Prokaryotes Flashcards
1
Q
What are the domains of Prokaryotes?
A
Archaea. Bacteria.
2
Q
Describe the Coccus shape?
A
Round or roundish
3
Q
Describe the bacillus shape?
A
Rod
4
Q
Describe the Spirillum/Spirochete shape?
A
Curved from
5
Q
What is the Coccobacili shape?
A
Between coccus and a rod
6
Q
What is the cell structure of a prokayote?
A
Cell membrane. Nuceloid. No real internal structures. Flagellum
7
Q
What are the cell membranes in Prokaryotes?
A
Phospholipid bilayer (usually).
8
Q
What is the cell envelope?
A
The cell wall and the cell membrane
9
Q
What is the cell wall in a Prokaryote?
A
Peptidoglycan/muerin. Made up of alternating links o 2 amino sugars (NAG and NAM). Linked in long repeating chains with cross links.
10
Q
What is the difference in the cell wall of archaea?
A
N acetyltalosaminuronic acid. Different amino acids. All L amino acids in side chain.
11
Q
What can most bacteria be categorised into?
A
Gram-positive and Gram-negative
12
Q
What are the properties of Gram-positive?
A
Peptidoglycan. Membrane
13
Q
What are the properties of Gram-negative?
A
Peptidoglycan. Membrane. Outer (lipopolysaccharide). Periplasm
14
Q
What are the properties of cell envelopes in archaea?
A
- Phospholipid monolayer
- Single molecules
- Biphantyl, makes it much stronger
- Must have a layer protein
- Rigid wall of meurin like compound
15
Q
What are the ‘internal’ structures of prokaryotes?
A
Nucleoid. Ribosomes. Cytoskeleton. Intracellular granules. Spores.
16
Q
Describe the structure of the nucleoid.
A
- DNA, bound in the cell
- Single circular chromosome
- Plasmid, circle DNA, carries genes not essential
- Plasmids can be taken up and injected
- DNA coiled round proteins
- Plasmid supercoiled
17
Q
Describe the structure of ribosomes.
A
Lots and lots of ribosomes. Slightly different eukaryotic. 30S and 50S components
18
Q
Describe the structure of Cytoskeleton
A
- Formed by polymeric proteins
- Filamentous structures
- Maintains cell shape, motility and molecules trafficking
- MreB, ParM and FtsZ (protein)
19
Q
WHat does FtsZ do?
A
Important in cell fivision. Forms a ring mid cell and attracts proteins to that side.
20
Q
Describe the function granules.
A
- Storage of granules
- Polymeric reserves of nutrients
- Mostly glucose (glycogen)
- Magnetosomes
21
Q
What are magnetosomes?
A
Granules of magnetic material enclosed in a membrane. Acts like a compass
22
Q
Describe the function of spores.
A
Survival structures. Spores formed within the cell
- Endosperms
- Can survive harsh conditions
- Bacteria can shut down (hibernate)
- Can kill, autoclave at 120 degrees
23
Q
What are the ‘external’ structures of prokaryotes?
A
Glycolcalyx. Capsules. Pili and fimbriae. Flagella
24
Q
What is glycocalyx?
A
Loose network of fibrils. Slime layer (sticky). Glycoprotein. Helps adherence of bacteria to surfaces.
25
What are capsules?
Polysaccharide material. Thick gelatinout layer outside cell wall. Helps pathogenic bacteria to invade the host.
26
What is Pili and fimbriae?
- Organised structure
- Play a role in adherence
- Fimbriae = hair like, sticks to things
- Pili = attach bacteria together for conjugation
27
What is flagella?
- Used for locomotion
- Hollow tube composed of protein
- Flagella rotates and allows movement
- Different arrangements
28
How do prokaryotes reproduce?
Binary fission
29
Describe binary fission?
- Cell growth, B or G1 period
- Chromosome replication, C period
- Septum formation and cell division, D period
- Separates into two equal sized daughter cells
30
What protein is binary fission initiated by?
FtsZ
31
Describe the role of FtsZ in binary fission
- Acts as an organiser protein
- Focal point for everything else in cell division
- Forms a polymer ring around the equator where the cell will divide
- In presence of GTP acts as the point to get this process to happen
32
How does FtsZ know where midcell is?
- Controlled by complex protein system
- MinCDE system, series of proteins
- Makes sure FtsZ goes to the right place
- MinCDE system repeatedly builds up and is broken down in polar parts of the cell
- Components shuttle to the other end of the cell and build up and break down
- MinC prevents Z ring formation
- High conc. at the ends so more FtsZ in the centre
33
How is peptidoglycan made?
Bactoprenol takes building blocks across the cytoplasmic membrane. Transglycosylases catalyses insertion of the precursor in the growing point of the cell wall and catalyse glycosidic bond formation.
34
What is the carrier molecule in the production of the cell wall?
Bactoprenol
35
Where is the septum placed?
Located between the 2 newly replication chromosomes. Everything needs to be in the right position before septum is formed
36
How do bacterial chromosomes replicate?
Bidirectionally from a single origin
37
Where is the origin that chromosomes start to replicate?
Region where special DNA sequences are repeated.
