Prokaryotic Cells: Morphology, Cell Wall & Membrane Flashcards
T or F: All prokaryotes are phylogenetically related
False.
Archaea and Eukarya are more closely related.
Do prokaryotic cells contain a true nucleus?
No, but they have an nucleoid.
Bacterial Prokaryotic cell walls are made of _____, while
Archaic Prokaryotic cell walls are made of _____
peptidoglycan layer (bacteria) or pseudomurein (archaea)
Do Prokaryotes have organelles?
No. But eukaryotes do.
Prokaryotes have structures & parts, but not organelles.
What are the advantages of higher SV ratio in Prokaryotes?
- Utilization of nutrients: efficient & faster nutrient uptake
- Adaptability: #1 leads to population growth → DNA errors (mutations) → survive and adapt
Cell shape that allows movement in rotations (like tight corkscrews)
Spirochete
Give the names of these cell shapes
- spherical
- rod
- wavy
Cocci , bacillus, spirillum
Grape-like structure of cell arrangement
staphylo
Chain structure in cell arrangement
strepto
3 main parts of cell wall and membrane
Peptidoglycan layer
Outer membrane
Periplasmic space
Functions of cell wall
maintains cell shape &
prevents cell bursting
List
What are the main differences in G+ and G- bacteria?
(not regarding glycan tetrapeptide)
Bonus: How are they different?
5
[ + vs - ]
1. Peptidoglycan layer (90% vs 10%)
2. Outer membrane (absent vs present)
3. Texture (smooth vs rough)
4. Cytoplasmic membrane (thin vs thick)
5. Ethanol (blue purple vs clear)
not sure abt cytoplasmic membrane omfg maica pls edit when u know
Difference with Gram + and - with the peptidoglycan layer
Gram + is thick (90%) while Gram - is thin (10%)
Difference with Gram + and - with the outer membrane
[+] = absent
[-] = present & makes it look rougher
Difference with Gram + and - with the Periplasmic space
both present
Why are G+ bacteria smooth, while G- bacteria rough?
The outer membrane of G- has phospholipids and lipopolysaccharides
Difference with Gram + and - when ethanol is added
- = blue purple
- = clear
T/F [Bonus: If false, what is wrong?]
A Transmission Electron Microscope shows surface of cell, while
A Scanning Electron MIcroscope shows cross section of cell
False
TEM: cross section
SEM: surface
Sugar of Peptidoglycan Layers
N-acetylmuramic acid (M) &
N-acetylglucosamine (G)
True or False: Sugars of Peptidoglycan Layers of Gram + and - are the same
True
Linakages in the Peptidoglycan Layers
ꞵ-1, 4-glycosidic bonds
What are the 3rd amino acids for Gram + and - in peptidoglycan layer?
[+] = Lysine
[-] = DAP (diaminopimelic acid)
What are the peptido linkages for Gram + and -?
[+] = pentaglycine crosslink
[-] = none
Linkages are easily destroyed by ___
lysozymes
Explain
How do lysozymes destroy B-1,4-glycosidic bonds?
Lysozyme: First line of defense
2. Bacteria attacks body (ex. enters mouth)
2. Bodily fluids are in contact with bacteria
3. Lysozyme opens cell wall & breaks bond
3. Bacteria can’t attach anymore!
Where can lysozymes be found?
In bodily fluids like sweat, tears, and saliva
Why is it called Glycan Tetrapeptide?
Glycan - 2 sugars
Tetra - 4 amino acids
Linked together by peptide bonds
In the cell wall, what lies along the Y axis?
Peptide bonds for rigidity
In the cell wall, what lies along the x axis?
B-1,4-glycosidic bonds for stability and strength
T or F: the outer membrane can be found in both gram + and - organisms.
False. Only in Gram -
Where you would find the structure responsible for the toxicity of Gram - ?
Lipid A - where endotoxins are secreted
Why is Gram - more infectious that Gram +?
G- more capable of evading defense systems of hosts, antibiotics, etc.
Gram - has outer membrane that prevents entry of certain chemicals (like antibiotics)
Process of Gram staining?
- Fixation - heat to stick unto slide and kill bacteria
- Crystal violet - primary stain
- Iodine treatment - helps dye stick to cell
- Decolorization - dehydrate the cell
- Safranin - counterstain
Why does Gram + organism remain purple after gram staining?
The thick peptidoglycan layers retains the color from crystal violet.
What are the issues that cause ineffective gram staining?
- culture is too young
- dyes were not prepared correctly
- don’t spread it to too much because the cell will separate
Give the characteristics of Staphylococcus aureus
coccus - spherical
staphylo- - grape-like clusters
G+ - Purple
Characterisitics of Escherichia coli
bacillus-shaped / rod shaped
random (don’t have a definitive pattern)
G- Pink
Give examples of cell wall-less prokaryotes
Mycoplasma and Thermoplasma
Cell wall-less prokaryotes are able to exist because of ___ in their cytoplasmic membrane
sterols
Gram staining archaea will result in a gram ___ reaction
variable
What is gram variable?
Happens to domain archaea. Gram staining wont work because it may appear pink or blue.
What layer of cell wall in domain archaea makes honeycomb-like structures?
S- layer or pseudomurein
What are the sugars of cell wall in archaea?
N-acetyltalosaminuronic acid and
N-acetylglucosamine
What are linkages in the cell wall of archaea?
ꞵ -1, 3-glycosidic bonds
T or F: Linkages are easily destroyed by lysozymes in archaea cell walls.
False. not easily destroyed.
What is the difference with the sugars of domain bacteria and domain archaea?
Bacteria: N-acetylmuramic acid
Archaea: N-acetyltalosaminuronic acid
Amino acids of archaea are in _ forms
L forms
What part of the cytoplasmic membrane confers strength in bacteria?
Hopanoids
Highly selective barrier that facilitates nutrient transport but offers little protection against osmotic lysis
cytoplasmic membrane
What are cytoplasmic membranes composed of?
Glycerol - hydrophilic
Fatty acids - hydrophobic
T or F: In cytoplasmic membrane, the fatty acids are oriented outwards.
False. Fatty acids are oriented inwards and they protect each other from exposure from the aqueous environment.
In Bacteria, __ links fatty acids to glycerol
In Archaea, __ links fatty acids to glycerol heads
ester
ether
T or F: Ester links fatty acids to glycerol in Archaea
False. Ether for archaea
T or F: The lipid monolayer of archaea is easily torn apart.
False. Its the lipid bilayer of bacteria that is easily torn apart.
Give the 3 functions of cell cytoplasmic membrane
-
Permeability Barrier
- Allows passage of certain nutrients
- Prevents leakage of cell contents -
Protein anchor
- Where you find various proteins embedded involved in nutrient transport, bioenergetics, and chemotaxis -
Energy Conservation
- Site of energy conservation and consumption
- Proton motive force (propels the organism if it is capable of motility)
Cytoplasmic membrane is (blank).
Aquaeous
