4.1.1 Communicable diseases, disease prevention and the immune system

Question 1

What is keratinisation?

Answer 1

keratinocytes at the surface of the skin dry out and the cytoplasm is replaced by keratin

Question 2

Describe the process of blood clotting

Answer 2

• Collagen exposed = Ca2+ ions and clotting factors are released from platelets which activate an enzyme cascade
• inactive thrombokinase = active thrombokinase
• prothrombin = thrombin
• soluble fibrinogen = fibrin
• platelets are trapped causing a clot, scab forms seal
• collagen deposited under and epidermis stem cells differentiate

Question 3

What is involved in inflammation?

Answer 3

• mast cells detect pathogen -> histamine -> vasodilation and make capillary walls more permeable to WBCs and proteins. Cytokines enhance phagocytosis
• blood plasma and WBCs enter tissue fluid = OEDEMA
• excess fluid drained = swelling of lymph nodes bc of lymphocyte production

Question 4

What is the role of reflexes?

Answer 4

air expulsion to remove microorganisms in response to irritation

Question 5

What is the role of mucous membanes?

Answer 5

goblet cells + glands secrete mucus to trap pathogens
stomach acid kills them
gut, ears, nose, airways

Question 6

Describe the role of neutrophils in phagocytosis

Answer 6

• large numbers, short lived
• binds to opsonin attached to antigen on pathogen
• phagosome formed from pseudopodia -> lysosomes fuse to form phagolysosome
• hydrolytic enzymes released

Question 7

Describe the role of macrophages in phagocytosis

Answer 7

• monocytes in blood
• don’t fully digest
• antigen saved and moved to special protein complex
  becomes ANTIGEN PRESENTING CELL
• increases chances that antigen will come into contact with lymphocytes

Question 8

What is clonal selection?

Answer 8

• activation of specific B/T lymphocytes

Question 9

Describe the mode of action of B lymphocytes ( HUMOURAL)

Answer 9

1. Antigen encountered
2. Interleukins released from T-cells and macrophages causes clonal expansion
3. Either differentiated into plasma cells to secrete antibodies (stimulated by monokines from macrophages)
4. OR differentiated into B memory cells for immunological memory

Question 10

Describe the mode of action of T lymphocytes ( CELL-MEDIATED)

Answer 10

1. T-helper cells recognise APC or antigen
2. Interleukins from T-cells and macophages causes clonal expansion
3. This then causes differentiation into T-helper cells (release cytokines to stimulate T-cells, B-cells and phagocytosis)
4. OR t-killer cells (interferon stimulates these) to attack cells
5. OR T memory cells that remain in blood for long time after primary response
6. OR t-regulator cells which shuts down immune response -> important in autoimmune disease

Question 11

What is the difference between primary and secondary response?

Answer 11

PRIMARY: delay since it takes time to recognise antigens, perform phagocytosis and for the specific response to be generated due to clonal selection time etc

SECONDARY: much faster clonal selection due to the B + T memory cells that remain in the blood after primary response. Antibody production starts sooner and is much more rapid, AND the maximum concentration is higher
They remain in the blood for longer too

Question 12

What is an autoimmune disease?

Answer 12

• own body cells recognised as antigenic and are attacked by the immune system e.g. arthritis
• genetic and environmental factors

Question 13

Describe the general structure of an antibody

Answer 13

they are IMMUNOGLOBINS - complex proteins.

2 light chains and 2 heavy chains
variable region which binds to antigen
constant region which stays the same, may have binding site for phagocytosis
hinge region to allow flexibility
disulfide bridges

Question 14

What is the role of opsonins?

Answer 14

bind to antigen and neutralise them, increase phagocytosis

Question 15

What is the role of agglutinins?

Answer 15

cross-link pathogens by binding to 2 antigens, each on same type of pathogen. it is impeded from imovement. increases phagocytosis also

Question 16

What is the role of anti-toxins?

Answer 16

bind to toxins, preventing them from entering cells

Question 17

Role of cytokines in phagocytosis?

Answer 17

attract phagocytes

Question 18

Outline how synthetic biology can be used in the provision of new medicines

Answer 18

• genetic modification of organisms
• to produce drug/ proteins/ vaccine

Question 19

State when each of the 5 things happen:

1. Antigen presentation
2. Clonal expansion
3. Clonal selection
4. High T-helper cell activity
5. Highest number of memory cells

A) 1st exposure to antigen
B) just after (rising antibody peak on graph)
C) as peak goes down
D) 2nd exposure to antigen
E) peak drifts off
F) line goes down more

Answer 19

1. A only (only 1st exposure)
2. B, D (occurs both times)
3. A (only occurs the 1st response - already have appropriate cells selected for 2nd response)
4. B, D (particularly helps with clonal expansion)
5. E (highest possible antibody peak)

Question 20

What is a pathogen?

Answer 20

Microorganism that causes disease

Question 21

How do bacteria cause disease? Examples?

Answer 21

Damage cells and release toxins

TB, bacterial meningitis, ring rot.

Question 22

How do fungi cause disease? Examples?

Answer 22

Hyphae forming a mycelium -> grow under skin and release enzymes and spores = irritation.

Athlete’s foot, black sigatoka, ring worm

Question 23

How do viruses cause disease? Examples?

Answer 23

takes over genetic machinery + host cell eventually bursts

HIV/AIDS
influenza
tobacco mosaic

Question 24

How do protoctista cause disease? Examples?

