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Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.


A chemical which can destroy microorganisms. Antiseptics are applied to the surface of the skin or to living tissue to reduce the possibility of infection.


Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus


The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell


The basic unit from which all living organisms are built up, consisting of a cell membrane surrounding cytoplasm and a nucleus.


Fungi (singular fungus) are either uni-cellular, as in yeasts, or multi-cellular, as in mushrooms, toadstools and moulds. Fungi have a nucleus, cytoplasm and a cell wall



Chemicals v pathogens

Ever since people realised that infectious diseases are caused by organisms such as bacteria, fungi and viruses, they have been trying to kill off the pathogens. Many different types of chemicals have been tried, some with more success than others. Chemicals which can destroy microorganisms such as bacteria, fungi or viruses and stop them infecting other people are known as antimicrobials. Successful antimicrobials include:


Chemicals such as bleach which can destroy bacteria, fungi and viruses. They are usually very toxic (poisonous). This means they can be used on surfaces and objects but not on the skin or inside the body. They can prevent the spread of infection from food preparation surfaces, toilets etc.

Disinfectants keep surfaces clean.

Disinfectants keep surfaces clean
© iStock


Chemicals which can be used to destroy microorganisms on the surface of the skin but are too toxic to be taken into the body. They can prevent the spread of infection into the body from cuts and sores on the skin. Antiseptic hand washes can prevent the spread of infection from one person to another through skin contact.

Antiseptics keep your skin clean and help prevent the spread of infection.

Antiseptics keep your skin clean and help prevent the spread of infection
© iStock


Chemicals which can be used to destroy bacteria and fungi inside the body. Antibacterials such as penicillin are used to treat bacterial infections. Antifungals are used to treat fungal infections.

In the past hundreds of thousands of people died in the UK every year from infectious diseases. This included many young children. Antibiotics have saved millions of lives around the world since they were first discovered. Some commonly used antibiotics include penicillin, amoxicillin, chloramphenicol, erythromycin and vancomycin.

Antibiotics do not destroy viruses. Because viruses only reproduce inside other cells, it is very difficult to develop drugs that kill viruses without also damaging the body's tissues.

Antibiotics, and other antimicrobials, can be tested to find out how well they work to destroy bacteria. Discs of filter paper are impregnated with the antimicrobial and are placed on the surface of a petri dish containing agar pre-impregnated with bacteria. When the bacteria grow, the effectiveness of the antimicrobial can be seen.

Testing antimicrobials