A technician heats a flask of nutrient broth to sterilise it before adding one chosen type of bacterium. Why is the broth sterilised before the bacterium is added?
To dissolve the nutrients, so the chosen bacterium can absorb them more easily
To warm the broth to the temperature at which the chosen bacterium grows best
To make the broth set into a firm jelly, so separate colonies can be counted
To kill microorganisms already in the broth, so only the chosen bacterium grows
282 exam-style questions on AQA GCSE Biology 1.1 Cell structure, covering 1.1.1 Eukaryotes and prokaryotes, 1.1.2 Animal and plant cells, 1.1.3 Cell specialisation, 1.1.4 Cell differentiation, 1.1.5 Microscopy, and 1.1.6 Culturing microorganisms. Each one has a worked solution and a mark scheme showing where the marks go.