Antibiotics, such as penicillin, are medicines that help to cure bacterial…

The idea

This statement defines antibiotics and their mode of action. Antibiotics are medicines that treat bacterial disease by killing infective bacteria inside the body or by stopping their growth, which allows the immune system to clear the infection. Penicillin is a well-known example; it interferes with bacterial cell wall formation, so growing bacteria burst and die. Because human cells do not have the same cell wall structure, penicillin can target bacteria without directly damaging human cells. Antibiotics are prescribed for bacterial infections such as some throat, chest, skin and urinary tract infections. They are not effective against viruses, so they cannot cure viral diseases such as influenza. The medicine must reach the site of infection at an effective concentration, often taken over several days as prescribed.

What earns the marks

• Antibiotics are medicines used to treat bacterial disease.
• Penicillin is an example of an antibiotic that damages bacterial cell walls.
• Antibiotics are effective against bacteria but not against viruses.
• Completing the prescribed course helps ensure the bacteria are cleared and reduces the chance of resistance developing.

Common mistakes and how to put them right

• Saying antibiotics kill viruses.

  Put it right by stating they act on bacteria and are ineffective against viruses.

• Believing antibiotics damage human cells in the same way as bacterial cells.

  Put it right by explaining that they target bacterial structures such as cell walls.

• Thinking antibiotics work instantly.

  Put it right by explaining that they kill or inhibit bacteria over time, so the course must be completed.

Exam tips

• Name penicillin as a specific example when describing antibiotics.
• Use the phrase 'killing infective bacteria inside the body' to show precise understanding.
• Link the action of antibiotics to bacterial cell structures to explain why they are selective.