Biology
Review sheet 2nd Exam I.) ProkaryotesA. Characteristics of prokaryotes1. Shape of prokaryotes    – Spheres (Cocci)  – Spherical (Helices)  –  Rods (Bacilli)2.) The cell   – Very small   –  One circular chromosome located in a region called nucleoid  – Some species have a smaller ring of DNA called plasmid – confer antibiotic resistance  – Cell wall – protects the plasma membrane and helps resist it from rupturting – Flagella – allows for movement- Pili- proteins that helps cells adhere to a surface or facilitate conjuctionCapsule – slime layer made of polysaccharide that can surround the wall Plasmid- DNA molecule that carries accessory genes separate from those of a bacterial chromosome. **Antibiotic resistance in bacteria in relation to plasmids are drugs, which contain killer components for bacteria but the bacteria are able to penetrate and survive**3.) Gram stain – Stain in which tests to see if peptidoglycan is present – Eubacterial cell wall includes peptidoglycan – if positive (purple, thick cell wall and consist primarily of peptidoglycan- if negative (pink, cell wall has 2 layers, a thin peptidoglycan layer and thick outer membrane)Peptidoglycan – TYPE OF polymer in bacterial cell walls consisting of modified sugars cross linked by short polypeptides B. Bacterial growth and reproduction 1. Nature of bacterial growth – Counted by number (division) some less than 20 mn – Bacteria grows exponentially,  1 bacteria could be 2 million in a few hours – Divide by bacterial fission – cell mechanism used only by bacteria , involves replication of single bacterial chromosome and division of a parent cell into two genetically equivalent daughter cells Budding- cell develops a bulge or bud that enlarges and eventually separates from the mother cell Fragmentation – wall develops within the cell, which then separates into several new cells Conjuction – plasmids are transmitted to daughter cells and may be transferred to the cells of the same species or different species Transduction- virus carries bacterial gene from one bacterial cell to another (virus gets inside)Transformation- cell can absorb and integrate fragments of DNA from their environment (allows genetic transfer between prokaryotes even across species lines)
Archaebacteria Live in extreme environments (no peptidoglycan)Methanogens (anaerobiv strict, use H2 as a source of energy) Ex: MethanobacteriumHalophiles (salt lakes, use animal hides, spoil salted fish, make ATP by aerobiv pathway or photosynthesis) Ex: Halobacterium Thermaoacidophiles : hot water and highly acidic, use H2S as electron donor to make ATP. Ex: ThermoplasmaEubacteriaHave peptidoglycan in the cell wall Gram negative – Proteobacteria (enterobacteria – E.Coli, Salmonella)Vibrio- CholeraChlamydiasSpirochetesCyanobacteriaGram Positive actinomyceteslactic acid bacteriastreptococcistahyloccocciclostridiaPhotoautotrophs – use sunlight and CO2 during photosynthesis Ex: cyanobacteriaPhotoheterotrophs- sunlight, energy, and organic compounds as source of common Ex: RhodospirilumChemoautotrophs- use CO2 (not sunlight) obtain energy by stripping electrons from organic or inorganic substances Ex: nitrobacterChemoheterotrophs- most common, either parasites (draw carbon and energy from living hosts) or saprobes (feed on organic products, wastes or remains of other organisms , most bacteria fall under this category Ex: E.coli, lactobacillusVirusesCharacteristis of VirusesNon-living No cellular agents that infect particular species of nearly all organismsEach virus particle consist of : core of DNA or RNA protein coat tha sometimes in enclosed in a lipid envelopemany glycoprotein spikes project from these envelopescoats of complete viruses have sheaths, tail fibers and other accessory structures Virus Multiplication Cannot reproduce on its ownGenetic material must enter a host cell and direct the cellular machinery to synthesize the materials necessary to produce new virus particlesAttachment to a suitable host cell Penetration of itDNA replication and protein synthesisAssembly of new VIRAL particlesReleaseLytic infection: multiplication is rapid and new viral particles are released by lysis.  Ex: will attach to a genome and then as a result you will get sick Lysogenic infection: infection enters a latent period. The host cell is not killed at first and then the viral nucleic acid can undergo genetic recombination with a host cell chromosome, attaches to a genome and stays there forever.  Stress can cause this to be lethal