BRAINCAKECell Membrane Agents
The cell membrane (plasma membrane) of a bacterium controls what enters and leaves the cell. It is a phospholipid bilayer, like the membranes of human cells, but its lipid composition is different. Gram-negative bacteria also have an outer membrane containing lipopolysaccharide (LPS).
Polymyxins, such as polymyxin B and colistin, are the main example of antibiotics that act on membranes. They are positively charged molecules with a fatty tail. The positive part binds to the negatively charged lipopolysaccharide of the outer membrane, and the fatty tail pushes between the phospholipids. This disrupts both the outer membrane and the cell membrane, making them much more permeable.
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Key terms in this lesson
- lipopolysaccharide
- A molecule of lipid joined to a carbohydrate chain, found in the outer membrane of Gram-negative bacteria, part of which forms an endotoxin.
More in Bacteria and Disease
- Broad-spectrum, Narrow spectrum, Bacteriostatic and Bactericidal
- Antimetabolites
- Protein synthesis Inhibitors
- Cell Wall Agents
- DNA Gyrase Inhibitors
- Antibiotic Resistance
- Creating Drug-Resistant Bacteria
- MRSA
All 30 lessons in Bacteria and Disease · All Edexcel A-level Biology topics