Lesson 3: Defence against disease

Question 1

What are pathogens?

Answer 1

organisms that cause disease

Question 2

What are the different types of pathogens?

Answer 2

• bacteria
• fungi
• protists
• viruses
• prions

Question 3

How is bacteria harmful?

Answer 3

Produce toxins that damage body cells.

Question 4

How is fungi harmful?

Answer 4

Digest living cells to destroy them. Some also produce toxins.

Question 5

How is protist harmful?

Answer 5

Take over cells and break them open.

Question 6

How are viruses harmful?

Answer 6

Use host cells to replicate before bursting out and destroying cells.

Question 7

How are prions harmful?

Answer 7

causes degeneration of the nervous system

Question 8

What color is gram positive bacteria after gram staining?

Answer 8

blue-purple

Question 9

What color is gram negative bacteria after gram staining?

Answer 9

red

Question 10

What are the two main defence mechanisms against pathogens?

Answer 10

non-specific and specific

Question 11

What is non-specific defence?

Answer 11

response is the same for all pathogens

Question 12

What is specific defence?

Answer 12

response is specific to each pathogen

Question 13

What are some physical and chemical barriers against pathogens?

Answer 13

Skin - physical barrier but also produces sebum which inhibits growth of pathogens

Mucous membranes - traps pathogens and uses lysozymes to destroy them.

Skin flora - large population of natural and healthy bacteria that outcompete pathogens for surface area.

Question 14

How does blood clot?

Answer 14

• Damaged cells release chemicals that stimulate platelets to adhere to damaged area.
• damaged cells and platelets release chemicals called clotting factors that convert prothrombin (clotting protein) into thrombin.
• Thrombin is an active enzyme that catalyses the conversion of soluble fibrinogen (another clotting protein) into insoluble fibrin which is a fibrous protein that forms a mesh-like network to stabilize the platelet plug.
• More and more cellular debris becomes trapped in the fibrin mesh until stable clot is formed.

Question 15

What are the differences between innate and adaptive immune systems?

Answer 15

Innate:
* present from birth
* provides rapid
* non-specific defences against pathogens.
* Mediated by phagocytes.
Adaptive:
* Develops during our lives
* slower
* specific
* mediated by lymphocytes

Question 16

What is the role of phagocytes?

Answer 16

engulf and destroy pathogens

Question 17

What are the two main types of phagocytes?

Answer 17

neutrophils and macrophages

Question 18

What are the stages of phagocytosis?

Answer 18

The pathogen releases chemicals that attract a phagocyte.
The phagocyte recognises the pathogen’s antigens as non-self. This causes the phagocyte to bind to the pathogen.
The phagocyte engulfs the pathogen.
The pathogen is now contained within a vacuole known as a ‘phagosome’.
The lysosome, containing lysozymes, fuses with the phagosome to form a phagolysosome.
The phagocyte presents the pathogen’s antigens on its surface to activate other cells in the immune system. The phagocyte is then referred to as an antigen-presenting cell (APC).

Question 19

When is the adaptive immune system needed?

Answer 19

Innate immune system is unable to control an infection.

Question 20

What are the two main types of lymphocytes?

Answer 20

B lymphocytes
T lymphocytes

Question 21

Where do B lymphocytes mature?

Answer 21

bone marrow

Question 22

Where do T lymphocytes mature?

Answer 22

thymus gland

Question 23

What system plays a role in the immune response of the body?

Answer 23

lymphatic system

Question 24

Where can you usually find lymphocytes after maturation?

Answer 24

Some of them remain in circulation while others are concentrated in the secondary lymphoid organs

Question 25

What immunity are T lymphocytes involved in?

Answer 25

cell-mediated immunity

Question 26

What response are B lymphocytes involved in?

Answer 26

humoral response

Question 27

What are the types of T cells/lymphocytes?

Answer 27

T helper cells T killer cells T regulator cells T memory cells

Question 28

What are the functions of T killer cells?

Answer 28

kill abnormal and foreign cells by producing a protein known as perforin which makes holes in the cell-surface membrane, causing it to become freely permeable and causing cell death.

Question 29

What are the function(s) of T regulator cells?

Answer 29

suppress the immune system after pathogens have been destroyed

Question 30

What are the function(s) of T memory cells?

Answer 30

provide a rapid response if the body is re-infected by the same pathogen.

Question 31

What are antibodies?

Answer 31

Y-shaped proteins that bind to a specific antigen that has triggered an immune response.

