194 1 year, antibiotics are really used in clinic. 198 1 year, the definition of antibiotics should be: chemical substances produced by certain microorganisms, substances that can inhibit the proliferation of microorganisms and other cells.
Extended data
Antibiotics have four mechanisms:
1, inhibit the synthesis of bacterial cell wall.
Bacterial cell wall is located outside the plasma membrane, while human cells have no cell wall, which is why antibacterial drugs that inhibit the synthesis of bacterial cell wall are almost non-toxic to human cells.
2. Change the permeability of plasma membrane.
For example, nystatin combines with steroids in fungal cell membrane, destroying the structure of cell membrane. Amphotericin B, an antibacterial drug, can selectively combine with ergosterol in fungal plasma membrane, forming pores, changing membrane permeability, and leaking protein, amino acids and nucleotides in bacteria, resulting in bacterial death.
3, inhibit the synthesis of protein.
The synthesis of bacterial protein includes three stages: initiation, peptide chain extension and synthesis termination. It is completed by ribosome cycle in cytoplasm. Drugs that inhibit protein synthesis act on different stages of bacterial protein synthesis.
4, affect the metabolism of nucleic acid and folic acid.
Inhibition of transcription and replication of nucleic acid can inhibit the function of bacterial nucleic acid, and then prevent cell division and enzyme synthesis. Antibiotics that act in this way include nalidixic acid and dichloroacridine, rifampicin, etc.
Baidu encyclopedia-antibiotics