CH 22 Flashcards
3 major cell types of prokaryotes
Rods (bacillus), sphere (coccus), spiral (spirilla or spirochetes)
Almost all prokaryotes have a
cell wall
Function of cell wall, what is it made of
- Lies outside the plasma membrane
- Protects and prevents cell lysis
- Bacteria’s cell wall is made of peptidoglycan (PG)
- Archaea’s cell wall is made with other structural polysaccharides
what do gram stains do??
Gram stains help determine the cell wall type.
- A positive gram stain is purple. Shows bacteria with thick peptidoglycan layer
- A negative gram stain is pink. thin PG layer PLUS outer lipid bilayer membrane (has 2 phospholipid bilayers), outer lipopolysaccharide (LPS) layer that is toxic and resists drugs & immune system
True of False: many prokaryotes have a capsule or slime layer
True
4 functions of capsule/slime layer
- sticky carbs and proteins secreted outside cell wall
- adheres (glues) cells together or to surface (throat, rock, etc)
- resists attack from immune system (divide and grow before being discovered)
- holds in moisture (self preservation)
Some proteins have a hairlike protein ______.
fimbriae. Helps cells stick to surfaces and each other. Help bacteria colonize.
Sex pilus (pili=plural)
pulls 2 bacteria cells together for DNA transfer (conjugation), forms mating bridge. NOT SEXUAL REPRODUCTION, can exchange beneficial traits
taxis meaning. what are the 3 types
movement directed toward or away from a positive or negative stimulus
chemotaxis, phototaxis, geotaxis (magneto taxis)
how do prokaryotes move?
rotating flagellum protein fibers, not homologous to eukaryote flagellas
what do spirochetes have?
internal flagella
slime gliding
less understood, slime ejected through pours
where is the DNA located?
nucleoid (organized region of DNA and proteins)
what type of ribosomes? microtubules yes or no?
free ribosomes. no mictrotubules
in-folded plasma membranes
folds in the membrane that increase membrane surface area, enhance cell’s efficiency. only some have it. this is for aerobic cellular respiration or for O2 producing photosynthesis. BACTERIA THAT HAVE THIS LOOK SIMILAR TO MITOCHONDRIA AND CHLOROPLASTS
How many chromosomes in prokaryotes? what type of DNA
one chromosome, circular DNA with binding proteins. no histones, archaeans have histones, which ties them closer to eukaryotes. genes are much closer together
many have plasmids.
plasmids are the tiny DNA circular rings with few genes IN ADDITION TO THE MAIN BACTERIAL DNA. they usually carrynextra beneficial traits. plasmids can replicate independently of the main bacterial DNA. add diversity. random number plasmids per daughter cell
Binary fission
simple, asexual reproduction, cell divides into two genetically identical cells EXCEPT FOR PLASMIDS. short generation time
some bacteria can form resting spores
during environmental stress, bacteria can transform into endo/resting spore, where they can remain dormant and survive harsh conditions. some are pathogens, very resilient
akinetes
resting spore for when pond dries up rehydrates cyanobacteria. specifically cyanobacteria
importance of DNA mutations
prokaryotes have a low rate of point mutations. however because they have such a rapid generation time and rate of cell division, there are a lot of mutations. so it offsets it.
one mutation can change
phenotypes. they only have 1 chromosome, genes are more directly correlated to phenotype. all mutations (except lethal ones) are passed on in clones (from binary fissions)
Griffith’s experiment
Recombination by transformation. used mice. living S cells, mouse dies. Living R cells, mouse lives. Heat killed S cells, mouse lives. Heat killed S cells + living R cells = mouse dead. dead S cells lyse, releasing DNA. R cells pick up DNA and incorporate into genome.
horizontal gene transfer
DNA fragments from donor cells are absorbed directly by recipient. Homologous DNA with new alleles exchanges with DNA in chromosomes (recombination). Donor’s DNA combines with recipient DNA.
Recombination by transduction
DNA is carried by bacteriophage virus (virus that only infects bacteria). Phages inject viral DNA into bacteria. Uses host/cell resources to make more phages.
Transduction mistake
a phage capsule will accidentally trap bacterial DNA instead of viral DNA (whoops!) new alleles inserted into recipient cell (recombination). cross over incorporates new DNA alleles into chromosome. RECOMBINANT CELL IS DIFFERENT FROM BOTH DONOR AND RECIPIENT CELL!