Bacterial and Archaeal cell Structures Flashcards
(47 cards)
1
Q
What kind of shapes can the cells take on?
A
- many, such as spheres, commas, spirals
- they can cluster, form rods, and fruiting bodies
- overall very diverse
2
Q
what is the cell membrane?
A
- the fluid mosaic model for plasma membrane applies to bacteria too
- bacteria use same ester linkage as eukaryotes
3
Q
permeability of membrane
A
- is amphiphathatic with hydrophobic & hydrophilic domains
- small uncahrged, polar molecules can cross (h20,urea,glycerol)
- hydrophobic molecules can
- large uncharged polar molecules and ions cannot diffuse across
4
Q
Isotonic solution
A
4
Q
Isotonic solution
A
equal concentration of solutes in cell and out of the cell, optimal for cell growth
5
Q
Hypertonic solution
A
- solute concentration is increased out the cell, the cell loses water, plasmolysis
6
Q
Hypotonic solution
A
- solute concentration is lower outside the cell, water then goes into the cell
- high osmotic pressure, potential lysis
7
Q
External features of a prokaryotic cell ?
A
- flagella, fimbriae, slime layer, etc.
8
Q
Features of the envelope on a prokaryotic cell?
A
- outermemebrane with LPS
- lipoprotein
- cell wall
9
Q
Internal features of a prokaryotic cell?
A
- the cytoplasm, cytoskeleton, nucleoid/chromosome, ribosomes, inclusions
10
Q
Gram positive bacteria
A
- bacterial envelope has a thick outer cell wall
11
Q
Gram-negative bacteria
A
- bacteria envelope does not have thick outer membrane
- cell wall anchored to the inside of the outer membrane
12
Q
What is peptidoglycan (murein)?
A
- what builds the cell wall as muramic acid and (NAG) polymerize into a chain
- peptide side chain on (NAM) can the link together with neighboring chains
13
Q
What links together the peptide groups in a gram-positive bacterium?
A
- peptides are linked together with (Gly)x5
- tight link, with low mobility
14
Q
How does a gram-negative cell wall differ from that of a gram-positive?
A
- the link between the peptides is more flexible
link is between a Diaminoacid (DAP) and D-Ala
15
Q
How is the cell wall of a gram-negative cell more complex that of a Gram-positive?
A
- the outer surface of the membrane has Lipopolysaccharides (LPS), which vary in shape and size and can function as another barrier, slowing down diffusion
- transport into the cell is harder: use porins: generalized receptor
16
Q
Lipopolysaccharides have four main sections, what are they?
A
lipid A, inner core, outer core, and O- anitgen
17
Q
What is the lipid A section of an LPS ?
A
- lipid A is the most conserved section of the LPS, as it’s in the bacterial envelope (unexposed)
- conserved in all species
- can have fatal immune responses to lipid A (endotoxin)
18
Q
What is the inner core section of the LPS?
A
- section after lipid A
- also highly conserved among all species
19
Q
What is the outer core section of the LPS?
A
- the section after the inner core
- less conserved among species
20
Q
What is the O-antigen of the LPS?
A
- the outer part of the LPS
- varies between species
- recognized by the immune system
- can be used to ID by “O-antigen” type
21
Q
What are porins?
A
- make pores in the outer membrane
- specific family of channel proteins
- gram-negative exclusive
22
Q
What are Acid-fast bacteria ?
A
- bacteria with a waxy layer that makes cells resistant to acid, soaps (no lipid bilayer)
- waxy layer slows down nutrient uptake and growth
- does not react with much, but do have proins
ex) Mycobacterium tuberculosis
23
Q
What are mycoplasmas?
A
- cells that lack a cell wall completely
(many antibiotics target cell walls) - many mycoplasmas use sterol extensively in their membranes from some structure
- live in or on host cells
- no need for a cell wall because of host homeostasis
24
What is an S-layer in bacteria?
- surface layer of protien,
25
What is an S-layer in bacteria?
- a surface layer of protein, primarily single monomers
- can provide shape or protein
- does impair diffusion
* Archea can also make S-layers
26
What are Capsules/ Slime layers ?
- when contents of the cell are spewed out
- usually polysaccharides, a few are amino acid polymers
- limit diffusion of harmful compounds, limit drying out
- avoid phagocytosis, can hide O-antigen from immune cells
27
What is the glycocalyx function?
- allows cells to adhere to surfaces and each other Biofilms
28
What are some the flagellar arrangements?
- Monotrichous
- Lophotrichopus (multiple)
- Peritrichous ( a lot)
- Axial filament (flagella inside of cell)
29
How does the flagella differ in gram-negative vs gram positive?
Falgella in gram-negative are more complex and have a basal body
in gram-positive, flagella are simpler as cell wall keeps it in place
30
What is a basal body in a flagellum?
- multi protein complex
- rings anchor it into the envelope of the cell
- basal body is built first, hollow flagella*
31
How would you explain the assembly of a flagella?
- basal body is built first --> hook --> Filament
- built from the bottom-up
- filaments self-assemble
32
What are flagellin?
- a subunit structures that self-assemble as they grow through the base
- these bits break off frequently and are antigenic
33
What is a bacterial pilus?
- kind of like a grappling hook, single monomer
- can be rapidly assembled and disassembled to change length
- functions include conjugation, attachment, twitching motility
34
What is a bacterial pilus?
- kind of like a grappling hook, single monomer
- can be rapidly assembled and disassembled to change length
- functions include conjugation, attachment, twitching motility
35
What structure in a bacterial cell organizes the DNA?
- the nucleoid
- DNA is not strictly separated from the rest of the cell
- transcription and translation occur together
- DNA just sits in the cell, the nucleoid
36
What structure within a cell organizes the rest of the cell?
- the cytoplasm
37
What do the specialized structures gas vesicles?
- made from protein
- common among aquatic photosynthetic microbes like cyanobacteria
- can tune buoyancy for optimum light
38
What are Thylakoids?
- extension of the cell membrane
| - enhance light-gathering abilities by increasing membrane surface area
39
What are carboxysomes?
- structure that houses Rubisco
- gases naturally diffuse, has proteins to get needed material
- seems to enhance the function of Rubisco
40
What are storage Granules?
- hold uniform chunks of useful material when in abundance for later use
- good long-term storage for carbon
41
What are magnetosomes?
- membrane-bound, iron-containing structures
- several chained together act as a compass needle
- help with up down movement in water column
42
What are the main differences between archaeal and bacterial envelopes?
- bacterial enveloped are bilayer
- archaea typically have monolayers, which provide more rigidity and structure at higher temperatures
- archaea membrane structure increases steric hindrance
43
True of false Archaea mainly have one form of envelope structure?
- false, many variety
44
How does the (1-3) linkage between the amino acids in archaea walls affect them?
-gives them the 1-3 linkage which, our lysozyme enzyme can only cut through 1,4
45
What are three ways in which archaea differ from bacteria?
- archaeal ribosomes are an intermediate between bacterial and ribosomes
- archaea use histones-like proteins in chromosomes management:
- archaeal flagella are superficially similar but powered by ATP hydrolysis
46
How do Enterosomes differ from carboxysomes?
- enterosomes don't have RuBisCO
