Bio Ch 20 Flashcards
Virus
associated with a number of plant, animal, and human diseases; biological enigma
Capsid
all viruses have; composed of protein subunits and an inner core of nucleic acid (either DNA or RNA, but not both)
Obligate intracellular parasites
viruses; can’t reproduce outside a living cell
Bacteriophages (phages)
viruses that parasitize bacteria
Lytic Cycle
5 stages: attachment, penetration, biosynthesis, maturation, & release
Lysogenic Cycle
infecting phage does not immediately proliferate, but may do so sometime in the future; in the meantime, the phage is latent (not actively replicating)
Prophage
while latent, the viral DNA is called this
Lysogenic Cells
prophage is replicated along with the host DNA and all subsequent cells (called this) carry a copy of the prophage genome
Retroviruses
animal viruses with an RNA genome that is converted into DNA within the host cell by a special enzyme called reverse transcriptase
Reverse Transcriptase
special enzyme that converts an RNA genome into DNA within a host cell
Emerging Viruses
new or previously uncommon illnesses caused by viruses that are able to infect large numbers of humans; AIDS, West Nile encephalitis, hantavirus pulmonary syndrome (HPS), severe acute respiratory syndrome (SARS), Ebola hemorrhagic fever, and avian influenza (bird flu)
Viroids
naked strands of RNA (not covered by a capsid); causes crop diseases (potatoes, coconuts, citrus)
Prions
proteinaceous infectious particles; cause a number of fatal brain diseases known as transmissible spongiform encephalopathies (TSE’s); proteins that normally exist in an animal, but have a different conformation/structure; cause infection by interacting with a normal protein and altering its structure
Neurogenerative Diseases
TSE’s; those that destroy nerve tissue in the brain; ex = mad cow disease
Prokaryotes
bacteria & archaea; fully functioning, living, single-celled organisms
Flagella
some prokaryotes move by means of this; bacterial type has a filament composed of strands of the protein flagellin wound in a helix
Fimbriae
short bristlelike fibers extending from the surface of many prokaryotes
Nucleoid
dense area in a prokaryote where a single chromosome consisting of a strand of circular DNA is found
Plasmids
many prokaryotes have accessory rings of DNA called this; can be extracted and used to carry foreign DNA into host bacteria during genetic engineering processes
Binary Fission
prokaryotes reproduce asexually by means of this
Conjugation
two bacteria temporarily linked together, often by means of a conjugation pilus; while linked, the donor cell passes DNA to a recipient cell
Transformation
occurs when a cell picks up free pieces of DNA from its surrounding medium; this DNA has been secreted by live prokaryotes or released by dead ones
Transduction
bacteriophages carry portions of DNA from one bacterial cell to another
Bacteria
more common type of prokaryote
Peptidoglycan
part of the cell wall of bacteria; = complex of polysaccharides linked by amino acids
Gram-positive bacteria
single plasma membrane; thick peptidoglycan layer, stains dark purple
Gram-negative bacteria
stains lighter purple or lacks purple color completely; peptidoglycan layer is sandwiched between 2 plasma membranes; this extra, outer membrane reduces the amount of Gram stain that binds to the peptidoglycan, so iodine-dye complex is washed away; 2nd dye (safranin) needed to stain bacteria pink so that it can be seen under a microscope
Obligate Anaerobes
some bacteria are this; unable to grow in the presence of free oxygen
Facultative Anaerobes
some bacteria are this; able to grow in either the presence or the absence of gaseous oxygen
Photoautotrophs
photosynthetic; use solar energy to reduce CO2 to organic compounds
Chemoautotrophs
carry out chemosynthesis; oxidize inorganic compounds such as hydrogen gas, hydrogen sulfide, and ammonia to obtain the necessary energy to reduce CO2 to an organic compound
Chemoheterotrophs
take in organic nutrients
Saphrotrophs
aerobic bacteria that decompose almost any large organic molecule into smaller ones that can be absorbed; AKA decomposers
Symbiotic relationships
2 different species live together in an intimate way
Mutualism
both species benefit from their association
Commensalism
Only one species benefits while the other is unaffected
Parasitism
one species benefits while harming the other
Pathogens
parasitic bacteria that cause diseases
Endospores
some of the deadliest pathogens form these when faced with unfavorable environmental conditions
Toxins
in almost all cases, the growth of microbes themselves does not cause disease; the poisonous substances they release, called this, are the pathological portion
Cyanobacteria
Gram-negative bacteria with a number of unusual traits; photosynthetic
Lichens
cyanobacteria in association with fungi form these that can grow on rocks
Archaea
at one time thought to be unique group of bacteria; in 1977, Woese and Fox discovered that the rRNA of archaea has a different sequence of bases than the rRNA of bacteria
Methanogens
Methane makers; obligate anaerobes found in environments such as swamps, marshes, and the intestinal tracts of animals; chemoautotrophs; use H2 to reduce CO2 to methane (biogas)
Halophiles
archaea that require high salt concentrations (usually 12 - 15%); use chloride pumps that use halorhodopsin to pump chloride to the inside of the cell to prevent water loss; aerobic chemoheterotrophs
Thermoacidophiles
isolated from extremely hot, acidic environments, such as hot springs, geysers, submarine thermal vents, and around volcanoes; chemoautotrophic anaerobes; use hydrogen as electron donor and sulfur (or sulfur compounds) as terminal electron acceptors for their ETC’s; H2S and protons (H+) are common products
