responding antigen

Question 1

Define an antigen.

Answer 1

An antigen is a unique molecule or part of a molecule that can initiate an immune response.

Question 2

Define a pathogen.

Answer 2

A pathogen is a disease-causing agent

Question 3

How is non-cellular defined?

Answer 3

They require a host cell as they cannot reproduce outside a host cell
No metabolic cellular processes (whilst they have DNA or RNA they have no organelles to generate energy or proteins)
Not made of cells

Question 4

What are prions?

Answer 4

Prions are abnormal infectious proteins.

Question 5

What is a virus composed of?

Answer 5

Genetic material (DNA or RNA) and protein coat (capsid)

Question 6

What are examples of chemical barriers and how do they prevent the entry of a pathogen in plants?

Answer 6

Secretion of enzymes
Secretion of toxins e.g. Phytoalexins which are antimicrobial compounds produced by damaged plant cells
Odour chemicals e.g. peppermint that act as natural pesticides
Coffee plants use caffeine to ward off insects
When a plant is wounded resin is secreted which closes the wound over to prevent pathogen entry.

Question 7

What are examples of physical barriers and how do they prevent the entry of a pathogen in plants?

Answer 7

Intact bark and thick waxy cuticles provide a protective coat through which pathogens cannot enter.
Hair on the leaves and surrounding the stomata prevent the entry of pathogens.
Galls are abnormal swellings at the infection site which limit the movement of the pathogen by trapping it in this area.
Stomata are often sunken within the leaf to prevent pathogens entering.

Question 8

What is an example of a microbiota barrier in plants?

Answer 8

Rhizosphere is the area around a plant root that is inhabited by a unique population of microorganisms and is influenced by the chemicals released from plant roots, this acts as a microbiota barrier in plants as the naturally occurring bacteria outcompete the pathogenic bacteria in the soil

Question 9

What is an example of a microbiota barrier in humans?

Answer 9

Many microbes live in a symbiotic relationship with humans these microbes outcompete pathogenic bacteria preventing them establishing colonies in the human body e.g. on the skin or in the alimentary canal.

Question 10

What are examples of chemical barriers and how do they prevent the entry of a pathogen in humans?

Answer 10

weat secretes both salt and fatty acids which are bacterial inhibitors and prevent pathogen infection.
Saliva and tears secrete lysozymes which are enzymes that break bacterial cell walls, so bacterial cells burst due to osmosis.
The lungs secrete a mucus from goblet cells that helps trap dirt and pathogenic particles, this mucus is then removed via the cilia that pass the mucus up and out of the lungs and nose.
The stomach secretes a strong hydrochloric acid which kills the majority of pathogens that enter via the digestive system.

Question 11

What are examples of physical barriers and how do they prevent the entry of a pathogen in humans?

Answer 11

Intact skin prevents the entry of pathogens
Hairs in our ears and nose trap foreign particles
Ear wax traps foreign particles

Question 12

What is a chemical barrier?

Answer 12

some type of secreted chemical that helps prevent the entry of a pathogene

Question 13

what is a virus composed of?

Answer 13

a protein coat ( capsid) and genetic material( DNA or RNA)

Question 14

how do bacteria cause disease

Answer 14

Release toxins and rapidly reproduce via binary fission (causing an increase in toxin concentration)

Question 15

What is a physical barrier?

Answer 15

physical structures that prevent the pathogen from entering

Question 16

What are examples of physical barriers and how do they prevent the entry of a pathogen in humans?

Answer 16

Intact skin prevents the entry of pathogens
Hairs in our ears and nose trap foreign particles
Ear wax traps foreign particles

Question 17

What are the roles of the lymphatics sytem in the immune response?

Answer 17

Transport system for phagocytes/T and B cells/natural killer cells/eosinophils
Site of antigen recognition by T and B cells (in lymph node).

Question 18

What are examples of lymphocytes?

Answer 18

T cells, B cells, Natural Killer cells

Question 19

What is the role of the thymus?

Answer 19

Maturation of T lymphocytes

Question 20

What is the function of the bone marrow?

Answer 20

Produce white blood cells and maturation of B lymphocytes

Question 21

What is the purpose of valves in the lymphatic system?

Answer 21

Keep lymph flowing in one direction (unidirectional)

Question 22

What is the relationship between plasma, tissue fluid and lymph?

Answer 22

Plasma is the fluid component of blood in the circulatory system, when this leaks out of capillaries it is referred to as tissue fluid, 90% of this tissue fluid is reabsorbed by the capillaries and 10% enters the lymph vessel where it is now known as lymph. Lymph fluid returns back to the blood via the lymphatic system.

