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Immunology - 3.1 - Coggle Diagram
Immunology - 3.1
ANTIBIOTICS
- A chemical produced by a microorganism that:
- kills bacteria (Bactericidal)
- Inhibits replication/growth of bacteria (Bacteriostatic)
- Antibiotics don't interfere with eukaryotic cell metabolism and therefore are safe to use in humans for bacterial infections
- Broad Spectrum - Antibiotic that can treat gram positive and gram negative bacterial infections
- Narrow Spectrum - Antibiotic that only act on some bacteria
Determining the effectiveness of antibiotics:
- Make a lawn or pour plate of the bacterial species you are investigating
- Place discs of different strengths of one antibiotic/different antibiotics onto the surface of the agar/lawn plate
- Incubate the plate at 25 degrees Celsius for 48 hours to allow bacterial growth
- Measure the size of the clear zone where the bacteria have not grown/been killed
- If the antibiotic has an effect there will be a clear sone around the disc. The larger the clear zone, the more bacteria have been killed/inhibited, the more affective the anitbiotic
Penicillin:
- Penicillin binds to and inhibits the enzyme responsible for the formation of cross links between the molecules of peptidoglycan chains
- Prevents the formation of cross links in the peptidoglycan of the cell wall during the growth and division of bacterial cells.
- This means that the cell wall is weakened, so when osmotic changes occur, water enters the bacterial cell and they lyse
- The cell dies when it lyses so penicillin is a bactericidal antibiotic
- Gram negative bacteria is generally more resistant to penicillin due to the outer lipopolysaccharide layer, which hinders the entry of the drug (also why this type of bacteria is more resistant to lysozyme tears)
- Humans don't have peptidoglycan in their bodies, so penicillin doesn't affect human cells only bacterial ones
Tetracycline/Doxycycline:
- Antibiotic that inhibits the translation stage of protein synthesis
- Tetracycline acts are a competitive inhibitor of the second anticodon binding site of the 30s subunit of bacterial ribosomes, and prevents the binding of a tRNA molecule to its complementary anticodon
- Tetracycline is a bacteriostatic antibiotic
- Broad spectrum antibiotic because protein synthesis is a metabolic process common to all bacteria
- Don't affect eukaryotic cells because eukaryotes have 80s ribosomes and so binding cant occur over the 40s subunit
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VIRUSES
- Genetic material (DNA/RNA) surrounded by a protein coat (capsid)
- Viruses are unaffected by antibiotics because they don't have a cell wall or carry out protein synthesis.
- Viruses don not carry out metabolic processes
ANTIBIOTIC RESISTANCE
Why does antibiotic resistance occur?
- Bacteria divide rapidly under optimum conditions and have a high mutation rate (A DNA copying error can lead to a mutation)
- Any mutation to a gene that the causes a protein to be made that can remove the effect of an antibiotic is said to confer a selective advantage to the bacteria in the presence of an antibiotic
- Therefore the overuse of antibiotics has resulted in the accidental selection of bacteria which are unaffected by some antibiotics
- Vertical transmission - by binary fission and horizontal transmission - conjugation in booklet - LOOK AT
How antibiotic resistance arises:
- Any bacterial population will include variants with unusual traits due to a mutation
- When a person takes and antibiotic, sensitive bacteria die
- Any antibiotic resistant bacteria are unaffected and continue to grown and multiply
- A population of antibiotic resistant bacteria has evolved
- The resistant bacteria can exchange genetic material with other bacteria, passing on the genes for resistance
- The antibiotic initially used against the bacterial strain will now be ineffective
Antibiotic resistant bacteria are more likely to occur if:
- Antibiotics are prescribed for trivial infections
- Antibiotics are prescribed for viral infections
- Patients do not complete a prescribed course
- Overused routinely/used by farmers
PROKARYOTES - BACTERIA
- Circular DNA (not surrounded by a nuclear envelope)
- 70s ribosomes
- No membrane bound organelles
- Naked DNA - not associated with histone proteins
Parts of a bacteria:
- Cell membrane
- Cell wall
- Slime capsule
- Ribosomes
- Pili
- Cytoplasm
- Plasmid/Circular DNA
- Flagellum
CELL WALL
- Prevents lysis due to osmotic lysis
- Made of peptidoglycan (N - acetylglucosamine (NAG) and N - acetylmuramic acid (NAM) alternated in long chains
- The chains are cross linked with amino acid side chains, this linkage gives strength to the cell wall