Topic 4 - Prokaryotic Cell Morphology Flashcards
(104 cards)
0
Q
Two componenets to peptidoglycan structure
A
- Two alternating sugars (N-acetylglucosamine (nag) and N-acetylmuramic acid
- Alternating D and L amino acids
1
Q
Has a meshlike polymer of identical subunits forming long strands
A
Peptidoglycan structure
2
Q
Shape that peptidoglycan has
A
Helical shape
3
Q
Peptidoglycan chains are crosslinked by what?
A
Covelent bonds between the tetrapeptides for strength
4
Q
Crosslinks are directly between amino acids in the tetrapeptide
A
Gram negative bacteria
5
Q
There is often an interbridge of additional amino acids between tetrapeptides
A
Gram positive bacteria
6
Q
Peptidyoglycan is only found where?
A
Bacteria
7
Q
What happens when peptidoglycan chains are crosslinked by peptides for strength
A
- Interbridges may form
- Peptidoglycan sacs - interconnected networks
- Various structures occur
8
Q
Gram positive cells walls are primarily composed of what?
A
90% of peptidoglycan
9
Q
What is the second component to cell walls in gram positive cell walls
A
Teichoic acids (negative charged)
10
Q
What is the importance of teichoic acids?
A
- Help maintain cell envelop
- May bind to host cells
- May store PO4; may attract cations
11
Q
Some gram positive bacteria have layers of what on where?
A
Proteins on surface peptidoglycan
12
Q
Last component to gram positive cell walls that attaches wall to membrane
A
Lipteichoic
13
Q
Lies between plasma membrane and cell wall and is smaller than that of gram-negative bacteria
A
Periplasmic space of gram positive bacteria
14
Q
The periplasmic space of Gram + bacterias has very few what?
A
Proteins
15
Q
Enzymes secreted by gram positive bacteria are called _____
A
Exoenzymes
16
Q
Aid in degradation of large nutrients
A
Exoenzymes
17
Q
Four IMPORTANT characteristics of gram negative cell walls
A
- More complex than Gram positive
- Consist of a thin layer of peptidoglycan surrounded by an outer membrane
- Outer membrane composed of phospholipids, lipoproteins, and lipopolysaccharide
- No teichoic acids
18
Q
Peptidoglycan is ______ of cell wall height and in the _____
A
- 5-10%
- Periplasmic space
19
Q
How is the periplasmic space different than that of gram positive cells?
A
- May constitute 20-4-% of cell volume
- Many enzymes present in periplasm
20
Q
The enzymes that is in the periplasmic space in gram negative cell walls
A
Hydrolytic enzymes
Transport proteins
Others
21
Q
In the gram negative cell walls, what is the structure and where do the different components attach?
A
- Outer membrane lies outside the thin peptidoglycan layer
- Braun’s lipoproteins connect outer membrane to peptidoglycan
- Other adgesion sites reported
22
Q
What are the three components to Lipopolysaccharide (LPS)
A
- Lipid A (endotoxin)
- Core polysaccharide
- O side chain (O antigen)
23
Q
Lipid A is embedded where in the LPS
A
Outer membrane
24
Where do the core polysaccharides and O side chains exist on the LPS?
Out from the cell
25
Six reasons why LPS is important
1. Contributes to negative charge on cell surface
2. Helps stabilize outer membrane structure
3. May contribute to attachment to surfaces and biofilm formation
4. Creates a permeability barrier
5. Protection from host defenses (O antigen)
6. Can act as an endotoxin (lipid A)
26
What is special about the gram negative outer membrane permability?
- It is more permeable than plasma membrane due to presence of porin proteins and transporter proteins
27
What do porin proteins do?
Form channels to let small molecules (600-700 daltons) pass
28
Why does the gram stain reaction happen?
Due to nature of cell wall
29
What happens in the reaction of gram stains?
- Shrinkage of the pores of peptidoglycan layer of gram positive cells
- Constriction prevents loss of crystal violet during decolorization step
- Thinner peptidoglycan layer and larger pores of gram negative bacteria does not prevent loss of crystal violet
30
Structures exterior to the cecll wall
1. Glycocalyx (Capsule and slime layer)
| 2. S layer
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Polysaccharide rich (glucose or modified glucose subunits) material exterior to cell wall; sometimes has protein component
Glycocalyx
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Dense; tightly attached; regular arrangement of polysaccharides; visible to light microscope
Capsule
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Diffuse; loosely attached; irregular arrangement of polysaccharides
Slime layer
34
Functions of the slime layer
Attachment to solid surfaces, anti-dessicant, reserve source of energy, anti-phagocytic for some pathogens, prevents virus attachment
35
What does the slim layer aid in?
