Antibiotics

Need to know

What you need to know

• **Inhibition of Cell Wall Synthesis:** This is a common target as eukaryotes lack a peptidoglycan cell wall. Antibiotics like penicillin and vancomycin interfere with the synthesis of peptidoglycan, weakening the cell wall and causing the bacterium to lyse (burst) due to osmotic pressure.
• **Inhibition of Protein Synthesis:** Bacteria have 70S ribosomes, while eukaryotes have 80S ribosomes. Antibiotics like tetracyclines, streptomycin, and erythromycin can specifically bind to bacterial 70S ribosomes and disrupt protein synthesis, halting bacterial growth and replication.
• **Inhibition of Nucleic Acid Synthesis:** Some antibiotics interfere with enzymes essential for DNA replication or transcription in bacteria, such as DNA gyrase. Quinolones (e.g., ciprofloxacin) are an example.
• **Disruption of Cell Membrane Function:** Antibiotics like polymyxins can disrupt the structure of the bacterial cell membrane, increasing its permeability and causing leakage of essential cellular contents. This mechanism is less common as eukaryotic cell membranes are similar, leading to lower selective toxicity.
• **Inhibition of Metabolic Pathways:** Some antibiotics, like sulfonamides, block essential metabolic pathways in bacteria that are absent in humans. For example, they inhibit the synthesis of folic acid, which bacteria must produce themselves, while humans obtain it from their diet.

Explanation

Antibiotics

1. **Inhibition of Cell Wall Synthesis:** This is a common target as eukaryotes lack a peptidoglycan cell wall. Antibiotics like penicillin and vancomycin interfere with the synthesis of peptidoglycan, weakening the cell wall and causing the bacterium to lyse (burst) due to osmotic pressure.
2. **Inhibition of Protein Synthesis:** Bacteria have 70S ribosomes, while eukaryotes have 80S ribosomes. Antibiotics like tetracyclines, streptomycin, and erythromycin can specifically bind to bacterial 70S ribosomes and disrupt protein synthesis, halting bacterial growth and replication.
3. **Inhibition of Nucleic Acid Synthesis:** Some antibiotics interfere with enzymes essential for DNA replication or transcription in bacteria, such as DNA gyrase. Quinolones (e.g., ciprofloxacin) are an example.
4. **Disruption of Cell Membrane Function:** Antibiotics like polymyxins can disrupt the structure of the bacterial cell membrane, increasing its permeability and causing leakage of essential cellular contents. This mechanism is less common as eukaryotic cell membranes are similar, leading to lower selective toxicity.