Question 32

What is the structure of antibodies?

Answer 32

2 heavy chains bonded to 2 light chains through disulphide bridges

Question 33

What mechanism do antibodies bind to antigens with?

Answer 33

lock and key

Question 34

What is the binding site on antibodies called?

Answer 34

variable region

Question 35

What is the function of hinge regions on antibodies?

Answer 35

allows flexibility, meaning two antigens can bind at once.

Question 36

What is formed when an antibody binds to an antigen?

Answer 36

antigen-antibody complex

Question 37

What are the 3 ways antibodies can defend against pathogens?

Answer 37

opsonin agglutinins anti-toxins

Question 38

What is the opsonins method?

Answer 38

bind to and ‘tag’ pathogens, making them recognisable to phagocytes.

Question 39

What is the agglutinins method?

Answer 39

causes pathogens to clump together

Question 40

What is the anti-toxins method?

Answer 40

binds to toxins and making them harmless.

Question 41

Which response requires the production of antibodies, humoral or cellular?

Answer 41

humoral

Question 42

Stages of humoral response

Answer 42

* Helper T-cells are stimulated by APCs and release interleukins. * Colonal selection - stimulates selected B cell to clone by mitosis * Clonal expansion - clones differentiate into plasma cells or memory cells * Primary immune response - plasma cells produce antibodies * Secondary immune response - memory cells circulate the blood and is ready to divide if body encounters the same pathogen.

Question 43

How is HIV transmitted?

Answer 43

* unprotected sex * blood transfusions * breastfeeding

Question 44

What are the effects of HIV?

Answer 44

t-helper cells are killed which is used to activate B-cells which produce antibodies, therefore victims develop a weak immune system (AIDS stage) and die due to inability to fight off diseases.

Question 45

What is one way of determining the progression of HIV?

Answer 45

measure the helper T-cell count

Question 46

What are antibiotics?

Answer 46

drugs used to treat bacterial infections.

Question 47

What are the two types of antibiotics?

Answer 47

Bactericidal Bacteriostatic

Question 48

How do bacteriostatic antibiotics work?

Answer 48

slow the growth or reproduction of bacteria.

Question 49

How do bactericidal antibiotics work?

Answer 49

kill bacterial cells

Question 50

What can antibiotics target in bacteria?

Answer 50

protein synthesis membrane integrity cell wall

Question 51

What is antibiotic resistance?

Answer 51

bacteria with resistance to antibiotics due to genetic mutation

Question 52

What are the steps of achieving antibiotic resistance?

Answer 52

* Genetic mutations occur, making some bacteria resistant to an antibiotic. * When an infection is treated with antibiotics, resistant bacteria are able to survive. * Resistant bacteria reproduce, passing on the allele for antibiotic resistance to their offspring.

Question 53

What is the issue with antibiotic resistance?

Answer 53

resistance is developing faster than new antibiotics

Question 54

How to prevent antibiotic resistance?

Answer 54

* Practise good hygiene * Take antibiotics only when needed * Make sure to complete the full course of antibiotics.

Question 55

What are zoonotic diseases?

Answer 55

disease that can spread from non-human vertebrate animals to humans.

Question 56

What are spillover events?

Answer 56

when pathogens which are found in other animals cross to humans.

Question 57

How are the chances of spillover events increased?

Answer 57

Consumption of their meat Poaching Deforestation

Question 58

How do vaccines work?

Answer 58

may contain any of the following: * Dead or inactivated pathogens. * Attenuated (weakened) pathogen strains. * A harmless version of a toxin. * Isolated antigens from a pathogen. * Genetically engineered antigens. This stimulates the primary immune response to produce antibodies against the pathogen. Memory cells, capable of recognising these antigens, are produced.

Question 59

What is the difference in immune response between the first and second vaccination?

Answer 59

second immune response is larger and stronger than first

Question 60

What is herd immunity?

Answer 60

when a significant number of people in the population have been vaccinated, giving protection to those that do not have immunity.

Question 61

What factors need to be considered when evaluating data related to the COVID-19 pandemic?

Answer 61

* Data sources * Data types * Data collection * Data representation * Data limitation

Question 62

How are T helper cells activated?

Answer 62

when it binds to a complementary antigen

Question 63

What paths can a T-helper cell take after activation?

Answer 63

* More helper T-cells are produced * Produces interleukins which activates the B-cells specific to the same antigen * Produces interleukins which activates killer T-cells specific to the same antigen