Mobility
36
Regularly structured layers of protein or glycoprotein that self-assemble
S layer
37
Where does the S layer go in gram positive and negative bacterias
1. Gram negative = adheres to the outer membrane
| 2. Gram positive = Associated with the peptidoglycan surface
38
S layer functions
1. Protect from ion and pH fluctuations, osmotic stress, enzymes, and predation
2. Maintains shape and rigidity
3. Promotes adhesion to surfaces
4. Protects from host defenses
5. Potential use in nanotechnology
39
What happens to the S layer in nanotechnology?
S layer spontaneously associates
40
How do prokaryotes differ from eukaryotes?
- Most prokaryotes are smaller than eukaryotes
- Most lack an internal membrane system
- Prokaryotes do not have an internal phospholipid bilayer membranes
41
Two taxa prokaryotes are divided into
1. Bacteria
| 2. Archaea
42
The sizes of prokaryotic cells
- Most cultured rod shaped bacteria are between .5 and 4.0 um wide and < 15 um long
- Most spherical about 1 um diameter or less
- Large prokaryotes are > 500 um
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Example of a very large prokaryote
Epulopiscium fishelsoni
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Size range for eukaryotic cells
10 to >200 um in diameter (but some larger)
45
Cell shape
Morphology
46
Major cell morphologies
Coccus - spherical or ovoid
Bacillus (Rod; pl. Baccili) - cylindrical shape
Spirillum - spiral shape
47
Five different kinds of cocci
1. Diplococci - pairs
2. Streptococci - chains
3. Staphylococci - grape like chains
4. Tetrads - 4 cocci in a square
5. Sarcinae - cubic configuration of 8 cocci all perpendicular to each other
48
Different kinds of Bacilli
1. Diplobacilli - 2 bacilli
2. Streptobacilli - chains of bacilli
3. Pallisade - several parallel cells along long axis
49
Five different shapes of bacilli
1. Bacilli - rods
2. Coccobacilli - very short rods
3. Vibrios - resemble rods, comma shaped
4. Spirilla - rigid helices
5. Spirochetes - flixible helices
50
Network of long multinucleate filamentous cells
Mycelium
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Organisms that are variable in shape
Pleomorphic
52
Four characteristics commenting on the shape and arrangement of archaea
1. Pleomorphic
2. Branched
3. Flat
4. Square
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Advantages to being small
- Small cells have more surface area relative to cell volume than large cells
- Allows for greater nutrient exchange per unit cell volume
- Thus, small cells tend to grow faster than larger cells
54
Lower limits of cell size
1. Cellular organisms less than .15 um in diameter are unlikely
2. Open oceans tend to contain small cells (.2-.4 um in diameter)
55
Prokaryotic Cell Structure
1. Structures exterior to the cell wall
2. Cell wall
3. Cell membranes
4. Structures within cell membrane
56
What is the cell envelope?
1. Structures exterior to the cell wall
2. Cell wall
3. Cell membranes
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Three characteristics to the domain Bacteria cell envelope
1. Cell membrane
2. Cell wall
3. Layers outside the cell wall
58
Prokaryote cell membrane characteristics
1. Absolute requirements for all living organisms
2. Some prokaryotes also have internal membrane systems (but these are different from the internal membrane systems in eukaryotes)
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Cell membrane functions for all domains
1. Maintains cell's integrity - vital barrier that separates cytoplasm from environment (if not cell membrane, no cell)
2. Regulates transport - highly selective permeable barrier
3. Energy metabolism in prokaryotes (not eukaryotes)
4. Protein attachment
5. Receptors for detection of an response to chemicals in surroundings
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What is the Fluid Mosaic Membrane structure for all domains?
1. Membrane somewhat fluid, somewhat solid
| 2. Lipid bilayers with floating proteins
61
Describe the lipid bilayers with floating proteins
- Amphipathic lipids with polar ends and nonpolar tails
| - Membrane proteins
62
Composition of Domain Bacteria cell membrane
1. General structure - phospholipid bilayer plus proteins (6-8 nm wide); no sterols but +/- hopanoids or other molecules
2. Fatty acids point inward to form hydrophobic environment; hydrophilic portions remain exposed to external environment or the cytoplasm
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Loosely connected to membrane on cytoplasmic side
| - Easily removed
Peripheral membrane proteins
64
- Amphipathic (embedded within membrane and project outward or inward)
- Carry out important functions
3. May exist as microdomains
Integral membrane proteins
65
Completely crosses membrane from one side to the other
Transmembrane proteins
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How does the outer surface of cytoplasmic membranes interact with proteins?