Answer 24

Feed on cell contents

Malaria, blight

Question 25

Which factors affect transmission ?

Answer 25

Factors: - hygiene e.g. hand washing, condoms - treatment of water -overcrowding - poor ventilation - poor health and diet - homelessness - living/working with migrants

Question 26

What is indirect transmission? What is an example? How does climate affect it?

Answer 26

using a VECTOR = another organism that may be used by pathogen to gain entry to primary host, or an intermediate e.g. MOSQUITOES (Anopheles) for malaria. Climate: mosquitoes, fungi, etc can reproduce more rapidly in warmer climates.

Question 27

How are plant pathogens transmitted?

Answer 27

- Soil -> esp if roots are damaged - Fungi produce spores = airborne - Pathogens in leaves spread when they shed, or in seeds - Insect attack, and transfer of bacteria/spores

Question 28

What are some examples of passive plant defences?

Answer 28

Lignin -> almost completely indigestible Stomatal closure Tylose fills xylem vessels and prevents spread Cellulose cell wall -> physical barrier Waxy cuticle Bark -> variety of chemical defences e.g. tannins Callose -> prevents spread in sieve tubes/ Also many chemicals with antipathogenic properties present before.

Question 29

What are some examples of active plant defences?

Answer 29

Cell walls thickened, callose deposited, oxidative bursts. Phenols : tannins in bark inhibit insect attack Alkaloids: N containing compounds - inhibit herbivores Terpenoids: antibacterial + antifungal properties Hydrolytic Enzymes Defensins: cysteine rich proteins with anti-microbial activity.

Question 30

What is a vaccination?

Answer 30

Deliberate exposure to antigenic material to stimulate an immune response

Question 31

What forms can a vaccination take?

Answer 31

- Whole live microorganisms,weakened version of a pathogen, dead pathogen, antigens from a pathogen , toxoid

Question 32

What is a herd vaccination?

Answer 32

- around 90% vaccinated. Disease can no longer spread = HERD IMMUNITY

Question 33

What is a ring vaccination?

Answer 33

vaccinating all near the new cases, also used to prevent spread of livestock disease

Question 34

Some pathogens can undergo ----- -> may not be recognised by ------- cells. E.g. ------ -------- may arise. Threats must be monitored so new ----- can be identified and ----- can be prepared. To avoid-------, people at risk are immunised. Worldwide research to determine which strains are likely to spread in a given year -> ------- programmes adapted.

Answer 34

mutations memory influenza epidemics strain vaccines pandemics immunisation

Question 35

What are antibiotics?

Answer 35

- Prevent bacteria/fungi growth - Most r derivatives of compound made by STREPTOMYCES bacteria - Over-use and misuse enabled resistance e.g. MRSA.

Question 36

What are the types of immunity?

Answer 36

Natural active: infection Artificial active: vaccination Natural passive: breast milk Artificial passive: antibody injection

Question 37

Why do we need new drugs?

Answer 37

- new diseases emerge - mutations - still many with no effective treatments - some antibiotics becoming less effective

Question 38

What is an example of accidental discovery?

Answer 38

- Fungus penicillium grew on petri dish and released compounds that killed bacteria

Question 39

How do traditional remedies lead to medicines?

Answer 39

- Plants/extracts now used in modern medicines - e.g. morphine from sap from unripe poppy seeds. Opium from poppies = anaesthetic. - Willow bark: relieve pain + fever. Active ingredient discovery -> add acetyl group -> reduces stomach bleeding -> led to aspirin and ibuprofen - therefore must maintain biodiversity

Question 40

How does wildlife and plant research lead to medicines?

Answer 40

- monkeys, bears rub citrus oils as antiseptics - birds line nests with medicinal leaves - can get inspiration from this - research used to isolate active ingredient so similar molecules can be manufactured

Question 41

Why is research into mechanisms useful?

Answer 41

- many diseases use membrane receptors e.g. HIV - if virus is blocked, pathogen cannot gain access - receptors are sequenced and modelling can determine shape once amino acid sequence is known - can find drug that mimics the receptor and binds to the virus - enzyme inhibitors can also be developed

Question 42

What is the use of synthetic biology and personalised medicine?

Answer 42

new molecules that mimic natural processes or use of natural molecules to produce new systems sequence genes of person with a particular condition and develop specific drugs

Question 43

Using examples, explain how both genes and the environment can cause animals to vary in their specific immune responses (6)

Answer 43

Genes: -inherit genes that code for immune cells and antibodies e.g. lymphocytes - different alleles code for different versions of immune cells/ antibodies - alleles code for many different variable regions - MHC alleles - mutation produces new alleles - ref to autoimmune diseases such as lupus Environment - exposure to diff pathogens determines immune response e.g. measles produce memory cells - vaccinations produce primary immune responses e.g. HPV by producing memory cells - environmental influence on allergies - poor diet can weaken immune system due to lack of vitamins - epigenetic changes due to stress/chemicals - autoimmune diseases with an environmental trigger such as AIDS

Question 44

Ash trees are an important part of the British landscape. In 2012, a fungal disease known as ash dieback arrived in UK from mainland Europe. Which of the following could explain how ash dieback could have reached the UK from mainland Europe? 1. Spores carried on wind 2. Young diseases trees imported from Europe and planted in UK 3. Contaminated soil from a previously infected crop A) 1,2 and 3 B) Only 1 and 2 C) Only 2 and 3 D) Only 1

Answer 44

B