38
Describe the process of chromosomal replication
- Starts at origin
- Initiation protein called DnaA (binding of multiple copies_
- Bending the DNA in a loop
- Replication proteins add to this complex forming two replisomes (replication forks)
- Termination of replication is when replisomes reach a special region = the terminus
39
What do interdivision times depend on?
Rich environment = fast. Poor environment = slow growth = long interdivision
40
Describe the time periods of the different stages in binary fission
B/G1 is variable. C phase and D phase are always the same. Cell cycles can overlap.
41
What is a rich medium?
Contains organic compounds. Want to grow as much as possible. Amino acids, vitamins, purines.
42
What is a minimal medium?
Want to see if a microorganism can grow on something specific. Only capable of growing with a compound. Has everything but a carbon source.
43
What is a broad medium?
Medium based on meat or yeast. Eg nutrient broth. Like rich medium.
44
What is a selective medium?
Only allow certain organisms to grow because it supresses out others. Promote growth of some bacteria and inhibits others.
45
What is a spectrophotometer?
Shines light of a known wavelength and determines the amount of light that gets through
46
What are some ways of measuring the amount of bacteria?
Dilutions or plate count
47
How do you do serial dilutions?
Take 1ml of culture 9ml broth. Dilute down by a factor of 10. Each dilution = less colonies. Count the one between 30 and 300, Multiply by dilution factor. Calibration curve and colonies
48
How do you work out the colonies from plate count?
If you know start number and growth.
| N = N0*2(^n)
49
How can a batch culture be modelled?
With a bacterial growth cruve
50
What is a batch culture?
Inoculated and left to grow
51
What is continuous culture?
Constantly adding and removing nutrients
52
What is the lag phase?
Taking time for bacteria to adjust to their environment
53
What is the log phase?
Rapid increase over time governed by growth conditions
54
What is the stationary phase?
Something starts to limit this process, growth stops
55
What is the death phase?
Can't survive so they die, become toxic, happens slowly as the dead bacteria release their contents. Others can feed off the contents and survive for slightly longer.
56
Give some examples of when bacteria can be beneficial and/or harmless.
Protection against colonisation by harmful bacteria. Production of antimicrobial compounds. Synthesis of vitamins. Stimulation of production of natural antibodies
57
When can bacteria turn from harmless to harmful?
Oppurtunistic. In immunocompromised patients. If you have a wound eg the result of surgery.
58
What is a pathogen?
Microorganisms that are able to cause disease in animals, plants or insects
59
What 2 mechanisms allow pathogens to get round our defenses?
Invasiveness and toxigenicity
60
What is virulence?
How rapidly bacteria cause infection
61
What is invasiveness?
Ability of a pathogen to invade the body, spread and establish an infection
62
What is colonisation?
Adherence and initial proliferation
63
What are bacterias routes of entry?
1. Inhalation (air)
2. Ingestion (food/water)
3. Contact
4. Bile
64
How does E.coli stick?
Uses pili and fimbriae.
- Type 1 fimbriae bind mannose on surface
- Ability to encode different fimbriae to associate with different host cells
- End of fimbriae
65
What are the 2 types of toxins bacteria can produce?
Exotoxins and endotoxins
66
How do exotoxins work?
Damage by producing toxic chemicals. Usually digestive enzymes that are secreted and destroy cellular structures.
67
What do does cytotoxin cause?
Diptheria toxin
68
How do cytotoxins work?
Damages cell affecting throat. Binds to epithelial cells. Prevents protein synthesis
69
What do neurotoxins cause?
Botulinum and Tetanus.
70
How does the botulinum toxin work?
Prevents release of acetylcholine in synapses. Nerves don't work anymore. Difficulty breathing and maintaining heartbeat leads to paralysis. Most acutely lethal toxin known.
71
How does the tetanus toxin work?
Tetanus (lockjaw). Puncture wound. Doesn't like aerobic conditions. Blocks release of inhibitory neurotransmitters at synaptic cleft so muscles fire and can't switch off = becomes rigid.
72
Describe the subunits A and B in exotoxins?
Subunit B = binds to receptor. Subunit A = can transfer directly into the cell or taken up through phagocytosis
73
Describe how an endotoxin works.
- Components of the cell envelope
- Gram negative
- Attached to bacterial cell
- Immune system rescognises and responds causing the symptoms
74
What is the bacterial pathogen vibrio cholera?
Causes cholera. In water. You lose water rapidly = dehydration. Produces a toxin
75
What is the bacterial pathogen yersinia pestis?
The plague. Rod shaped, gram negative. Vector borne. Haemorrhaging of lymph nodes. Buboes = bubonic plague. Inhalation = pneumonic plague
76
What are antibiotics?
Can kill or inhibit the growth of microorganisms but wont kill.
77
How do antibiotics work?
Interfere with bacteria specific biological processes eg cell wall synthesis, cell membrane structure or protein synthesis
78
What is the problem with antibiotics?
Bacteria can develop resistance that was previously killing them
79
How do bacteria gain resistance?
Chromosomal mutation or acquisition of a plasmid encoding resistance from a resistant bacteria. Can become resistant to multiple antibiotics
