Topic 6 - LQC 3A And 3B Flashcards
How do bacteria reproduce?
Binary fission, asexual reproduction
What do they not make in this process that animal cells do?
Spindle fibres
B VS V: Where is a mesosome found? What is it?
Bacterial cell, Inner folding of the membrane
B VS V: Where is a slime capsule found? What is it?
Bacterial cell.
Protective outer layer, prevents dehydration
B VS V: Where is a flagella found? What is it?
Bacterial cell.
Movement
B VS V: Where is main circular DNA found?
Bacterial cell
B VS V: Where is a cell membrane found?
Bacterial cell
B VS V: Where is ribosome found? What is it? What size are they?
Bacterial cell
small 70S
site of translation
B VS V: Where are pilli found? 3 functions?
Aid movement
allow bacteria to attach to surfaces
involved in conjugation (cell to cell contact)
B VS V: Where is a plasmid found? What is it?
Bacterial cell
Small loop of DNA
B VS V: Where is a cell wall found? What is it made of? What does that determine?
Bacterial cell
Made of peptidoglycan
It’s composition makes bacteria either gram-positive or gram-negative
B VS V: Where is a capsid found? What is it?
Virus
Repeating protein sub units, to protect the nucleic acid (RNA or DNA)
B VS V: Where are enzymes found? What are they used for?
Virus, contain enzymes for replication processes
B VS V: Where are nucleic acid found? What are they?
Virus
RNA - single stranded
DNA - Double or single stranded
B VS V: Where is the envelope found? What is it?
Virus
Taken from host cell surface membrane, contains lipids and proteins.
Helps virus to attach to host cell and penetrate the cell surface membrane.
B VS V: Where are glycoproteins found? What are they?
Virus
Recognise by host immune system as non-self
Act as antigens
What do viruses require for reproduction?
HOST CELL - they lack the internal structures for growth and reproduction
What is cell lysis?
Cells swelling and bursting, releasing virus particles
Describe process of how viral particles are released?
- virus attaches
- virus inserts nucleic acid
- viral nucleic acids replicate
- viral protein coats synthesised
- new virus particles formed
- virus particles released due to cell lysis
Bacterial cells have no…. And no ….
Nucleus and other membrane bound organelles
What are the two classes of Bacteria, based on their cell walls?
Gram positive and gram negative
What happens to gram positive bacteria in presence of the stain?
Take up the stain, turn purple
What happens to gram negative bacteria in presence of the stain?
Reject the stain, pink
Why do gram positive bacteria retain the stain?
Only made up of cell wall and inner membrane
They have more peptidoglycan in their cell walls
Why does gram negative bacteria not retain the stain?
- more complex cell wall (containing lipopolysaccharides)
- thinner layer of peptidoglycan
- lipopolysaccharides is an endotoxin, which blocks dyes, detergents and antibiotics
- periplasmic space between cell wall and cell membrane
Describe the process of binary fission (7)
- DNA is replicated
- old cell wall begins to break down around the middle of the cell
- DNA is associated with the cell membrane
- cell pinches forming septum
- two identical daughter cells formed
- plasmids often divide at the same time
Time between divisions is generation time
Bacteria can reproduce by …
Binary fission and sexual reproduction
What are the three types of sexual reproduction bacteria can reproduce by?
- transformation
- transduction
- conjugation
Describe the process of transformation
– A bacterium takes in DNA from environment (shed by other bacteria / introduced to in lab)
– DNA is in form of circular DNA called plasmid
– it can be copied in the receiving cell and passed onto its descendants
Describe the process of transduction
– Virus transfers bacterial DNA from one bacterium to another
– viruses called bacteriophages are able to infect bacterial cells and use them as hosts
– after multiplying viruses assemble and remove portion of the host cells bacterial DNA
– when bacteriophage later infects new host cell, a piece of bacterial DNA is incorporated into genome of new host
Describe the process of conjugation
– DNA is transferred from one bacterium to another
– pilus allows donor to pull itself close to recipient, DNA is transferred between cells
– in most cases DNA is in form of a plasmid
Viral envelope contains …
- host protein and lipids
- viral proteins (glycoproteins, called antigens)
- VAPs, virus attachment particles
Two adaptations of a virus
- extremely small, easily get into body
- simple structure of protein coat and genetic material, withstand harsh conditions and retain infectivity
What are the six major transmission routes?
Inoculation, inhalation, fomites, direct contact, vectors, ingestion
Describe inhalation
Breathing in leopard drop which contains pathogen through airways. These were expelled from more respiratory tract of individual.
E.g. flu, cold
Describe Direct contact
Transfer of pathogen directly onto skin/physical barrier, due to close contact with infected person
Describe inoculation
Pathogen enters directly into body through a break in the skin, e.g. dog bite, tattoo
Describe vector
Another organism transferring the pathogen to another organism, e.g. mosquitoes and malaria
Describe ingestion
Contaminated food or drink bleeding to vomiting and diarrhoea, greatest risk from raw/undercooked food e.g. E. coli, salmonella
Describe fomites
Inanimate objects that carry pathogens from one host to another e.g
Four major barriers to entry of pathogens
Skin, mucosal membrane, gut flora, stomach acid
Describe how skin provide provides a barrier to pathogen entry
– Hard protein keratin outer layer preventing microorganism entry
– skin flora outcompetes and prevents colonisation by other bacteria, as microbes live on the skin
– skin can be breached by wounds, blood clotting helps prevent this
Describe how mucosal membranes provide a barrier to pathogen entry
- Mucus lines airways and gut, goblet cells produce mucus
- Mucus traps microbes and other particles, cilia beats mucus to throat where it swallowed or coughed up
- secretions from eyes and nose contain the enzyme lysozyme, it breaks down bacterial cell walls causing them to burst
Describe how stomach acid provides a barrier to entry of pathogens
- Contains hydrochloric acid, giving a pH of less than 2.0, optimum pH for the enzyme Pepsin
- This kills most bacteria enter with food or drink
Describe how gut flow provides a barrier to the entry of pathogens
– intestines contain friendly bacteria which we have mutualistic relationship with
– they aid digestion and outcompete pathogenic bacteria, for food and space
– bacteria also secrete chemicals to aid defence against pathogens
