Prokaryotic Cellular Structures and Functions Flashcards
Bacterial Cell Surface Structures, Cell Inclusions, Endospores, Bacterial Flagella and Locomotion, Taxes (25 cards)
Bacterial Cell Surface Structures
What is the difference between Pili and Fimbriae?
Pili - few in number and longer; used during conjugation and may have phage receptors
Fimbriae - shorter, surrounding periphery of the cell; aid in adhesion to host cell surfaces
They are both protein structures
conjugation (bacterial sex) - genetic process where exchange of bacterial DNA goes from one organism to another
Prokaryotic Cellular Structures and Functions
What are capsules and what do they do?
They are usually composed of polysaccharides and aid in adhesion to surfaces as well as help pathogens avoid phagocytosis and maintain hydration for the cell.
Prokaryotic Cellular Structures and Functions
What are Paracrystalline surface layes? Where are they found?
They are two-dimensional lattices of proteins or glycoproteins found in the cell wall of archaea. Their crystalline formation allows for small molecules to move across the S-layers.
Cell Inclusions
What are poly-B-hydroxy alkanoate (PHA) inclusions?
It is a lipid storage of carbon
this is for bacteria
- C4 form, poly-B-hydroxybutryate is the most common
- glycogen is another common storage molecule in bacteria
Cell Inclusions
What are inorganic molecule inclusions?
They are purple sulfur bacteria that can get energy from oxidizing H2S into S0 and store sulfur as granules in the periplasm.
These are gram-negative cells since they have a periplasm
Cell Inclusions
What are magnetotactic bacteria?
They are bacteria that contain magnetosomes that help orient themselves in magnetic fields.
Cell Inclusions
What are gas vesicles and how do they benefit phototrophic cells?
They are vesicles made up of protein and permeable to gas, but not water, so they allow planktonic bacteria to remain bouyant in the water. Phototrophic cells can use this to be closer to the sun and get more energy.
An example of a bacteria that does this, it cyanobacteria.
Cell Inclusions
How are the two proteins that make up the gas vesicle arranged to form such a water-impermeable structure?
GvpC - forms alpha helical cylinders that provide rigidy to the structure
GvpA - forms beta sheets that allow for gas molecules to come through, but not liquid molecules
If gas molecules can enter, how do they not leave?
Endospores
What are they?
They are differentiated forms of some bacteria that can withstand extremes of heat, chemical treatment, desiccation, and radition
- most resistant form of cell we know of
Endospores
When do they form?
what are the conditions?
They form during period of low nutrients, or other poor growth conditions and allow for survival and dispersion
Endospores
What are characteristics for endospores?
They may remain dormant for (possibly) thousands of years. They germinate when conditions are favorable, giving rise to normal, vegetative forms of the bacterium.
Dorminant meaning they are not germinating
Endospores
What are their structural features?
order of layers
Exposporium (loose fitting outer layer), core wall, spore coat, cortex (made of peptitoglycan), DNA
This is in order of most external to internal
Endospores
What are mechanisms of spore resistance?
Spore coat - protein layer that is protective against chemical damge
Lower water availability (cortex layer helps dehydrate the spore core)- confers heat resistance, less solvent to increase chemical resistance
calcium-dipcolinic acid - reduced water availbility and intercalates in DNA
SASP - bind tightly to DNA, converting it to a more compact and UV-resistant form (A-form)
intercalates - insert something between layers
SASP (small-acid soluble protein)
Endospores
What is binary fission?
Describe the process
It is a type of asexual reproduction where a single cell dividedes into two identical daughter cells.
steps - DNA replication, cell elongation, septum formation, completion of septum with formation of distinct walls, cell separation
septum - new cell wall that forms between daughter cells
Endospores
How are endospores formed?
- DNA replicates and denses
- asymmetric septum formation
- endospore septum grows around protoplast (developing endospore) - engulfment
- two membrane around spore
- dehydration
- exporium and primordial cortex form
- production of SASPs and diplicolinic acid; coat layers formed
- maturation - development of resistance to heat and chemicals
- lysis of cell and release of free endospores
Endospores
What happens when an endospore germinates
The spore inside the mother cell darkens b/c it looses refractivity. It then comes out as a rod shape and germination is complete.
Bacterial Flagella and Locomotion
What drives rotation of the flagellum?
proton motive force, about 1000 protons must cross the membrane for one revolution of the flagellum
Bacterial Flagella and Locomotion
What is the filament made up of?
flagellin subunits (protein)
Bacterial Flagella and Locomotion
What is the difference between reversible and unidirectional flagella?
reversible - countercockwise rotation to move forward and then counterclockwise motion to reverse
unidirectional - cockwise rotation to move forward, cell stops and reorients, counterwise rotation to move in another direction
Bacterial Flagella and Locomotion
What is the difference polar and peritrichous?
Polar flagella have the filament on either ends of the cell while peitrichous have the flagellum surround the cell or multiple bundled that can go in any direction
lophatrichus - tufted flagellum that are on end end
Bacterial Flagella and Locomotion
What is gliding motility?
- movement along a solid surface
- no flagella
Taxes
What is chemotaxis?
attractant towards chemicals
Taxes
What about phototaxis? aerotaxis? osmotaxis?
photo - moving in response to light concentration
osmotaxis - movement based on sodium concentration
aerotaxis - movement towaeds oxygen
Taxes
What causes a run versus a tumble?
Run is when flagellum are spinning and when they stop the movement they may tumble or twist around in the medium
