chapter 27 Flashcards
what are prokaryotes?
single-celled organisms that make up domains bacteria and archaea. Adapted to diverse & extreme environments, they are the most abundant organism on earth
what are the 2 domains of prokaryotes?
bacteria & archaea
what is the cell wall?
maintain cell shape, cell protection, & prevents it from bursting in a hypotonic environment.
what is peptidoglycan?
a network of sugar polymers cross-linked by polypeptides. found in the cell wall
what is a gram stain?
classify bacteria
what does gram-positive mean?
simpler walls with a large amount of peptidoglycan
what does gram-negative mean?
less peptidoglycan & an outer membrane that can be toxic. more resistant to antibiotics
mutialism: +,+ commensalism: +,0
parasitism: +,-
what are the sticky layers of polysaccharides or protein surrounding the cell wall?
if it is dense, & well-defined it is called a capsule. if it is unorganized it is called a slime layer.
what do capsules and slime layers do?
enable adherence to substrate or other individuals, prevent dehydration, & protect the cell from the host’s immune system
what is fimbriae?
they stick to their substrate or other indiviuals in a colony
what is pili?
longer than fimbriae, allow prokaryotes to exchange DNA
what are endospores?
bacteria form these metabolically inactive pockets when water or nutrients are lacking. can withstand extreme conditions and remain viable for centuries
what is taxis?
the ability to move toward or away from a stimulus
what is chemotaxis?
movement toward or away from a chemical stimulus
what is flagella?
scattered about the surface or concentrated at one or both ends
describe internal organization & DNA
lack complex compartmentalization, some have specialized membranes that perform metabolic functions, less DNA than eukaryotes, circular chromosome, located in nucleoid region, have plasmid (smaller rings of DNA)
describe prokaryotic reproduction?
they are small, reproduce by binary fission, have short generation times and evolve quickly
what factors contribute to high levels of genetic diversity in prokaryote populations?
rapid reproduction, mutation, genetic recombination
describe rapid reproduction & mutation
cells produced by binary fission are identical, but differences arise through mutation. mutation rates are low, but can accumulate rapidly with short generation times & large populations. rapid production enables rapid adaptation by natural selection
what is transformation?
prokaryotic cell takes up & incorporate foreign DNA from the surrounding environment
what is trnasduction?
movement of genes between bacteria by bacteriophages
what is conjugation?
genetic material is transferred between prokaryotic cells. a donor cell attaches to a recipient by a pilus, pulls it closer and transfers DNA
how does conjugation occur in E. coli?
a pilus of the donor cell attaches to the recipient, the pilus retracts, pulling the cells together, DNA is transferred through a temporary structure called the “mating bridge”
what is the F factor?
the piece of DNA required for production of pili (F=fertility). Can exist either as a plasmid or a segment of DNA within the bacterial chromosome
How can prokaryotes be categorized in terms of obtaining energy?
Phototrophs: energy from light
Chemotrophs: energy from chemicals
Autotrophs: require CO2 compounds as carbon source
Heterotrophs: require organic nutrient to make other compounds
how do prokaryotes metabolism vary with respect to O2?
Obligate aerobes: require O2 for cellular respiration
Obligate anaerobes: poisoned by O2 & use fermentation or anaerobic respiration
Facultative anaerobes: can survive with ot without O2
