BSCI330REVIEW QUESTIONS – SET 1List 4 different classes of eukaryotic cells. animal plant fungi protistCommon features of eukaryotic cells nucleus nuclear envelope chromatin multiple, linear chromosomes with histones membrane-bound organelles cell division by mitosis or meiosis larger in size cytoplasm plasma membrane different types of organellesCommon features of prokaryotic cells single, circular chromosome, no histones no nucleus smaller in size cytoplasmStructure and Composition of retrovirusDefinition: a retrovirus is an 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 a cell's DNA gp 120 coat protein contains 2 RNA enveloped in lipid bilayer reverse transcriptase glycoproteins assembled with structuralproteinsOutline the replication cycle of HIV1. Fusion of HIV to host cell by CD4 and CCR5 co-receptor proteins. 2. HIV RNA, reverse transcriptase, integrase, and other viral proteins enter the host cell.3. Viral polymerase makes RNA ---> DNA by the enzyme reverse transcription.4. Viral DNA binds to integrase and integrase brings DNA across nuclear envelope and inserts DNA into chromosome/DNA of host cell.5. New viral RNA is used as genomic RNA and to make viral proteins.6. New viral RNA and proteins move to cell surface and a new, immature, HIV virus forms.7. The virus matures by protease releasing individual HIV proteins.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? gp120 = an HIV glycoprotein that protrudes from the outer surface of the virion, binds to a CD4receptor on a T cell to facilitate entry of viral nucleic acid and proteins into the cell GAG = all structural to help make it foldmatrix – lines envelopecapsid – protects corenuclear capsid – protects genome POL = integrase – integrates DNA into chromosome of host cell protease – cleavage of GAG protein to help virus maturationviral polymerase reverse transcriptase – RNA → DNARNase – degrades RNA ENV = cleaved into 2 pieces that become part of viral envelopeIndividual contributions to cell biology:Robert Hooke: looked at cork under microscope and found celluli and separately found mucoi (a type of fungus)Anton Van Leeuwenhoek: created a small microscope, observed lake water, red blood cells, sperm, and insects. In lake water he found microorganismsPeyton Rous: injected fibrosarcoma into healthy chickens, viruses genome was RNA which encodedinto host DNA and caused cancer, two RNA molecule enveloped in lipid bilayerIrving Langmuir: studied films with monolayer of oil and found that hydrophobic ends stick together, area decrease = pressure increaseGorter and Grendel: surface area of lipid bilayer, hydrocarbon tails are 30 angstrom and polar ends are 15 angstromDavson and Danielli: there model of cell membrane had lipid bilayer with a layer of protein coating on top and bottomSinger and Nicolson: fluid mosaic model, integral proteins embedded into lipid bilayer and peripheralproteinsLinus Pauling: found alpha-helix structure of proteinsUnit Membrane 60-80 angstrom = 6-8 x 10^-10 m all have a railroad like structure concluded that all membranes must have same underlying structuresWhat are the major constituents of biological membranes of eukaryotic cells? 50% proteins 40% lipids = mostly phospholipids made of fatty acids, phosphate groups, and glycerols 10% carbohydratesSaturated fatty acid:Unsaturated fatty acid:KNOW STRUCTURES/CHART:What are the constituents of a phospholipid? fatty acids phosphate group glycerolDefine the following terms: amphipathic = has hydrophobic and hydrophilic constituents hydrophobic = non-polar, doesn't go near water hydrophilic = polar, goes near waterDraw structure of cholesterol- amphipathic because it has polar (hydrophilic) and non-polar (hydrophobic) endHow 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). RBC don't have a nucleus or membrane-bound organelles so any lipids found would have to be in the plasma membrane extract lipids with acetone used Langmuir trough to determine area lipids could cover could measure surface area of RBC so they could calculate total surface area covered by membrane lipid extracted could cover twice the area needed to enclose cells, so double layer of lipidsFluid Mosaic Model- Singer and Nicolson developed this model because they didn't agree with the original model fromDavison and Danielli which stated that there was a protein coaton outside of lipid bilayerOutline the freeze fracture (freeze etch) method used to examine structure of biomembranes andcontrast this with older EM method of examining membranes in sections stained with osmium tetraoxide.Freeze fracture freeze → fracture → vacuum sublimate → platinum carbon replicate of exposed surface is made → dissolve cells → EM in liquid nitrogen cells freeze but if you bring the temperature up slowly then not all cells will die = more cell preservation more ragged surface when slicedOsmium tetraoxide stain tissue → add aldehyde which causes tissues to create bonds → add OsO4 (osmium tetraoxide) stain → embed tissues in plastic like epoxy resin → slice in thin sections → bombard with electrons → flourescent screen under microscope glows when hit with electronsDescribe the various ways by which proteins are anchored to biological membranes and what is meant by peripheral membrane proteins versus integral membrane proteins. proteins bind to lipid bilayer by covalently-linked fatty acids proteins on plasma membrane are glycosylated Peripheral membrane proteins – associated with molecules on membrane surface, but do not penetrate into the membrane Integral membrane proteins – transmembrane segment contains amino acids with hydrophobic side chainsHow are proteins anchored to a membrane via a fatty acid? Show the orientation of the fatty acid and the rest of the protein in relation to the lipid bilayer. protein links to the cytosolic surface of the plasma membrane via covalently attached fatty acid protein binds to membrane
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