6.3 Defence against infectious disease

Essential idea: The human body has structures and processes that resist the continuous threat of invasion by pathogens.

Leukocytes are very varied in their structure and function. Above is just a few different types. Beyond leukocytes the body has other mechanisms such mucous membranes and barriers, e.g. the skin which help resist the invasion of pathogens.

Understandings, applications and skills

6.3.U1	The skin and mucous membranes form a primary defence against pathogens that cause infectious disease. [Diagrams of skin are not required.]
6.3.U2	Cuts in the skin are sealed by blood clotting.
6.3.U3	Clotting factors are released from platelets.
6.3.U4	The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin.
6.3.U5	Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases. [Subgroups of phagocyte are not required]
6.3.U6	Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity. [Subgroups of lymphocyte are not required but students should be aware that some lymphocytes act as memory cells and can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re-encountered.]
6.3.U7	Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells.
6.3.U8	Viruses lack a metabolism and cannot therefore be treated with antibiotics. Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance.
6.3.A1	Causes and consequences of blood clot formation in coronary arteries.
6.3.A2	Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
6.3.A3	Effects of HIV on the immune system and methods of transmission. [The effects of HIV on the immune system should be limited to a reduction in the number of active lymphocytes and a loss of the ability to produce antibodies, leading to the development of AIDS.]

[Text in square brackets indicates guidance notes]

Starters

Non-specific immune responses musically introduced by Mr W

A Scishow video on the five deadliest diseases in the world makes for a morbidly fun watch

Presentation and Notes

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Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Use the Cornell style template to collate your own notes for this topic.

Quick quiz

Quick quiz Use the BioK Quick Quiz on 6.3 Defense against infectious disease (as directed) to check your understanding of the topic.

Nature of science

Risks associated with scientific research - Florey and Chain’s tests on the safety of penicillin would not be compliant with current protocol on testing. (4.8)

Bringing this issue up to date is the TED talk 'In search of a cure for AIDs'. What are the ethical considerations of running human trials of retro-viral drugs?

International-mindedness

The spread and containment of diseases such as bird flu require international coordination and communication.