communicable diseases

Question 1

bacterial infections

Answer 1

1. tuberculosis
   - lungs, bacteria kills cells/tissues + suppresses the immune system
2. bacterial meningitis
   - infection and swelling of membranes around the brain and spinal cord
3. ring rot
   - damage/decay of potato tubers + tomatoes

Question 2

fungal infections

Answer 2

1. athlete’s foot
   - skin of foot/ between toes
2. ringworm
   - skin of cattle, infectious grey rash
3. black sigatoka
   - destroys plant leaves

Question 3

viruses

Answer 3

1. HIV/ aids
   - attacks the immune system
2. Influenza
   - attacks the respiratory system
3. TMV
   - pattern of leaf discolouration

Question 4

protoctista

Answer 4

1. malaria
   - plasmodium parasite - fever leads to coma/death
   - hard to make vaccine because the Protoctista hide in red blood cells so are hard to detect, and they have 3 stages to their life which makes it more challenging
2. potato/tomato blight
   - hyphae penetrate into host cells in leaves/fruits

Question 5

animal direct pathogen transmission

Answer 5

• physical contact
• droplets
• contaminated surfaces
• eating or drinking
• spores

Question 6

animal indirect pathogen transmission

Answer 6

• vectors

Question 7

plant-pathogen transmission

Answer 7

• soil contamination
• contact
• root entry
• airborne transmission (spores carried through air)
• insects/ vectors

Question 8

factors which affect transmission

Answer 8

1. overcrowding
2. poor nutrition
3. climate change - new diseases + vectors
4. increased rainfall
5. socioeconomic factors
6. poor soil richness
7. warm damp conditions

Question 9

plant defences

Answer 9

PHYSICAL

1. waterproof lignin walls
2. waxy cuticles
3. guard cells
4. callose deposits in sieve tubes - blocks spreading
5. tylose - swelling which fills xylem - blocks spreading

ACTIVE

1. production of repellant chemicals
   - terpenoids - strong-scented, antibacterial properties
   - alkaloids - bitter taste, prevent eating
2. hydrolytic enzymes - break down pathogen cell walls

Question 10

PNSDAP

skin

Answer 10

• prevents entry of the pathogen
• skin flora of healthy microorganisms outcompete pathogens
• dead cells act as effective barriers

Question 11

PNSDAP

blood clotting

Answer 11

• site of damage
• platelets adhere to the site of damage
• clotting factors released as enzyme cascade is activated

Question 12

PNSDAP

wound repair

Answer 12

• scab forms

- new skin forms underneath (cell differentiation)

Question 13

PNSDAP

mucous membranes

Answer 13

• specialised epithelial tissue covered in mucous
• goblet cells secrete mucous which traps pathogen
• mucous contains hydrolytic enzymes which destroy bacterial and fungal cell walls
• cilia beat mucous into acidic stomach

Question 14

PNSDAP

expulsive reflexes

Answer 14

• coughing, sneezing

- ejects pathogens

Question 15

PNSDAP

inflammation

Answer 15

• swelling of infected tissue
• histamine released by cells causing vasodilation
• capillary walls more permeable to white blood cells

Question 16

SNSDAP

phagocytes

Answer 16

• engulf, digest and kill pathogens
• considered secondary because they only act after the pathogen has entered the body

neutrophils = most common phagocyte

1. recognises antigen on pathogen as foreign
2. engulfs pathogen
3. pathogen enclosed in vacuole - phagosome
4. phagosome combines with lysosome - phagolysosome
5. enzymes in lysosome break down and digest the pathogen
6. produces fragments which are combined with glycoproteins = MHC - major histocompatibility complex
7. MHC moves antigens onto its own surface producing antigen-presenting cells - APC’s

Question 17

antigen presentation

Answer 17

• so T and B lymphocytes can recognise and come into contact with the APC’s
• full specific immune response stimulated

Question 18

cytokines

Answer 18

• cell signalling, molecules that have a specific shape complementary to the shape of the receptor site of lymphocytes, they bind to their receptors
• stimulate phagocytes to move to the site of infection (specific immune response)

Question 19

opsonins

Answer 19

• tag to/mark invasive pathogen so that they can be recognised
• stimulates phagocytosis

Question 20

macrophage

Answer 20

type of phagocyte, responsible for detecting, engulfing and destroying pathogens
produced through differentiation of monocytes

Question 21

specific immune response

4 main steps

Answer 21

1. APC antigens bind to T helper cell receptors, activating the T helper cells.
   - clonal selection occurs of T helper and killer cells
   - for each type of cell, clonal expansion occurs = mass cell replication
2. T helper cells produce interleukins (cell signalling molecules) which activates B cells
   - clonal expansion of B cells
   - some B cells = B plasma cells which manufacture antibodies/ immunoglobins
   - some B cells = B memory cells which provide immunological memory
3. T killer cells attach to infected cells and secrete toxic substances into the cells, killing them
4. T regulator cells suppress and control the immune system by stopping immune responses post pathogen elimination and making sure body recognises self-antigens

Question 22

interleukins

Answer 22

cell signalling molecules

Question 23

autoimmune disease

Answer 23

the immune system doesn’t recognise its own antigens and attacks different parts of the body
e.g. Lupus, Arthritis

Question 24

anti-toxins

Answer 24

antitoxins bind to harmful substances/toxins released by pathogens and render them harmless

Question 25

agglutins

Answer 25

cross-linking between pathogens causes them to group together which means pathogens are more readily engulfed

Question 26

antibody regions

Answer 26

top of each branch of Y = antigen-binding site variable region = specific to antigen S-S disulfide bridges hold polypeptide together hinges between heavy and light polypeptide chains allow bending - bind to more than 1 antigen constant region - attachment to phagocytes

Question 27

natural active immunity

Answer 27

- natural response - production of antibodies - body brings about the response

Question 28

natural passive immunity

Answer 28

- foetus receives antibodies across the placenta | - foetus doesn't produce antibodies itself

Question 29

artificial active immunity

Answer 29

- vaccination | - antibodies produced by the body when foreign substance is introduced into the body

Question 30

artificial passive immunity

Answer 30

- antibodies from another organism are injected into the bloodstream of another * short-lasting

Question 31

vaccinations

Answer 31

provide immunity to specific diseases by exposure to harmless antigenic material - dead or inactivated bacteria - weakened strains - modified toxin molecules - genetically engineered antigens

Question 32

vaccination types (mass, herd, ring)

Answer 32

mass - prevent spread in the wider population herd - provides immunity to most/all of the population ring - people in the vicinity are vaccinated to prevent spreading

Question 33

parasite

Answer 33

- lives in the host - feeds on the host - harms the host

Question 34

bacteria and antibiotics

Answer 34

- some develop resistance - bacteria can't be immune because they don't have an immune system - they are unicellular only multicellular organisms can have an immune response

Question 35

T cells

Answer 35

matured in thymus ``` 4 types T killer T helper T regulator T memory ```