Lecture 19- Prokaryotes Flashcards
Prokaryotes
Single celled organisms that make up domains Bacteria and Archaea; adapted to diverse and extreme environments and are the make abundant organisms on Earth
prokaryote shapes
cocci (spheres), bacilli (rods), spirals
function of prokaryotic cell wall
Maintains shape, protects the cell, prevents bursting in hypotonic environment
bacterial cell wall
contain peptidoglycan, a network of sugar polymers cross linked by polypeptides
archaea cell walls
contain a variety of polysaccharides and proteins, but lack peptidoglycan
gram positive bacteria
Simpler walls with large amount of peptidoglycan
gram negative bacteria
Less peptidoglycan, more complex with an outer membrane that contains lipopolysaccharides, stains pink
Capsule
Dense and well defined sticky layer of polysaccharide or protein surrounding the cell wall; slime wall if not well organized; sticky layer of polysaccharides or proteins
capsule functions
enable adherence to substrate or others, prevent dehydration, protest cell from host’s immune system
Fimbriae
hairlike appendages to stick to their substrate or others;
Pili
sex pili; longer than fimbriae and put cells together enabling exchange of DNA
endospores
a response to rapid environmental changes; metabolically inactive; cell copies chromosome and surrounds with multilayered structure; EXTREME CONDITIONS
Taxis
the ability to move towards or away from a stimulus; flagella commonly used
flagella
operate on harnessing a chemical gradient to power movement; kinetic;
internal organization of prokaryotic cells
lack complex compartmentalization, some have specialized membranes that perform metabolic functions- infoldings of the cell membrane; aerobic vs. photosynthetic
prokaryotic genetic material
one circular chromosome, contained in nucleoid (no membrane); some contain plasmid
plasmid
smaller rings of independently replicating DNA; carry addition genes that can be beneficial (antibody resistance), easy to manipulate
high levels of prokaryotic genetic diversity due to
rapid reproduction, mutation, genetic recombination
prokaryotic rapid reproduction
binary fission, divide every 1-3 hours; (small, binary fission, short generation times)
prokaryotic mutation
mutation rates low, but accumulate with short generation times and large populations; rapid adaptation
prokaryotic genetic recombination
transformation, conjugation, transduction; horizontal gene transfer (vertical is hereditary)
transformation
incorporate foreign DNA taken up by their surroundings, bacteria must be competent (permeable by chemical or heat shock)
transduction
phages (bacteriophages) carry prokaryotic genes from one host cell to another; unintended result of phage replicative cycle
conjugation
DNA is transferred between two prokaryotic cells, PILUS of donor attaches to recipient, cells pulled together, DNA transferred through mating bridge
F factor
piece of DNA required for the production of pili, exists as plasmid or segment of DNA in bacterial chromosome (fertility)
F plasmids
cell containing F plasmid acts as DNA donor; encodes genes for sexual pili and activate DNA synthesis, F+ can convert F- to F+ if full plasmid transferred, recombinant is only part
conjugation and chromosome
Hfr cells function as donors during conjugation, homologous segments recombine with segments of F- chromosome, new DNA incorporated need to be genetically similar!
metabolism
the totality of an organism’s chemical reactions, emergent property
metabolic pathways
begin with specific substrate or reactant and end with a product, digestion
catabolic pathways
release energy by breaking down complex molecules into simpler compounds (cellular respiration) CAT
prokaryotic metabolism
energy and carbon sources combined to give 4 groups
anabolic pathways
consume energy to build complex molecules from simpler ones (photosynthesis) WEIGHT LIFTING
anabolic prokaryotic pathways
photoautotroph, chemoautotroph
catabolic prokaryotic pathways
photoheterotrophh, chemoheterotroph
chemoautotrophs
use inorganic molecules to synthesize larger molecules (chemosynthesis), feed on chemicals that are good electron donors, most are extremophiles (living in extreme envcironments)
photoautotrophs
trap light energy and convert it to chemical energy, chloroplasts evolve form them (cynobacteria),may be oxygenic or anoxygenic
chemoheterotrophs
obtain carbon from other living organisms, break down bonds in complex molecules and harvest energy (cellular respiration), mitochondria evolved (alpha protobacterium)
obligate aerobes
require oxygen for cellular respiration
obligate anaerobes
poisoned by oxygen and live by fermentation or use other substances
facultative anaerobes
can use oxygen if presents or carry out fermentation or anaerobic respiration if not
photoheterotrophs
can’t use carbon dioxide so they break down larger organic molecules; capture light energy to convert to chemical energy
