Antibiotics are medicines. They treat diseases caused by bacteria. They kill bacteria or stop them growing. They have no effect on viruses. A cold is caused...
Question 1 Report
Antibiotics are medicines. They treat diseases caused by bacteria. They kill bacteria or stop them growing. They have no effect on viruses. A cold is caused by a virus. When a doctor gives antibiotics, they give a full course. The patient should finish it. This is true even if they feel better first. Doctors are now worried. Some bacteria are no longer killed by the old antibiotics. These infections are much harder to treat. A student was asked how bacteria become resistant. The student was also asked how to slow this down. The questions below are about antibiotics and resistance.
(a) State why antibiotics are of no use in treating a cold. [2]
(b) Explain, using the idea of variation and natural selection, how a population of bacteria can become resistant to an antibiotic. [4]
(c) Explain why a patient is advised to finish the whole course of antibiotics. [2]
(d) State the term used to describe a strain of bacteria that is not killed by an antibiotic. [1]
(e) Suggest two ways in which the spread of antibiotic-resistant bacteria could be slowed down. [2]
Answer Details
This question tests the difference between bacterial and viral infections and, most importantly, how natural selection produces antibiotic-resistant bacteria.
(a) A cold is caused by a virus [1], and antibiotics only kill bacteria; they do not affect viruses [1]. [2]
(b) The evolution of resistance follows the steps of variation and natural selection [4]:
- Within the bacterial population there is variation; by chance a few bacteria carry a resistance allele produced by mutation [1].
- When the antibiotic is used it kills the non-resistant bacteria [1].
- The resistant bacteria survive and reproduce [1].
- They pass on the resistance allele to their offspring, so over generations the resistant form becomes more common in the population [1].
(c) Finishing the whole course makes sure that all the bacteria are killed [1], so that any slightly resistant ones are not left alive to survive and multiply [1]. [2]
(d) A strain that is not killed by an antibiotic is described as resistant. [1]
(e) Any two ways to slow the spread [2]: only use antibiotics when they are really necessary; always finish the prescribed course; do not use antibiotics for viral infections; maintain good hygiene to prevent bacteria spreading. (any 2)
Download The App On Google Playstore
Everything you need to excel in your exams
