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In this topic of IBDP Biology, we will learn about antibiotics.
Antibiotics
Definition: substances produced by some micro-organisms which are in some way lethal to other micro-organisms.
- Produced by moulds:
- Slow growing cells.
- Antibiotics provide competitive advantage against other micro-organisms;
- Usually bacteria - which grow fast.
- Purified forms of antibiotics are more or less harmless to most humans.
- Act on some aspect of the growth of micro-organisms.
- The metabolic pathways are different to human cells.
- Do not affect ordinary mammalian cells.
Penicillin
- First antibiotic to be developed.
- Several versions of Penicillin.
- Variations on a common formula.
- Produced by different strains of Penicillium spp.
- Or, by using different culture media.
- Or they can be synthesised.
- Differ in the efficacy and ease of use in different applications.
- When it comes to IBDP Biology, all inhibit the production of cell walls by bacteria:
- Bind to an enzyme, transpeptidase.
- Prevent synthesis of cross links between petidoglycan polymers.
- The bacteria die due to osmotic lysis.
- They are bactericidal, i.e. it kills the bacteria.
Other antibiotics
- Various other antibiotics have also been developed.
- Eg streptomycin:
- Produced by Streptomyces species.
- Discovered soon after Penicillin.
- When it comes to IBDP Biology, some are bacteriostatic, i.e. inhibit the growth of bacteria.
- Different modes of action:
- Interfering with bacterial protein synthesis:
- Streptomycin binds to ribosomes.
- Causes mRNA codons to be misread.
- Some interfere with nucleic acid synthesis.
- Interfering with bacterial protein synthesis:
Administration of antibiotics
- When it comes to IBDP Biology, different diseases are treated with different antibiotics.
- Strains of some bacteria are resistant to several antibiotics.
- Essential that antibiotics are not over administered.
- Antibiotic screening is used to select the most effective antibiotics for particular bacteria.
- Broad spectrum antibiotics:
- Effective against a wide range of bacteria.
- Eg tetracyclines and chloramphenicol.
- Narrow spectrum antibiotics:
- Effective against a few bacteria.
- Eg penicillin (effective against Gram-positive bacteria)
That's the end of this topic.
