antibiotics definitions: biology immunology

A-level biology, EDUQAS, option A: Immunology

Antibiotics

Produced by fungi (e.g: penicillin), inhibit/kill bacteria via interfering with peptidoglycan cell walls.

Antimicrobial

Compounds that generally inhibit the growth of bacteria.

Antiseptics

Antimicrobials that are used on/affect living tissue - including areas where the skin has been broken (cuts/grazes etc)

Disinfectant

Antimicrobials used on non-living tissue (e.g: bleach).

Broad spectrum antibiotics

Can affect many species of gram positive and gram negative bacteria.

Narrow spectrum antibiotics

Selectively affect species of gram positive bacteria due to their thick peptidoglycan cell wall.

Bactericidal

Antibiotics that KILL bacteria (e.g: penicillin destroying bacterial cell walls).

Bacteriostatic

Antibiotics that PREVENT THE MULTIPLYING of bacteria (e.g: inhibiting protein synthesis) — bacteria will reproduce once the antibiotic levels decrease.

Transpeptidase enzymes

Cross-link the polysaccharide molecules

Gram positive

Has a thick layer of peptidoglycan that makes up the bacterial cell wall. Stained by crystal violet.

Gram negative

Has a much thinner layer of peptidoglycan compared to gram positive bacteria

Gram staining

A process that involves adding crystal violet

Penicillin

One example of a narrow spectrum antibiotic:

Tetracycline

One example of a broad spectrum antibiotic:

Antibiotic resistance

Occurs when a few resistant bacteria survive antibiotic treatment and proliferate.

Bacterial conjugation

The exchanging of genetic material by swapping plasmids between bacteria.

Incomplete courses of antibiotic medication

A common reason for antibiotic resistance:

Plasmid DNA

Can be acquired by bacteria from different bacteria

Zones of Inhibition

Areas around the antibiotic on agar plates where the bacteria has been killed off/stopped from reproducing.

What should not be used on living tissue as it may cause more damage/harm?

Disinfectant

Sources of antibiotic resistance

Mutations and plasmids.

Why are mutations a key source of bacterial resistance?

Bacteria divide rapidly so have a high mutation rate, increasing the chance of obtaining an antibiotic resistant allele/gene