Antibiotics Definition: What is their function & mechanism of action

Antibiotics are the some of the most valuable and indispensable drug molecules in the present world health care system. Many people survive from deadly infectious diseases like tuberculosis, tetanus, septicemia, typhoid etc. due to use of these antibiotics.

There are many antibiotics for use and they are selected based on the prior experience or by antibiotic sensitivity test for the said infection. Yet there are bacteria which develop resistance to most antibiotics which is alarming to the medical world. Use of antibiotics greatly decreased untimely mortality of many infected patient.

# antibiotics

Antibiotics Definition:

Antibiotics are natural or semi-synthetic molecules which in small concentrations destroy bacteria and other microbes in the body.

Their specialty is they kill the microbes without affecting the body into which they were administered. This is again due to specificity or selectivity for the bacteria and not the body of administration.

Function & mechanism of action of these antibiotics:

Antibiotics especially kill bacteria and hence this creates their selectivity. Bacterial cell has different physiology and  anatomy than human and animal cells.

  1. Attacking and damage to cell wall : Antibiotics like penicillin, cephalexin damage the cell wall of bacteria. Human cells don’t have cell wall hence these are not affected. These antibiotcs cause pores in the cell wall which can lead to osmosis due to excess influx of water so that cell swells or loss of water so that cell shrinks and thus cell is burst & damaged.
  2. Attack on ribosomes & inhibit their growth and multiplication: Tetracycline, streptomycin etc antibiotics specially attack bacterial ribosomes and inhibit protein formation. Thus bacteria don’t grow and multiply and are killed. Human cell ribosome is different from bacterial ribosome and hence they are not affected. (Bacteria ribosomes have 70’S ribosome while animals and plants have 80’S ribosomes).
  3. Attack DNA synthesis; Antibiotics like ciprafloxacin, oflaxacin etc. attack DNA related enzymes of bacteria which are quite different from those of humans and hence kill them without harm to our body.


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