List four different classes of eukaryotic cells.Fungi: food from other organisms, cell walls, filamentous growthYeast: unicellular, budding reproductionProtozoa: unicellular, mostly motile, can live in hostAlgae: unicellular or multi, photosynthetic, simple reproductive systemplants, animals, protists, unicellular algae, fungi What are some of the common features of eukaryotic cells? What about prokaryotic cells?Eukaryotes: membrane enclosed organelles, nucleus, linear DNA w/ histone proteins, 80S ribosome, actin cytoskeletonProkaryotes: no membrane enclosed organelles, nucleoid, cell wall (peptidoglycan), circular DNA w/o histone proteins, 70S ribosomes Describe the structure and composition of a retrovirus.Ex. HIVRetrovirus exists as single-stranded RNA packed into a capsid protein reverse transcriptase: viral RNA is inserted and converted into double strand DNA integrase: works like cut and paste transposon, integrating the DNA into the host, takes doublesstrand DNA through nuclear pore because it contains the necessary nuclear localization signalintegrase cuts 1 chromosome of cell and insert viral DNA into chromosome and re-ligate itThen 3 different genes (gag, Pol, ENV) can be transcribed/translated Outline the replication cycle of a retrovirus, such as the Rous Sarcoma Virus.gag: polyprotein gets cleaved into different structural proteins- capsid, matrix, nucleocapsidPol: cleaved into four parts- viral integrase, protease, polymerase (2 fragments)2 polymeras- reverse transciptase and RNaseENV: codes for the envelope protein, cleaved into 2 fragments of protein What are the major protein products encoded by the genome of a “typical” retrovirus andthe functions of the proteins in the life cycle of the virus? Capsid protein: Reverse transcriptase: Envelope protein:Integrase- requires 4-5 specific nucleotides for insertion, takes the double stranded DNA through the nuclear pore using NUCLEAR LOCALIZATION SIGNAL, cuts 1 chromosomes ofcell and insets viral DNA into chromosome and religates it, shuttle protein uses GTP to move integrase across the envelope Protease- cleaves gag Pol and ENV by doing this makes it infectiousReverse Transcriptase- makes DNA/RNA and then DNA/DNA double helix, RNase dissolves RNA once it has been replicated *Discuss the rationales behind the mechanisms of action of drugs (either available or in development) meant to block the entry of HIV into macrophages. Inhibitors of reverse transcriptase, integrase, protease Summarize the roles (and steps) of HIV gp120 and of gp41 in membrane fusion. How was it discovered that a deletion in the CCR5 gene could affect HIV tropism? Env gene product is gp160 which is cleaved into gp120 and gp41 3 gp120s and gp41s combine in a trimer of heterodimers to form the envelope spike which mediates attachment to and entry into the host cell Gp120- glycoprotein on HIV envelope, plays vital role in attachment to specific cell surface receptors (CD4 receptor)- binding to CD4 induces changes in gp120 and gp41 that lead to fusion of the viral with the hostmembrane CCR5- protein on white blood cells receptor for chemokines (how helper T cells are attracted to specific tissues)HIV uses CCR5 to enter and infect host cells, coreceptor by which HIV infects cells Tropism: the way in which different viruses have evolved to preferentially target specific hosts *How might a cell biologist use the life cycle of a given retrovirus to study mechanisms responsible for protein targeting and sorting in eukaryotic cells? *Discuss which aspects of the study of retroviral life cycles directly contributed to the development of recombinant DNA technology. Using the reverse transcriptase in PCR to form new strands of DNA. *Suggest a procedure for how a genetically-modified retrovirus might be used as a gene-delivery vehicle in gene therapy.take out the DNA/RNA in the retrovirus that codes for any proteins that cause adverse effects. Then replace it with your gene of interest. And then you introduce the retrovirus into the organism. With one sentence, indicate the contributions to cell biology by each of the following individuals Robert Hooke- development of compound microscope, coined the term cell, observed corkAnton Van Leeuwenhoek- first to observe single celled organisms with a microscope “beasties”, saw fungi, protozoa, algae, bacteria, archaea but not virusesPeyton Rous-discovery of the role of viruses in cancer. Rous Sarcoma Virus Irving Langmuir- generated Langmuir trough, made device to make measurements Gortel and Grendel- first to propose membranes were composed of lipid bilayersDavson- Davson proposed a cell membrane model that depicted the phospholipid bilayer sandwiched between two layers of globular proteins. Danielli Singer- membrane consisted of lipid bilayer covered in globular proteins Nicolson Linus Pauling- identified what holds proteins together Review the general structural features and compositions of: T4 phage, tobacco mosaic virus, adenovirus, and the Rous Sarcoma Virus.tobacco mosaic virus- has capsid, about 6400 RNA basesadenovirus- double stranded DNA, no reverse transcriptase, capsid protein cover surface of virus, responsible for 10% childhood infections, 20 faced surfaceT4 phage- bacteriophage, double stranded DNA genome, Rous Sarcoma Virus: retrovirus/ oncovirus, *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? unit membrane: proteins are coating membrane on both sidesWhat are the major constituents of biological membranes of eukaryotic cells? constituents of membranes: composition reflects functional difference1. lipids2. proteins3. carbohydrates *Give the structure and name of a saturated fatty acid. Show the structure of the fatty acid when it is unsaturated. octanoic acid What are the constituents of a phospholipid?Fatty acid- can be saturated of unsaturatedChain of carbon atomsCharged carboxylic group Glycerol- 3 carbons and 3 OPhosphate groupCharged polar molecular like choline *Draw the structure and label the constituents of a phospholipid. Define each of the following terms Amphipathic Hydrophobic Hydrophilic One end is water soluble the other is lipid solubleHydrophilic (charged end)Hydrophobic (uncharged end) *Draw the structure of cholesterol and indicate why the molecule is amphipathic Only in eukaryotesRigid ring structure + single hydroxyl group (polar) + short hydrocarbon
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