prokaryotic cell structure Flashcards
1
Q
common features in prokaryotes and eukaryotes
A
- plasma membrane
- DNA
- cell wall (plant, fungal, almost all bacteria)
2
Q
most common bacterial cell shapes
A
- coccus (circle)
- coccobacillus (rod)
- vibrio (comma)
- bacillus (long)
- spirillium (helical)
- spirochete (long and helical)
3
Q
dividing bacteria
A
- can stay together for a period of time
- in pairs (diplococcus, break off after next division)
- in a chain (streptococci, associated for a longer time, more divisions occur)
4
Q
tetrad
A
- alternate orientation of plane of division so 4 bacteria stay together
- break up after 4
e.g. micrococcus
5
Q
cyanobacteria
A
- divide alternately to create single layer mats
- can float in water and photosynthesise
e.g. Merismopedia spp.
6
Q
sarcinae
A
- alternate planes of division to form clumps of 8
7
Q
ununiform division
A
- divide in random directions and stay together until clump gets too big, so break off and start dividing
e.g. S. aureus
8
Q
structure of a prokaryote
A
- cell membrane (+cell wall)
- cytoplasm with inclusions
- external structures
(capsules, flagella, pili)
9
Q
cell wall
A
- outside cell membrane in most
- some lack cell wall e.g. mycoplasmus
- peptidoglycan
- maintains shape of cell (no cytoskeleton)
- prevents cell from osmosis by stopping too much water diffusing in
10
Q
peptidoglycan
A
- alternating sugars to create strands
- N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
- crosslinked with tetrapeptide chains to create strong layers
11
Q
teichoic acid
A
- in cell wall of gram-positive bacteria
- glycerol, phosphates, ribitol (sugar alcohol)
- projects on/through peptidoglycan layer
- involved in movement of ions in/out cell
- bacteriophages can attach on
12
Q
outer membrane
A
- gram-negative bacteria only
- outside peptidoglycan layer
- porin proteins form channels through outer membrane for transport
- surface antigens and receptors for cell recongition
13
Q
periplasmic space
A
- gap between peptidoglycan layer and outer membrane in gram-negative bacteria
- contains digestive enzymes
14
Q
ribosomes
A
- all free in cytoplasm
- polyribosomes = chains of ribosomes
- 70s (80s in eukaryotes)
- antibiotics including streptomyocin and erythromyocin bind specifically to 70s ribosome, disrupting bacterial protein synthesis but not eukaryotic
15
Q
pili
A
- short hollow projections
- conjugation- gene transfer
- attachment to surfaces (host invasion)
16
Q
inclusions
A
- glycogen or polyphosphate storage granules (energy store)
- gas or lipid vesicles (storing energy or regulating buoyancy)
17
Q
flagellum
A
- for movement
- helically coiled
- thinner than eukaryotic flagella, ~20nm diameter
18
Q
capsule/slime layer
A
- covers antigens on cell surface so can help evade host immune system
19
Q
cell membrane
A
- separates cytoplasm from exterior
- phospholipid bilayer, proteins including transporters
20
Q
nucleoid
A
- nuclear region
- DNA, usually one circular chromosome
e.g. vibrio cholerae has one large one small chromosome - smaller circular plasmids holding extrachromosomal non-essential DNA
21
Q
storage granules in biotechnology
A
e.g. PHB granules, biodegradable plastic
parasporal BT crystal, insecticide (very selective)
suflur globules, carboxysomes
22
Q
endospores
A
- resistant resting structure
e.g. in Bacillus and Clostridium spp. - allows bacteria to survive inhospitable conditions
- protected against heat, UV, desiccation by spore coat
- one spore per bacterium triggered when nutrients start to die out
- mother cell deteriorates
- when conditions improve, spore germinates
23
Q
monotrichous (flagella)
A
single polar flagellum
24
Q
lophotrichous (flagella)
A
multiple polar flagella
25
amphitrichous (flagella)
one flagella at each end
26
peritrichous (flagella)
flagella all over surface
27
atrichous (flagella)
no flagella
