Communicable disease

Question 1

Tuberculosis

Answer 1

Bacteria
Kills cells and tissues, usually affects lungs

Question 2

Bacterial meningitis

Answer 2

Bacteria
Swelling of membranes surrounding brain and spinal cord, causing nerve or brain damage

Question 3

Ring rot

Answer 3

Bacteria
Ring of decay in potato or tomatoes, also wilting of leaves

Question 4

HIV

Answer 4

Virus
Attacks cells in immune system, causing a compromised immune response

Question 5

Influenza

Answer 5

Virus
Attacks respiratory system, causes headaches and muscle pains

Question 6

TMV

Answer 6

Virus
Discolouration of leaves

Question 7

Black sigatoka

Answer 7

Fungal
Leaf spots on banana plants, reducing yield

Question 8

Blight

Answer 8

Protist
Affects leaves + potato tubers

Question 9

Ringworm

Answer 9

Fungus
Growth of fungus in skin causing rash (cattle)

Question 10

Athletes foot

Answer 10

Fungus
Growth under skin of feet

Question 11

Malaria

Answer 11

Protist
Parasite in blood causing headache, fever, coma or death

Question 12

4 means of transmission

Answer 12

-direct physical contact
-faecal-oral transmission (eating contaminated things)
-droplets in air
-transmission by spores

Question 13

Malaria life cycle

Answer 13

-Person with malaria has plasmodium in blood
-female anopheles mosquito sucks blood
-plasmodium develops and migrates to salivary glands
-uninfected person is bitten
-plasmodium migrates to liver then the blood

Question 14

Plant physical defences

Answer 14

-cellulose cell wall
-lignin thickening of cell walls making them almost completely indigestable
-waxy cuticles, prevent water collecting on surface
-bark
-stomatal closure
-callose-blocks the flow in the sieve tubes
-tylose- balloon like swelling that blocks xylem

Question 15

Plant chemical defences

Answer 15

-terpenoids-essential oils that have antibacterial/antifungal properties
-Phenol- also have antibacterial/antifungal properties
-alkaloids-bitter taste to inhibit herbivores
-hydrolytic enzymes- eg. chitinase which breaks down chitin in fungal walls

Question 16

Necrosis

Answer 16

deliberate cell suicide to prevent pathogen spreading to the rest of the plant

Question 17

Canker

Answer 17

sunken necrotic lesion in woody tissue which causes death of cambium tissue in bark

Question 18

Blood clotting
7 steps

Answer 18

1.damage to vessel exposes lumen to collagen
2.platelets that come into contact with collagen change from discs to spheres with projections
3.shape change causes platelets to stick to RBCs + collagen, which releases chemicals for vasoconstriction
4.platelets release thromboplastin which triggers clotting cascade
5.thromboplastin causes conversion of prothrombin to thrombin
6.thrombin converts fibrinogen to insoluble fibrin
7. fibrin traps platelets + RBCs so endothelial cells can line the vessel

Question 19

Primary defences in animals

Answer 19

Skin
Blood clotting
Mucus membranes
Coughing + sneezing
Inflammation
Enzymes in tear fluid
Wax in ears

Question 20

Secondary non-specific defences in animals

Answer 20

Opsonins- unspecific antibodies that aid phagocytosis
Phagocytes-neutrophils, macrophages

Question 21

Neutrophils

Answer 21

-multi-lobed nucleus
-manufactured in bone marrow
-contain large amounts of lysosomes
-collect in area of infection causing pus

Question 22

Macrophages

Answer 22

-larger than neutrophil
-manufactured in bone marrow
-travel in blood as monocytes
-monocytes travel to lymph nodes and mature into macrophage
-macrophages don’t fully digest pathogens, the antigen from the pathogen is saved and the cell becomes an antigen presenting cell

Question 23

Types of T lymphocytes

Answer 23

T helper- release cytokines to stimulate phagocytosis
T killer- attack and kill host cells
T memory- provide long term immunity
-T regulator- shut down immune response when pathogen has died

Question 24

Types of B lymphocytes

Answer 24

Plasma- manufacture and release antibodies
B memory cells- act as immunological memory

Question 25

Specific immune response

Answer 25

Clonal selection
-invading pathogen has specific antigens
-antigens detected by T and B lymphocytes as specific receptor molecules are complementary shape
Clonal expansion
-correct lymphocytes activated
-increase in number by mitosis
Differentiation
-B and T lymphocytes develop into different cells eg. plasma to produce antibodies

Question 26

Structure of antibodies

Answer 26

-variable and constant region
-light and heavy polypeptide chains held by disulfide bridges
-hinge region allows antibody to join to more than one antigen

Question 27

3 main groups of antibodies

Answer 27

Opsonins- non specific antibodies that bind to antigen so phagocytes can bind
Agglutinins- cause antibodies attached to antigens to clump or agglutinate ready to be engulfed
Anti-toxins- neutralise toxic molecules released by pathogens

Question 28

Primary and secondary response graph

Answer 28

Primary
-when pathogen is detected the immune system starts to produce antibodies.
-takes a few days for sufficient antibodies to be produced and combat the pathogen
Secondary
-B and T memory cells stay in the blood from first infection
-recognise the antigen and produce antibodies more antibodies quicker

Question 29

Vaccination

Answer 29

-deliberate exposure to antigenic material that is rendered harmless
-this activates immune system so memory cells remain in the blood

Question 30

2 types of giving vaccines

Answer 30

Herd vaccination
-provides immunity to all or most of the population at risk
-once enough people are immune, the disease can no longer spread
-need to vaccinate about 80% of population
Ring vaccination
-vaccinating all people in the immediate vicinity

Question 31

Different types of immunity

Answer 31

Natural- achieved through normal life processes eg. breast milk or exposure to disease
Artificial- medical intervention eg. vaccination
Active- immune system is activated and produces own antibodies eg. exposure to pathogen or injected with antigen
Passive- antibodies supplied from another source eg. breast milk or injection of antibodies