Antibiotics and bacterial enzymes By Helena, Issy and Jess

What are they? Antibiotics are chemicals that can kill or inhibit the growth of microorganisms. Antibiotics How do they work? Some antibiotics – eg. Penicillin inhibits the enzyme transpeptidase, which catalyses the formation of proteins in bacterial cell walls. This weakens the cell wall and prevents the bacterium from regulating its osmotic pressure. As a result the cell bursts and the bacterium is killed.

Resistance to Antibiotics Many forms of bacterial resistance occur because there may be a mutation and altered enzymes. These enzymes may be capable of inactivating antibiotics. This bacterium is naturally selected when the bacterial population is exposed to antibiotics. It will survive and then reproduce. Many strains of bacteria are resistant to penicillin because they produce betalactamase that breaks down the penicillin molecules.

How is it made? Repeating sub-units of polysaccharide materials form bacterial cell walls. Inhibition of the enzymes responsible for building the wall occurs because penicillin is structurally similar to one of the substrates used in the wall building. However, the penicillin molecules are different from the substrate – so the walls formed are weak and fall apart.

Classes of antibiotics… Penicillin Tetracycline Macrolide Cephalosporin