipid bilayer Contain 2 RNA molecules Glycoproteins Assembled with structural protein Outline the replication cycle of HIV 1 Fusion of HIV to host cell by CD4 and CCR5 service proteins that the virus recognizes and binds to before entering the cell 2 HIV RNA reverse transcriptase integrase and other viral proteins enter the host 3 Viral DNA is formed by reverse transcription 4 Viral DNA is transported across the nuclear envelope and integrates into the host 5 New RNA is used as genomic RNA to make viral proteins 6 New RNA and proteins move to cell surface and a new immature HIV virus 7 The virus matures by protease releasing individual HIV proteins cell forms DNA by integrase What are the major protein products encoded by the HIV genome and what are the functions of the proteins in the life cycle of the virus GAG matrix capsid nucleocapsid POL cleaved into 4 parts protease integrase polymerase reverse transcriptase RNAase ENV cleaved into 2 parts that become part of the envelope With one sentence indicate the contributions to cell biology by each of the following individuals Robert Hooke 1663 focused light on an object looked at a cork under a microscope saw cells and distinguished and named cells for the first time helped in plant cell wall Anton Van Leeuwenhoek created small microscope and observed lake water discovered organisms in it red blood cells sperm insects Peyton Rous found fibrosarcoma Irving Langmuir theorized that oils consisting of an aliphatic chain with a hydrophilic end group perhaps an alcohol or acid were oriented as a film one molecule thick monolayer of oil upon the surface of water with the hydrophilic group down in the water and the hydrophobic chains clumped together on the surface The thickness of the film could be easily determined from the known volume and area of the oil as area becomes smaller layer will exert pressure Gorter and Grendel the founding fathers of our current model of plasma membrane structure predicted that if a plasma membrane were really a bilayer then its surface area should be half that occupied by all its amphipathic lipids spread out in a monolayer o Hydrocarbon tails 30A o Polar ends 15A Davson and Danielli The fluid mosaic model expanded on the Davson Danielli model by including transmembrane proteins and eliminated the previously proposed flanking protein layers that were not well supported by experimental evidence Singer and Nicolson 1972 how proteins are positioned in membranes lipid bilayer structures fluid mosaic model Linus Pauling found the alpha helical structure What is meant by a unit membrane Give an illustration for how the membrane would look under the electron microscope What about under the light microscope Approx 60 80 angstrum A which is equivalent to 6 8 x 10 10 meters All have a rail road like structure All membranes have it What are the major constituents of biological membranes of eukaryotic cells Proteins 50 Carbohydrates 10 Lipids mostly phospholipids fatty acid phosphate group gylcerol 40 Give the structure and name of a saturated fatty acid Show the structure of the fatty acid when it is unsaturated cis double bond in center of unsaturated causing it to kink just a carboxillic acid and a fatty acid chain What are the constituents of a phospholipid Draw the structure and label the constituents of a phospholipid Fatty acids phosphate group glycerol kinks R group Define each of the following terms Amphipathic contains both hydrophilic and hydrophobic Hydrophobic inside of a lipid bilayer doesn t like water nonpolar Hydrophilic outer part of a lipid bilayer likes water polar Draw the structure of cholesterol and indicate why the molecule is amphipathic Amphipathic because it has a polar head steroid rings and non polar hydrocarbon How do we know that the plasma membranes of red blood cells consist of a bilayer of phospholipids Briefly outline the history behind this conclusion and or how you would design an assay to confirm the conclusion o Gortel and Grendel 1925 used acetone to extract lipids from RBCs Knew surface area of RBCs Placed extract on trough and measures monolayer surface area Cell surface area showed double of monolayer demonstrating bilayer structure Provide a diagram and a brief description of the fluid mosaic model of the structure of biological membranes What was the experimental basis for the original proposal The plasma membrane is described to be fluid because of its hydrophobic integral components such as lipids and membrane proteins that move laterally or sideways throughout the membrane The membrane is depicted as mosaic because like a mosaic that is made up of many different parts the plasma membrane is composed of different kinds of macromolecules such as integral proteins peripheral proteins glycoproteins phospholipids glycolipids and in some cases cholesterol lipoproteins plasma membrane is a lipid bilayer interspersed with proteins It is so because of its phospholipid component that can fold in itself creating a double layer or bilayer when placed in a polar surrounding like water Original basis the standard model for membrane structure the Davson Danielli Roberston DDR model was a bilayer of lipids between two monolayers of unfolded protein Each protein layer faced an aqueous environment cytoplasm or interstitial fluid depending upon whether the membrane enclosed an organelle or the cell itself o Singer and Nicholson thought the proteins were lateral and came up with fluid mosaic model Outline the freeze fracture freeze etch method used to examine the structures of biomembranes
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