Disease

Question 1

Define disease

Answer 1

A condition that impairs the normal functioning on an organism. Can affect plants and animals

Question 2

Define pathogen

Answer 2

A microorganism that causes disease

Question 3

Define communicable and non-communicable disease

Answer 3

Communicable- A disease that can spread between organisms

Non-communicable-A disease that cannot spread between organisms

Question 4

Describe how viruses cause disease

Answer 4

-A virus attaches to a cell

-Viral DNA is injected into the cell

-Viral components assemble and form new viruses

-The viruses release which kills the cell

Question 5

Explain the to ways a communicable disease can be spread

Answer 5

Directly- From one organism to another through droplet infection, sexual intercourse or touching

Indirectly- Via an intermediate such as food, air, water or a vector

Question 6

State the type of pathogen TB is and what organisms it affects

Answer 6

A bacterial pathogen that affects animals, typically humans

Question 7

State the type of pathogen bacterial meningitis is and what organisms it affects

Answer 7

A bacterial pathogen that affects humans

Question 8

State the type of pathogen ring rot is and what organisms it affects

Answer 8

A bacterial pathogen that affects potatoes and tomatoes

Question 9

State the type of pathogen HIV/AIDS is and what organisms it affects

Answer 9

A viral pathogen that affects humans

Question 10

State the type of pathogen influenza is and what organisms it affects

Answer 10

A viral pathogen that affects animals and humans

Question 11

State the type of pathogen malaria is and what organisms it affects

Answer 11

A protoctist pathogen that affects animals and humans

Question 12

State the type of pathogen late blight is and what organisms it affects

Answer 12

A protoctist pathogen that affects potatoes and tomatoes

Question 13

State the type of pathogen black sigatoka is and what organisms it affects

Answer 13

A fungal pathogen that affects banana plants

Question 14

State the type of pathogen ring worm is and what organisms it affects

Answer 14

A fungal pathogen that affects animals and humans

Question 15

State the type of pathogen athlete’s foot is and what organisms it affects

Answer 15

A fungal pathogen that affects humans

Question 16

Name three social factors that can increase the spread of disease

Answer 16

-Overcrowding as it increases direct contact

-Poor healthcare as it isn’t as sterile which allows disease to spread

-Poor health education as people aren’t aware of the dangers of diseases

Question 17

How can climate affect the spread of disease?

Answer 17

-Late blight spreads best in wet summers as the spores need water to spread

-Malaria is common in tropical countries as vectors like mosquitoes breed easily there

Question 18

Explain 3 physical plant defences

Answer 18

Thick waxy cuticle- prevents diseases from making contact with the plant

Cell wall- helps prevent cells from being infected

Callose- deposits polysaccharide between cell walls and membranes when a plant is infected which prevents pathogens from entering the cell

Question 19

What are 2 chemical plant defences

Answer 19

Antimicrobial chemicals- Kill or inhibit the growth of pathogens such as saponins which destroy fungi membranes

Toxins- Produce chemicals that are toxic to insect pests that can transmit disease

Question 20

What are the 6 primary non-specific defences in animals?

Answer 20

Skin- Dry layer of dead cells that provide a physical barrier

Blood- Platelets enable clotting that prevents blood loss and entry of pathogens

Wound repair- Prevents entry of pathogens

Inflammation- Makes blood vessels more leaky

Expulsion reflexes- Coughing and sneezing expel foreign objects/pathogens

Mucous membranes- Found in mouth, nostrils, ears and prevents entry of pathogens Inflammation

Question 21

What is the secondary non-specific defences for animals?

Answer 21

White blood cells which consist of either lymphocytes or phagocytes

Question 22

Stat the two types of Phagocytes and describe them

Answer 22

Neutrophils:
-Have a multi-lobes nucleus and made in the bone marrow,
-Short lived and releases in large numbers when infection occurs
-Undertakes phagocytosis

Macrophages:
-Larger than a neutrophil and made in the bone marrow
-Display the antigens from pathogens on their surface
-Undertake phagocytosis

Question 23

Describe the process of phagocytosis

Answer 23

1) The phagocyte recognises the antigens on the pathogen surface,

2) Phagocyte engulfs the pathogen by infolding its membrane which forms a phagosome,

3) Lysosomes then fuse with the phagosome to form a phagolysosome,

4) Lysosomes then release their digestive enzymes called lysins to digest the pathogen,

5) The harmless products of this are then absorbed via active transport or facilitated/simple diffusion

Question 24

What is an opsonin?

Answer 24

Molecules in the blood that attach to the surface of pathogens to aid phagocytosis

Question 25

What is a cytokine?

Answer 25

Molecules in the blood that attract neutrophils via cell signalling, they are proteins

Question 26

What is a histamine and what is its function?

Answer 26

A histamine is a form of chemical messenger which is released when the body is infected with a pathogen, It makes your capillaries more leaky so that fluid enters your lymphatic system, As fluid enters the lymphatic system it takes pathogens with it where white blood cells can work on killing the pathogen

Question 27

What is a lymphocyte, what are three characteristics of one and what does it form?

Answer 27

A lymphocyte is a type of white blood cell, It has a large, round nucleus, 6-8μm which is smaller than a phagocyte, Has no granules in the cytoplasm, Forms B-lymphocytes and T-lymphocytes which can have 1000s of types as they have different receptors on the surface

Question 28

Explain what B-lymphocytes are

Answer 28

Start as immature B cells that develop from stem cells in bone marrow, Matures in the bone marrow which causes the cell to become larger and develop more receptors, Can differentiate into memory cells or plasma cells, Plasma cells are short lived and produce antibodies, Memory cells are long lived and provide immunity as the recognise pathogens which speeds up response time upon reinfection by producing other types of cells

Question 29

Explain what T-lymphocytes are

Answer 29

Start as immature T cells that develop from stem cells in the bone marrow, Matures in the Thymus which causes the cell to become larger and develop more receptors, Can differentiate into memory, helper, regulator or killer cells, Memory cells are long lived and are used to shorten response time during secondary reinfection by production other types of cells, Helper cells are short lived and produce chemicals (cytokines) which allow communication and coordination between other white blood cells. Also assist killer cells and stimulate phagocytes Regulator cells are short lived and are responsible for shutting down the immune response after the pathogen has been removed which prevents autoimmunity Killer cells are short lived and kill body cells that have been infected to prevent further spreading

Question 30

Explain the process of Primary immune response

Answer 30

Clonal selection- One cell is chosen to undergo clonal expansion and be replicated, Clonal expansion- The chosen cell is replicated through mitosis to produce many cells, Differentiation occurs- Cells will specialise into a specific type of cell to do a specific job, The cells then work together to kill the pathogen prevent disease

Question 31

Explain the process of secondary infection

Answer 31

Memory cells will recognise the pathogen and rapidly produce other types of lymphocytes and memory cells, This results in a faster response and a much higher concentration of antibodies to kill the pathogen