Interact with a variety of proteins that bind substrates or process large molecules for transport
67
How does the inner surface of cytoplasmic membranes interact with proteins?
involved in energy yielding reactions and other important cellular functions
68
What are the membrane strengthening agents?
- Sterols
| - Hopanoids
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Describe sterols and where they are found
- Rigid, planar lipids found in eukaryotic membranes; strengthen and stabilize membranes
- Only found in a very few prokaryotes
70
- Structurally similar to sterols
| - Present in membranes of many Bacteria
Hopanoids
71
What does the saturation levels of membrane lipids reflect?
Environmental conditions such as temperature
72
Bacterial membranes lack what important structure?
Sterols, but they contain hopanoids which are sterol like structures
73
What do hopanoids do in bacterial membranes?
- Stabilize membrane
| - Found in petroleum
74
What do hopanoids do for bacterial membranes?
- Stabilize membrane
| - Found in petroleum
75
Liquid crystal, some properties like liquid, some like solid; needs to be at right fluidity which is temperature dependent
Cell membranes
76
A membrane that is too cold
Solidification (gelling)
77
A cell membrane that is too hot
Thermal lysis (cell death)
78
What do you have to do to maintain correct membrane fluidity?
1. Adjust fatty acid composition of phospholipids
- Cold - need more unsaturated fatty acids to minimize van der waals forces
- Hot - more saturated fatty acids to maximize van der waals forces
2. Adjust ratio of sterols, hopanoids or other lipids to phospholipids, to maximize or minimize van der waals forces
79
Transport which does not require ATP or other cellular energy to be used by the cell (but energy of molecules are involved)
Passive transport
80
Transport which requires the cell to expend its own energy in the form of ATP (or other cellular respiration)
Active transport
81
Transport which does not require a transport protein
Simple transport
82
Transport which requires a transport protein
Facilitated transport
83
The movement of a molecule due to its inherent kinetic energy from a region where it is in higher concentration to a region where it is lower concentration (passive transport)
Diffusion
84
The diffusion of water across a membrane (passive)
Osmosis
85
How a molecule gets across a phospholipid bilayer/protein membrane depends on several factors
1. The charge on the molecule - ionic, polar, non polar
2. The size of the molecule
3. The shape of the molecule
86
To pass across a phospholipid bilayer/protein membrane a molecule can go two ways
1. Between the phospholipids (simple transport) - must be non polar or a very small polar molecule
2. Through a transport protein (facilitated transport) - all ions and nearly all polar molecules
87
Diffusion between the phospholipids (passive and no transport proteins)
- Nonpolar molecules and water
Simple diffusion
88
Diffusion through a transport protein
| - Passive
Facilitated diffusion
89
Where is facilitated diffusion common?
- Eukaryotes; less common in prokaryotes; in direction of concentration gradient
- For ions and polar molecules
90
Any transport which requires the cell to expend its own energy; in prokaryotes, active transport is always facilitated and is in the direction against the concentration gradient
Active transport
91
Where does active transport take place?
- Can be ions, polar molecules and sometimes bigger non polar molecules
- No endocytosis.exocytosis in prokaryotes
92
Ligand binds specific protein receptors on cell surface
- Show saturation effect
- Highly specific
Receptor mediated transport systems
93
Simultaneous transport and chemical modification of transported substance
Group translocation
94
Best known translocation system for group translocation
Sugar phosphotransferase system (PTS)
95
Characteristics of domain Bacteria cell walls
1. Cell walls are exterior to cell membrane, rigid and mostly structural polysaccharides and peptides or protein
2. For unicellular and colonial prokaryotes, the primary function of the cell wall is to prevent osmotic lysis
96
Pressure from water entering cell causes a rupture of the cell membrane and death of the cell
Osmotic lysis
97
- Solute concentration outside the cell is less than inside the cell, and water concentration is higher
- Water moves into cell and cell swells
- Cell wall protects from lysis
Hypotonic environments
98
- Solute concentration outside the cell is greater than inside, water concentration lower
- Water leaves the cell
- Plasmolysis occurs
Hypertonic environments
99
Evidence of protective nature of the cell wall
1. Lysozymes breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid in cell wall
2. Penicillin inhibits peptidoglycan synthesis
* If cells are treated with either of the above they will lyse if they are in a hypotonic solution
100
- Does not produce a cell wall
- Plasma membrane stronger (w/sterols) more resistant to osmotic pressure
- Hyper regulates internal solute concentration to stay just slightly hypertonic
Mycoplasma
101
Stain purple, thick layer of peptidoglycan
Gram positive
102
Stain pink or red; thin peptidoglycan and outer membrane
Gram negative
103
The structural polysaccharide in the cell walls of domain Bacteria prokaryotes
Peptidoglycan
