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OCR A Level Biology > 4.1 Disease And The Immune System > Flashcards

4.1 Disease And The Immune System Flashcards

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1
Q

Name 4 groups of pathogen that can cause disease.

A

Bacteria
Virus
Protocista
Fungi

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2
Q

List three bacterial diseases and their methods of transportation.

A

Tuberculosis - airborne droplets (human)
Meningitis - airborne droplets (human)
Ring rot - direct contact (plant)

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3
Q

List three viral infections and their methods of transportation.

A

Influenza - airborne droplets (human)
HIV / AIDS - transfer of bodily fluids (human)
TMV - contact of leaves or vectors (plant)

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4
Q

List two protocist infections and their methods of transportation.

A

Malaria - female mosquitos (human)
Late blight - spores (plant)

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5
Q

How are communicable diseases pathogens transmitted directly ?

A

Inhalation of droplets
Skin to skin contact / exchange of fluids
Penetrate skin actively using enzymes / through wounds.

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6
Q

How are communicable diseases transmitted indirectly ?

A

Consumption of contaminated food / drink
Vectors
Spores

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7
Q

How do living conditions affect disease transmission ?

A

Overcrowding increases direct transmission
Climate determines what pathogens can survive
Social factors influence how quickly people are treated.

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8
Q

Name 3 physical barriers to pathogen entry in plants.

A

Cellulose cell wall
Lignified layer
Waxy upper cuticle

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9
Q

Describe 2 mechanical responses to infection in plants.

A

Guard cells close stomata
The polysaccharide callose is produced & placed between the cell wall and plasma membrane to increase entry distance.

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10
Q

What is necrosis ?

A

Injury of a plant activates intracellular enzymes that kill cells near site of infection to prevent spread

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11
Q

How do hydrolytic enzymes act as chemical defences in plants ?

A

Hydrolytic enzymes are found in the central vacuole and break down cell walls of invading organisms.

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12
Q

How do Terpenoids act as chemical defences in plants ?

A

Terpenoids are oils that act as antibacterials, killing bacteria.

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13
Q

How do Phenols act as chemical defences in plants ?

A

Phenols inhibit insects from attacking by interfering with digestion

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14
Q

How do alkaloids act as chemical defences in plants ?

A

Alkaloids deter herbivores from feeding as they taste bitter.

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15
Q

How do defensins act as a chemical defence in plants ?

A

Defensins inhibit transport channels of infected cells.

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16
Q

Name 5 barriers to pathogen infection in humans

A

Keratin layer in skin
Blood clotting prevents pathogen entry through wounds
HCl in stomach kills bacteria
Beneficial bacteria in gut and skin provides competition
Mucous membranes trap pathogens

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17
Q

What are expulsive reflexes ?

A

The body attempting to force foreign substances out
•Irritation of nostrils cause sneezing
•Irritation of of ciliated epithelial cells in lungs causes coughing

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18
Q

Name 4 ways the nonspecific immune system responds to infection.

A

•Inflammation
•Phagocytosis
•Digestive action of lysozymes
•Production of interferon (antiviral agent)

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19
Q

Outline the process inflammation.

A

Damaged tissues’ mast cells release histamines causing vasodilation
Blood flow and permeability of blood vessels increases
The mast cells also produce cytokines, which attract phagocytes to the effected area to undergo phagocytosis.

20
Q

How does blood clotting occur?

A

Blood platelets form plug and release chemicals that enhance plugging (thromboplastin)
Thromboplastin & CA2+ + Prothrombin-> Thrombin
Thrombin is an active enzyme which can now catalyse the following reaction :
(Thrombin +) Fibrinogen -> Fibrin
Fibrinogen is soluble, Fibrin is not
Fibrin makes a mesh which traps RBCs creating a thrombus (blood clot).

21
Q

Name the 2 types of white blood cells involved in phagocytosis.

A

Neutrophils
Macrophages (can become APCs)

22
Q

How does phagocytosis destroy pathogens ?

A

•Phagocyte moves towards pathogen which may have been marked by opsonins
•Phagocyte engulfs pathogen via endocytosis to form phagosome
•Phagosome uses lysosome to ingest pathogen

23
Q

Explain the role of antigen presenting cells (APCs).

A

•Macrophage displays antigen on its surface after pathogen is ingested
•Enhances recognition by Tʜ cells
•Secrete cytokines that are involved in stimulating specific immune response.

24
Q

What are lysozymes ?

A

The digestive enzyme found in lysosomes as well as tears and mucus
They damage bacterial cells walls

25
Q

Outline how to prepare a blood smear

A

Smear a drop of blood onto a slide using a spreader at 45•
Add leishman stain then a buffer
Rinse

26
Q

Name the two types of specific immune response.

