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MCAT BIOLOGY (PRINCETON REVIEW)
CH. 5 MICROBIOLOGY WITH VERIFIED
CORRECT ANSWERS
obligate intracellular parasites viruses; virtually without activity outside of a living cell bacteriophage a virus that infects bacteria 6 Ways to Show Appreciation for Your Child's Teacher 0: / 0: capsid protein coat that surrounds a nucleic acid genome, provides the external morphology used to classify viruses (helical or polyhedral) tail fibers and base plate attach to the surface of the host sheath contracts using the energy of ATP to inject genome into host envelope in many animal viruses; membrane on the exterior of the virus is derived from the membrane of the host cell, contains phospholipids, proteins, and carbohydrates from the host membrane (acquired through budding) naked virus virus w/o envelope (most phages and plant viruses)
lytic cycle of phages
- Attachment/adsorption
- Penetration/eclipse hydrolase one of the first viral gene products; hydrolytic enzyme that degrades the entire host genome early gene group of genes that is expressed immediately after infection lysozyme destroys bacterial cell wall (EX: of late gene) lysogenic cycle phage genome incorporated into the bacterial genome prophage name for the phage genome after it is incorporated (inactive because phage-encoded repressor protein binds to specific DNA elements in phage promoters) lysogen name for the host after incorporation excision prophage becomes activated and removes itself from the host genome so it can enter the lytic cycle transduction virus integrates stolen host DNA along with its own genome in the new host genome replication of animal viruses
transmissible spongiform encephalopathies (TSA) --class of diseases in mammals that prions are responsible for --fatal holes develop in the brain bovine spongiform encephalopathy (BSE) also known as ma cow disease, transmitted from sheep to cows fatal familial insomnia (FFI) prion disease caused by autosomal dominant condition inherited on chromosome 20 Creutzfeldt Jakob Disease (CJD) another inherited prion disease; all have long incubation period viroids --short piece of single-stranded RNA with extensive self complementarity --do not code for proteins or have capsids --some are catalytic ribozymes or produce siRNAs when replicated --most diseases in plants Hepatitis D --the only human disease linked to viroids --usually coinfection w/ hepatitis B Cell Theory --Robert Hooke
- All living organisms are composed of one or more cells and their products
- Cells are the monomer for any organism
- New cells arise from pre-existing, living cells Domains Bacteria, Archea, Eukarya
polyribosome many ribosomes translating a single piece of RNA form this structure plasmids --a circular piece of ds DNA much smaller than the genome --extrachromosomal genetic elements --autonomous replication --may encode advantageous gene products --can orchestrate conjugation bacterial shape round, rod-shaped, spiral-shaped peptidoglycan --makes up the bacterial cell wall --cross linked chains of sugars and amino acids (D-alanine) protoplast osmotically fragile structure (cell wall) when lysozyme destroys peptidoglycan gram staining
- = light pink gram-positive thick peptidoglycan layer outside the cell membrane
peritrichous have multiple flagella structure of flagellum filament, hook, basal structure basal structure contains a number of rings that anchor the flagellum to the inner and outer membrane and serve to rotate the rod and the rest of the attached flagellum chemotaxis bacterial motion can be directed towards attractants or away from toxins chemoreceptors on the cell surface that bind attractants or repellents and transmit a signal that influences the direction of flagellar rotation (response to a change in conc.) pili long projections on the bacterial surface involved in attaching to different surfaces sex pilus special pilus attaching F+ (male) and F- (female) bacteria and facilitates the formation of conjugation bridges fimbriae smaller structures that are not involved in locomotion or conjugation but are involved in adhering to surfaces mesophiles moderate temp. lovers thermophiles heat lovers psychrophiles cold lovers
autotrophs utilize CO2 as their carbon source heterotrophs rely on organic nutrients created by other organisms chemotrophs get their energy from chemicals phototrophs get their energy from light chemoautotrophs Build organic macromolecules from CO2 using the energy of chemicals. Obtain energy by oxidizing inorganic molecules like H2S chemoheterotrophs Require organic molecules such as glucose made by other organisms as their carbon source and for energy photoautotrophs Use only CO2 as a carbon source and obtain their energy from the sun photoheterotrophs Get energy from the sun but require organic molecule made by another organism as their carbon source plating process of putting bacteria on such a plate minimal medium contains nothing but glucose (but agar) bacterial lawn the dense growth of bacteria in petri dishes plaque a clear area in the lawn doubling time the amount of time for a pop. of bacteria to double its time auxotroph
carrying capacity the max pop. at the stationary phase endospores --tough, thick, external shells comprised on peptidoglycan --some gram - bacteria form this when conditions are unfavorable --can only form one spore per cell germination metabolic reactivation of endospore transduction the transfer of genomic DNA from one bacterium to another by a lysogenic phage transformation if pure DNA is added to a bacterial culture, the bacteria internalize the DNA in certain conditions and gain any genetic info in the DNA F (fertility) factor an extrachromosomal element that is key to bacterial conjugation, single circular DNA molecule F+ bacteria that are male and have the F factor F- bacteria that are female and receive the F factor from male cells to become male conjugation bridge male produces sex pili and the pilli contact the female cell, F factor is replicated and transferred unidirectional Hfr (high frequency of recombination) cell F factor integrated into genome
Domain Archaea live in more extreme environments, walls lack peptidoglycan, genetically share many traits with eukaryotes parasite can be obligate or facultative
