IB Biology SL C3.2 Defence Against Disease Question Bank

Practise IB Biology SL C3.2 by tracing barriers, clotting, innate defence, adaptive immunity, vaccination and antibiotic-resistance evidence.

Exam points

identify skin and mucous-membrane barriers and trace thrombin conversion of fibrinogen into a fibrin clot
compare phagocytic innate defence with antigen-specific B-cell, T-cell and antibody responses
interpret vaccination or reinfection graphs using memory cells and faster secondary antibody responses
explain antibiotic selectivity and use mutation, selection or plasmid transfer to account for bacterial resistance
explain how HIV transmission and helper T-cell loss reduce B-cell activation, antibodies and immune protection

Covered syllabus points

C3.2.1—Pathogens cause infectious diseases C3.2.2—Skin and mucous membranes C3.2.3—Blood clotting C3.2.4—Innate vs. adaptive immune system C3.2.5—Phagocytes C3.2.6—Lymphocytes C3.2.7—Antigens C3.2.8—B-lymphocyte activation C3.2.9—Clones of plasma cells C3.2.10—Immunity from memory cells C3.2.11—HIV transmission C3.2.12—HIV infection and AIDS C3.2.13—Antibiotics C3.2.14—Antibiotic resistance evolution C3.2.15—Zoonoses C3.2.16—Vaccines and immunization C3.2.17—Herd immunity C3.2.18—COVID-19 pandemic data evaluation

[Maximum number: 3]

(a)

Define pathogen.

[ 1 ]

(b)

Explain why antibiotics are effective against bacterial diseases but not against viral diseases.

[ 2 ]

[Maximum number: 7]

People with the inherited disease hemophilia have a deficiency in one of the proteins that act as clotting factors in blood.

Explain how blood clotting occurs and the consequence for a person who has hemophilia.

Clotting process:
Blood clotting seals cuts in the skin.
Clotting factors are released from platelets.
Thrombin is activated.
A cascade reaction occurs with thrombin.
Thrombin causes fibrinogen to be converted to fibrin.
Fibrin forms a clot/blocks the cut/prevents blood from being lost.

Consequences of hemophilia:
If a person does not have enough clotting factors/has hemophilia, the clot will not form.
Pathogens can enter the body more easily.
Blood will be lost from a cut, affecting blood pressure / causing bleeding to death.
Loss of blood affects the amount of hemoglobin/ $\mathrm{O}_{2}$ carried around the body.
Reference to lifestyle / menstrual/birth problems, e.g. surgery or contact sports.

[7 max]

[Maximum number: 1]

Which cell type is part of the innate immune system?

Phagocytes

B-lymphocytes

T-lymphocytes

Helper T-cells

All question bank results loaded

Covered syllabus points

C3.2 Defence against disease question 1

Question (a)

Question (b)

C3.2 Defence against disease question 2

C3.2 Defence against disease question 3