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
Ebola virus
-Contains RNA which is the blueprint for assembling new virus
-A person infected with Ebola virus will typically develop a fever, headaches, joint and muscle pain, a sore throat and intense muscle weakness
-Symptoms start suddenly between 2 after becoming infected
-Ebola virus kills 90% of victims
-Breakout was in 2014
Human immunodeficiency virus (HIV)
-HIV contains two copies of single-stranded RNA which are transcribed into double-stranded DNA (by reverse transcription)
-It damages cells in the immune system and weakens your ability to fight everyday infections and diseases
-Most people experience a short flu-like illness 2 to 6 weeks after HIV infection, which last a week or two
-After the symptoms disappear, HIV may not cause any symptoms for many years later although the virus continues to damage the immune system.
Controlling disease
-Identifying contacts
-Rapid identification
-PPE
-Sterilising and disposing
-Avoiding contact
-Lockdowns
-Isolation
-Hygiene
-Social distancing
-Vaccines
-Vaccine passports
Developments of medicine
-Takes up to 10 years
-Costs millions of pounds
-Involves many scientists and doctors
Step 1 in developing medicines
(initial ideas)
Initial ideas come from:
-genome analysis
-computer modelling
-clinical compound banks
-medicinal plants
Step 2 in developing medicines
(research)
Go through research and testing on:
-cell and tissue cultures
-safety analysis
-molecular modifications
Step 3 in developing medicines
Animal testing is carried out to ensure it works in an organism and it is safe.
Step 4 in developing medicines
Three phases of human testing to further ensure safety and that the drug works (lots of complex regulation and licensing procedures).
Step 5 in developing medicines
Drug reaches the doctors surgery
Duration of each step in developing medicines
-Early phase research (4-6 yrs)
-Preclinical testing (1 yr)
-Clinical trials (3 phases; 6-7 yrs)
-Regulatory review
-Scale up to manufacturing (0.5-2 yrs)
-post market surveillance (continuous).
Vaccines and how they work
-Provides immunity
-Prevents disease outbreak
How antibiotics work:
-target the receptors by which the viruses recognise their host cells
-target the enzymes that help to translate or replicate the viral DNA or RNA
-inhibit the protease enzymes that enables new virus particles to bud from the host membranes
Process of Gram staining
1) Stain culture with crystal violet. Remove and rinse with water
2) Add iodine solution and remove after 1 minute
3) Add alcohol
4) Counterstain with red safranin for 1 minute
5) Dry and examine sample under microscope
