Disease

Question 1

Describe tuberculosis

Answer 1

• Bacteria
• Transmitted via airborne droplets and contaminated food and drink

Question 2

Name the 4 plant diseases and the type of pathogen that causes them

Answer 2

• Bacteria - ring rot (potatoes, tomatoes)
• Virus - tobacco mosaic virus (plants)
• Fungus - black sigatoka (bananas)
• Protoctista - potato/tomato late blight

Question 3

What is callose and how does it contribute to plant defence?

Answer 3

A polysaccaride deposited between the cell wall and plasma membrane to make it harder for pathogens to enter cells

Question 4

What chemicals do plant produce to defend themselves against pathogens?

Answer 4

• Insect repellents and insecticides - prevent insects from transmitting pathogens
• Antibacterial substances - to kill bacteria or inhibit their growth
• Toxins

Question 5

How does the skin act as a chemical barrier?

Answer 5

It produces sebum, which is an antimicrobial substance that lowers pH

Question 6

Briefly describe the process of blood clotting

Answer 6

Platelets release substance that, via a cascasde of events, result in the formation of fibrin which itself forms a network, trapping platelets and forming a clot

Question 7

How do damaged tissues trigger inflammation?

Answer 7

They release chemicals that dilate blood vessels and increase permeability of their walls

Question 8

What is the role of cytokines?

Answer 8

• Act as cell signalling molecules to trigger the movement of other phagocytes to sites of infection
• They can also stimulate an increase in body temperature

Question 9

How do specific defence mechanisms differ from non-specific?

Answer 9

• Specific are slower
• But provide a unique response for each type of pathogen and provide long-term immunity

Question 10

What is the function of T helper cells?

Answer 10

• Bind to APC’s and produce interleukins to stimulate B cells or phagoctyes
• Also form memory cells and T killer cells

Question 11

What is the function of T regulator cells?

Answer 11

Suppress the immune system after pathogens have been destroyed

Question 12

What are the different functions of cloned T cells?

Answer 12

• Develop into memory cells
• Develop into T killer cells
• Stimulate phagocytosis
• Stimulate division of T cells

Question 13

What is clonal selection and clonal expansion?

Answer 13

• Clonal selection - the process of selecting B cells with the correct antibody for cloning
• Clonal expansion - the division of specific to produce genetically identical clones

Question 14

What happens during the primary and secondary immune response?

Answer 14

• Primary - the concentration of antibodies increases slowly as B cells divide into plasma cells, which produce antibodies, and some divide into memory cells
• Secondary - the concentration of antibodies increases quickly as memory cells recognise the pathogens antigens and divide into plasma cells

Question 15

What are the functions of T and B memory cells?

Answer 15

• T memory - divide to form many T killer cells
• B memory - divide into plasma cells that can produce antibodies specific to a pathogens antigens

Question 16

How many polypeptide chains are antibodies made up of?

Answer 16

• Four polypeptide chains
• Two heavy and two light chains which are held together by disulphide bridges

Question 17

What are the constant, variable and hinge regions on antibodies?

Answer 17

• Constant - same for all antibodies and bind to receptors on cells
• Variable - different for each antibody and bind to specific antigens
• Hinge - allows the antibody to be flexible and bind to multiple antigens at once

Question 18

What is the role of antibodies in agglutination of pathogens?

Answer 18

They cause pathogens to clump together for easier phagocytosis

Question 19

Describe active immunity, and give an example of natural active immunity

Answer 19

• Active immunity develops when the immune system produces its own antibodies after exposure to a pathogen’s antigens
• Natural active when antibodies are produced after infection by a pathogen

Question 20

Describe passive immunity, and give an example of natural and artificial passive immunity

Answer 20

• Develops when an individual is given antibodies made by a different organism
• Natural passive when babies receive antibodies from their mothers through the placenta and breast milk
• Artificial passive when antibodies or toxins produced by one organism are injected into another organism

Question 21

What is an example of an autoimmune disease?

Answer 21

Arthritis

Question 22

What are some examples of substances vaccines may contain?

Answer 22

• Dead or inactivated pathogens
• Harmless toxins
• Isolated antigens
• Genetically engineered antigens

Question 23

What are antibiotics?

Answer 23

• Drugs that kill or inhibit the growth of bacteria
• They target bacterial enzymes and ribosomes used in metabolic reactions, which are different from human enzymes and ribosomes

Question 24

What are personalised medicines?

Answer 24

Medicines tailored to an individual’s DNA