6.3: Defence against infectious disease
Teaching time : 3 hours Practical time: 0 hours
NB - very helpful to review topic 6.2 before commencing this section of the course
key vocabulary
prior learning & retrieval practice
Review topic 2.4 proteins
Review topic 6.2 the blood system
Essential idea: The human body has structures and processes that resist the continuous threat of invasion by pathogens.
Exercise 1: Chalk-Talk in two phases:
What do the words "infectious disease" mean?
How do our bodies prevent them?
Exercise 2: Glossary of key terms: pathogen
Structures and processes that resist the invasion of pathogens
U1: The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
Skin and mucous membranes
Exercise 3: Copy and complete this word-cloze exercise, you can fill in the blanks from the following words: bronchi, cells, mucous, Keratin, sebaceous, oily, internal, primary, lysozyme ,water,
The skin and mucous membranes form a _______________ defence against pathogens that cause infectious disease.
External skin is composed of several layers of dead which act as a physical barrier to pathogens. The outer layers are Keratinised (contain the protein _______________) which makes them tough and impermeable to ________________.
glands in the skin secrete sebum, an substance which prevents the growth of bacteria and other organisms on the skin.
Mucous membranes are surfaces found in the human digestive system, respiratory system and reproductive system.
They are composed of thin linings of epithelial cells, protected by copious quantities of sticky which traps pathogens and contains , an enzyme that kills and digests pathogens.
Mucus membranes in the respiratory system contain cilia, organelles which waft the mucus out of the system to prevent the sticky mucus from blocking the _____________ and bronchioles.
Can pathogens get through the skin and mucous membranes? How? What happens if they do?
U2: Cuts in the skin are sealed by blood clotting.
U3: Clotting factors are released from platelets.
U4: The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin.
Blood Clotting
Exercise 4: Find the section of your textbook that explains blood clotting and connect-extend-challenge
Exercise 5: Glossary of key terms: clotting factors, platelets, cascade, fibrinogen, fibrin, thrombin
Exercise 6: Using the table below, create a flow chart that details the sequence of events in blood clotting
When clotting goes wrong
A1: Causes and consequences of blood clot formation in coronary arteries.
Exercise 7: Revision link to DP Topic 6.2 A3: Causes and consequences of occlusion of the coronary arteries. Review your notes from this section before proceeding.
Exercise 8: Using your textbook, create a table with the headings "causes" and "consequences" and the title "Causes and consequences of blood clot formation in coronary arteries. ". Bullet point your notes under each heading in your own words.
What happens when pathogens enter the tissues of the human body?
The non-specific immune system
U5: Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases.
Two types of immunity: non-specific and specific.
Exercise 9: Using a dictionary review the word "immunity". Add it to your glossary.
Review the terms endocytosis and exocytosis (revision link to topic 1.4) and add them to your glossary.
Phagocytic leucocytes
Exercise 10: Watch the You-tube video and connect-extend-challenge. (note some of the terminology here is more advanced than the DP Biology course).
Exercise 11: In your own words outline how phagocytic leucocytes give non-specific immunity.
The specific immune system
U6: Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity.
Antibody production
Exercise 12: Watch the You-tube video and connect-extend-challenge. (note some of the terminology here is more advanced than the DP Biology course).
Guidance from the syllabus: "Subgroups of phagocyte and 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."
Exercise 13: Answer the given IB question about antibody production (from the booklet question 3b and 4c)
HIV and the immune system
A3: Effects of HIV on the immune system and methods of transmission.
Guidance from the syllabus: :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.
Exercise 14: List the ways that HIV can be transmitted, horizontally and vertically.
Antibiotics
U6: Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells.
U7: 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.
A2: Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
NoS: 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)
Exercise 15: Using your textbook, research florey and chain's experiments to test penicilin and summarise them
