Topic 2.2 Prokaryotic cells Flashcards
Pilli
-Short hair-like structures on the cell surface
-They have a role in movement
-Are more often involved in adherence to surfaces, which facilitates infection and is a key virulence characteristic.
Flagella
-Primarily used for cell movement
-Spins creating forward movement
-Some prokaryote have more than one flagella, localised to one pole or spread out around the cell.
70S ribosomes
-These consist of a 30S subunit and a 50S subunit
-The smaller subunit is comprised of more than 20 proteins
-The larger subunit comprised of more than 30 proteins
-Their main role is in protein synthesis.
Nucleoid
-The space within prokaryotic cell where the genetic information (genophore) is found
-It doesn’t contain a membrane.
Plasmids
-Small loops of DNA that are separate from the main circular DNA molecule
-Plasmids contain genes that can be passed between prokaryotes.
Capsule
-A final outlier that surrounds some prokaryotes
-Sometimes called slime capsule
-Helps to protect bacteria from drying out.
Peptidoglycan
-Found in bacterial cell wall
-Made up of many parallel polysaccharide chains with cross links that form a net like structure.
How to distinguish between the two bacterial cell walls?
A technique called gram staining
Gram (+) cell wall
Have a thick peptidoglycan layer which means that stains get trapped in the cell wall leading to deeper colour when stained.
Gram (-) cell wall
Have a thin layer of peptidoglycan which means the stain doesn’t get trapped so much during the process and they have a lighter colour.
General viral structure
-Acellular: not living
-Has a protein coat or capsid
-Some have a lipid envelope which covers the protein coat which makes it easier for viruses to pass from cell to cell.
Virus shapes
-Helical
-Polyhedral
-Spherical
-Complex
Virus classification
-Mode of replication (lytic, lysogenic)
-Genetic material
-Capsule structure
-Host organism
-Size
Lambda phage (λ) virus
-Lambda phage is a virus particle consisting of a head containing 48514 base pairs of double stranded linear DNA
-It infect the bacterial species Escherichia coli (E coli)
-Usually goes through the lytic cycle and lambda DNA assembles in its host.
Tobacco mosaic virus
-Contains single stranded RNA as its genetic material
-It infects mostly tobacco plants and other membranes of the family Solanaceae
-Causes the mosaic/mottling discolouration on the leaves