A

Cell mediated
Humoral

27
Q

Outline the process of cell mediated response.

A

*Complementary Tʜ cells bind to the foreign antigen on the APC
*Cell signalling via secretion of interleukins stimulates :
*a) Clonal expansion of Tʜ cells to become memory cells (humoral response)
*b) Clonal expansion of cytotoxic T cells to secrete the enzyme perforin to destroy infected cells.

28
Q

Outline the process of humoral response.

A

*Complementary Tʜ lymphocytes bind to foreign antigen on APC cells
*Cytokines released by Th lymphocytes that stimulate Clonal expansion of complementary B lymphocytes
*B lymphocytes differentiate into plasma cells
*Plasma cells secrete antibodies with complementary variable region to antigen

29
Q

Describe the structure and function of B and T lymphocytes.

A

Both have many specific receptors on surface
B cells differentiate into plasma cells and produce antibodies
There are 3 types of T cell:
T helpers secrete cytokines (stimulate cells to move towards site of injury/disease)
T killers secrete perforin (creates pore in target cells)
T regulators suppress the other two cells to prevent autoimmune disease

30
Q

What is an antibody ? Describe / draw it’s structure.

A

They are proteins secreted by plasma cells
Quaternary structure : 2 ‘light chains’ held by disulphide bridges to two ‘heavy chains’
The binding sites of variable regions of the light chains have specific tertiary structure to an antigen
The rest of the molecule is known as the constant region.

31
Q

How do antibodies lead to the destruction of a pathogen ?

A

*Agglutinins form antigen-antibody complexes to enhance phagocytosis by making pathogens clump together
*Opsonin antibodies can attach to bacteria making them readily identifiable to phagocytes.
Antitoxins make toxins insoluble.

32
Q

What are memory cells ?

A

Specialised Tʜ / B cells produced via the primary immune response
Remain in low levels in the blood
Can divide very rapidly by mitosis if organism encounters the same pathogen again

33
Q

Contrast the primary and secondary immune response

A

Secondary response has:
A faster rate of antibody production
Shorter time lag between exposure and antibody production
Higher conc or antibodies
Antibody remain higher after secondary response
Pathogen typically destroyed before symptoms occur.

34
Q

Contrast and compare passive and active immunity.

A

•Passive has no memory cells while active does
•Passive is immediate while active requires time for synthesis
•Passive has antibodies from external source and active has lymphocytes produce antibodies
•Passive requires no direct contact with pathogen while active requires contact.

35
Q

Give examples of passive and active immunity.

A

Passive natural - antibodies in breast milk
Passive artificial - blood transfusion with antibodies
Active natural - humoral response to infection
Active artificial - vaccination.

36
Q

Define autoimmune diseases, give examples.

A

When the immune system produces antibodies that target its own tissues
Eg. HIV and arthritis.

37
Q

Explain the principles of vaccination.

A

•Vaccine contains dead/inactive form of pathogen
•This triggers primary immune response
•B lymphocytes then become memory cells, allowing for the secondary response to be rapid
•Upon reinfection the pathogen can now be destroyed before symptoms.

38
Q

Define endemic and epidemic ?

A

Endemic : disease occurs routinely in an area
Epidemic : temporary rapid increase in disease in an area

39
Q

What role does vaccination play in preventing epidemics ?

A

•Vaccination of a high percentage of a population reduces the available carriers of a pathogen, resulting in herd immunity

40
Q

List some possible natural sources of medicine.

A

•Microorganisms
•Fungi
•Plants
•This is an important reason to maintain biodiversity as it means new sources may be discovered.

41
Q

What is personalised medicine and synthetic biology ?

A

Personalised medicine : observing the genome of an individual to predict their response to disease, and the best prescription
Synthetic biology : engineering that targets biological processes.

42
Q

What are the benefits of using antibiotics to treat bacterial infections? How do they do this?

A

Effectively reduce the population of bacteria by :
Preventing protein / nucleic acid synthesis
Preventing formation of peptidoglycan cell walls.

43
Q

What are the risks of using antibiotics to treat bacterial infections ?

A

•Overuse of antibiotics increases selection pressure for resistant strains of bacteria
Antibiotic resistant infections are more difficult to treat.

44
Q

What do mature B lymphocytes do ?

A

Produce specific antibodies (proteins) to neutralise a specific antigen.

45
Q

What is clonal selection of T/B lymphocytes ?

A

It is when the complementary antigen (from pathogen) and the receptor on the T/B cell’s surface bind

46
Q

What causes clonal expansion ?

A

When a T cell becomes activated (whether by contact with antigen or interleukins) it undergoes mitosis rapidly in order to make more useful cells to destroy the pathogen
The process of rapid division is clonal expansion.

OCR A Level Biology (24 decks)

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