B5: Micro-organisms and disease in humans

• Structure and reproduction of micro-organisms

• The spread and control of disease

Structure and reproduction of micro-organisms

Candidates will be assessed on their ability to:

• understand that pathogenic micro-organisms are parasitic and they include all viruses and some bacteria, protozoa and fungi (B5.01)

• recognise the potential of micro-organisms for extremely rapid reproduction (B5.02)

• recall the structure of a virus, including DNA or RNA core and protein coat, and that viruses lack some basic processes common to most living organisms (B5.03)

• understand that replication of viruses takes place by:

— injection of viral DNA into host cell

— the control of protein manufacture by viral DNA

— the production of new viruses

- the destruction of host cell and escape of new viruses which can then attack new host cells (B5.04)

• recall the structure of a bacterial cell including single chromosome (nucleoid), cytoplasm (in some cases including plasmids), surface membrane and wall (B5.05)

• understand that bacteria reproduce by cell division (mitosis) and that some bacteria form spores when unfavourable conditions arise (B5.06)

• recall that these spores are resistant to low temperature, high temperature, change in pH, desiccation and the effect of chemicals, and that they can grow into new bacterial cells if favourable conditions return (B5.07)

• recall the structure of fungi, including mycelium of branched hyphae with nuclei, cytoplasm, surface membrane and wall; understand that reproduction is by spore production (B5.08)

• recall the structure of yeast and understand that it reproduces by budding (B5.09)

• recall the word equation for anaerobic respiration in yeast:

glucose —> ethanol + carbon dioxide and energy released (B5.10)

• understand the effect of temperature, food supply and the build-up of toxic waste products on the rate of reproduction of bacteria and fungi (including yeast); evaluate data relating to potential and actual population growth in micro-organisms (B5.11)

The spread and control of disease

Candidates will be assessed on their ability to:

• recall that infectious diseases are caused by pathogens (B5.12)

• understand the importance of safe drinking water (B5.13)

• understand that pathogens are spread in various ways:

- in water (cholera bacterium) or food (Salmonella bacterium)

- in air (influenza virus)

- by contact (athlete's foot fungus)

- by body fluids (hepatitis B virus)

-- by animal vectors (housefly: dysentery bacterium; Anopheles mosquito: malarial protozoan) (B5.14)

• recognise the impact of global travel on the spread of disease and distinguish between the terms epidemic and endemic (B5.15)

• explain the importance to the individual and to the community of personal hygiene measures in preventing disease (B5.16)

• describe the causative agents, symptoms, methods of transmission and means of control of malaria and influenza (B5.17)

• understand that sterilisation can be achieved by the use of heat, chemicals (including chlorine) and irradiation (B5.18)

• distinguish between antiseptics and disinfectants and explain their different characteristics and applications (B5.19)

• explain the 'flash' process for milk pasteurisation; interpret data from experiments to investigate the effectiveness of pasteurisation (B5.20)

• explain the treatment of sewage by the 'activated sludge' method, including the part played by the respiration of aerobic bacteria and of anaerobic bacteria, producing methane; label a diagram showing this sewage treatment process (B5.21)

• understand that food poisoning is caused by various pathogens including Escherichia coli and Salmonella (B5.22)

• explain how intensive methods of animal rearing may result in the spread of Salmonella bacteria (B5.23)

• describe how Salmonella bacteria in meat and eggs reproduce quickly in warm storage
conditions and produce toxins which have harmful effects in the human gut (B5.24)

• explain methods of avoiding food poisoning by Salmonella including improved animal rearing, suitable food storage and cooking techniques (B5.25)

• understand the danger of consuming irradiated food in which micro-organisms have been killed but which may still contain their toxins (B5.26)

• explain the roles of phagocytes and lymphocytes in the body's defence against micro-organisms (B5.27)

• describe the role of memory B lymphocytes in secondary responses to antigen; interpret data showing variation in blood antibody levels in response to first and subsequent infections (B5.28)

• describe the production of monoclonal antibodies (technical details of the processes are not required) (B5.29)

• understand the principles behind the use of monoclonal antibodies (B5.30)

• recall that antibiotics are produced by some micro-organisms and describe their effects; evaluate data relating to the effectiveness of different antibiotics (B5.31)

• recall that penicillins are a major group of antibiotics, produced by a number of genetically different strains of the fungus Penicillium (B5.32)

• understand that penicillins prevent cell wall manufacture in a wide range of bacteria and are bactericidal (B5.33)

• describe and explain the technique for producing penicillin in an industrial fermenter; interpret and label a diagram of such a fermenter (B5.34)

• understand the limitations of the use of antibiotics:

- the reasons for their ineffectiveness against viruses

- the problems arising from their over-use, in terms of the rapid evolution of resistant strains of bacteria by mutation and natural selection (B5.35)
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