Topic 7- first life: prokaryotes Flashcards
prokaryotes have no ______________ unlike eukaryotes
membrane bound nucleus/ other organelles
Which domains are prokaryotes?
domain bacteria and domain archaea
The first unicellular organisms were ____( first life)
prokaryotes
What 3 things makes prokaryotes so adaptable/ successful ?
- small size (few needs)
- reproduce via binary fission (fast, don’t need to find a mate)
- short generation time (evolution can occur quickly, but may be inhibited by asexual reproduction)
prokaryotic cells have ____ DNA, and a nucleus that __(is/ isn’t) enclosed by a membrane
circular
is not
What does taxes mean? (singular = taxis)
give an example
movement away from or towards stimulus
eg. positive phototaxis is movement toward light
Plasmids are present in prokaryotes. Define plasmid
small rings of dna containing a few “extra” genes
prokaryotes have/ lack membrane enclosed organelles
some have ____ __ ____ ______
lack
infolding of cell membrane
despite reproducing asexually, prokaryotes have high genetic diversity. how?
- short generation time and high mutation rate compared to eukaryotes = increased diversity
how do bacteria exchange genetic info? (modify their genome)
genetic recombination via horizontal gene transfer
name and explain the 3 types of horizontal gene transfer
- transformation: ‘naked’ dna is picked up from dead bacteria in the environment (b/c when a cell dies, dna is released)
- transduction: dna transferred by virus (bacteriophage)
- conjugation: dna transferred between 2 bacteria
define autotrophs and their 2 varieties
autotroph: make their own energy from inorganic sources
- chemoautotroph: use energy obtained by oxidizing inorganic chemicals, and co2 ( doesn’t need sunlight)- many prokaryotes
- photoautotrophs: use light energy and co2 (primary producers that support food web) eg. cyanobacteria–> O2!
define heterotrophs and their 2 varieties
- don’t make their own energy! most bacteria must eat… enzymes digest organic molecules in environment absorbed through membrane
- photoheterotrophs: uses light energy; C source from organic molecules to help them process energy
- chemoautotrophs: use organic molecules for both energy and C source (eg animals, fungi, many prokaryotes, a few plants)
many prokaryotes are symbiotic. If inside the host organism it’s ____
endosymbiotic
define commensalism
A lives on/ with B, but neither harms nor benefits B
define amensalism
A harms B, but A does not gain anything from it
Studies of ___ structure revealed that there are actually __ very different lineages of prokaryotes
RNA
2
bacteria have _____ in their cell walls
peptidoglycan
archaea have more/ less variety in rna than bacteria
more
why don’t archaea respond to antibiotics?
antibiotics act on the peptidoglycan in the cell wall & cause the cell wall to break (inhibits eubacterial growth)
therefore antibiotics only work on bacteria, not archaea
most archaea live in ____ environments
extreme
archaea methanogens live in _______
they produce ___ as a waste product
oxygen-free habitats such as swamp substrates and cow guts
methane
archaea halophiles live in ____
very salty habitats
archaea thermophiles live in ____
many are
very hot environments
chemoautotrophs
cell wall in bacteria contains ____ which provides ___(list 3 things)
peptidoglycan
- cell shape
- protection
- prevents cell form exploding when placed in hypotonic solution (lower in solutes than cell content)
explain gram positive bacteria
they have peptidoglycan in cell wall in contact with external medium which traps purple stain
explain gram negative bacteria
have lipopolysaccharide layer outside of cell wall, and thus do not absorb stain readily
gram - species are often more ___ because the ____ layer can contain ___ and resist the action of ______
pathogenic
lipopolysaccharide
toxins
antibiotics
scientists hypothesize that mitochondria evolved from ______ __ ____ through _____
aerobic alpha proteobacteria
endosymbiosis
proteobacteria include ____mutualists called ____
describe the relationship
endosymbiotic
rhizobium which live in roots, and fix atmospheric nitrogen for the host to use in its metabolism
- the host plant then gives rhizobium carbohydrates
e.coli is an example of a ____
proteobacteria
it’s a harmless commensal in human intestine
______ and ____ are pathogenic bacteria
chlamydias and spirochetes
cyanobacteria are ____trophs and produced O2 in atmosphere billions of yrs ago
- ___ evolved form cyanobacteria
photoautotrophs
chloroplast
gram + pathogenic bacteria include
- clostridium botulinum (botox!)
- tuberculosis
- anthrax
list 4 similarities among both domains of prokaryotes (bacteria and archaea)
- no membrane bound organelles
- single, circular chromosome structure
- small size
- cell wall is present
list 4 differences among both domains of prokaryotes (bacteria and archaea)
- peptidoglycan in bacterial cell walls, not archaea
- plasma membrane is unbranched, Esther linkage in bacteria, and branched Esther linkage in archaea
- bacteria have linked RNA polymerase varieties, archaea have multiple