Question 23

What are the characteristics of innate immunity?

Answer 23

Acts broadly against actions of pathogens
Reaction is same for ALL pathogen
Has no ‘memory’ of previous pathogen
Response level is the same for all non-self material encountered
Response is immediate

Question 24

What is the role of a phagocyte?

Answer 24

Recognise, engulf and digest foreign material, such as pathogens, through phagocytosis.

Question 25

Give 3 examples of phagocytes.

Answer 25

Neutrophil, macrophage, dendritic cell

Question 26

List the cells of the innate immune response

Answer 26

Phagocytes (neutrophils, macrophages, dendritic cells), mast cells, eosinophils, natural killer cells

Question 27

Describe two roles of a phagocyte

Answer 27

Antigen presenting cell (macrophage and dendritic) this means that it moves from the site of infection to the lymph node to present the non-self antigen of the engulfed pathogen on its MHCII marker to initiate the adaptive immune response. Phagocytosis this means that it will recognise, engulf and digest foreign material, such as pathogens

Question 28

What is the role of a complement proteins?

Answer 28

Chemotaxis. This means that the complement proteins gather near the (context) pathogen and attract phagocytes to it making phagocytosis easier.(1) Opsonisation. This means that they attach to non-self antigen on (context) pathogen making them easier to identify and making phagocytosis easier.(1) Lyse plasma membrane of (context) bacteria pathogen so it will die.(1) Promote inflammation. This means that it will will help eliminate (context) pathogen.(1)

Question 29

What is the role of a cytokine?

Answer 29

These proteins act as messengers between cells of the immune system, as well as other body systems e.g. nervous system

Question 30

What is the role of interferon?

Answer 30

Secreted by cells when they are virus infected, this warns other nearby cells and makes them more virus resistant

Question 31

What is the role of eosinophils?

Answer 31

They will target extracellular pathogens that are too large to be engulfed by the phagocytes eg. parasites

Question 32

What is the role of a natural killer cell?

Answer 32

They recognise non-self antigen on MHCI markers and release cytotoxic chemicals which destroy the virally infected cell or cancerous/tomour cell

Question 33

Which cells have MHCI markers?

Answer 33

All nucleated cells of the body

Question 34

Which cells have MHCII markers?

Answer 34

Macrophage and dendritic

Question 35

Describe what occurs to cause swelling in the inflammation process

Answer 35

An increase in permeability of blood vessels occurs, this means that more plasma leaks into the tissue, increasing tissue fluid and causing swelling (and also trapping the pathogen in the area)

Question 36

Describe what occurs to cause redness in the inflammation process

Answer 36

Vasodilation occurs this means that more blood goes to the site of infection causing it to become red

Question 37

Describe what occurs to cause heat in the inflammation process

Answer 37

Vasodilation occurs this means that more blood goes to the site of infection causing it to heat up

Question 38

Describe what occurs to cause pain in the inflammation process

Answer 38

An increase in permeability of blood vessels occurs, this means that more plasma leaks into the tissue, increasing tissue fluid and causing it to press on nerve endings

Question 39

What pathogens does the humoral response target? Which cells are involved?

Answer 39

Extracellular pathogens, B lymphocytes

Question 40

How do antibodies work?

Answer 40

Immobilising pathogens- sticking to non-self antigens of pathogen prevent these binding to a receptor Agglutination of pathogens - clumping together Flagging of pathogens for phagocytosis Activate complement proteins

Question 41

What is clonal selection? And name the location where it occurs.

Answer 41

The specific and complementary T helper cell is selected when an antigen presenting cell presents a non-self antigen to it. This T helper cell secretes cytokines to active a B cell. This B cell is then selected as it recieves this cytokine and it’s membrane bound antibodies bind to the non-self antigen presented by an antigen presenting cell. This occurs in the lymph node

Question 42

What is clonal differentiation?

Answer 42

B lymphocytes divide to become either Plasma cells or B memory cells

Question 43

What is clonal expansion?

Answer 43

When the B cell has attached to the antigen it then rapidly divides by mitosis forming plasma cells and B memory cells

Question 44

What is the function of a plasma cell?

Answer 44

Plasma cells produce specific and complementary free-floating antibodies

Question 45

What is the function of a B memory cell?

Answer 45

Remain in circulation after the pathogen has been dealt with and when the same pathogen is encountered again, they divide by mitosis more rapidly forming Plasma cells and more B memory cells. This leads to a higher concentration of anitbodies.

Question 46

How does the secondary immune response differ from the primary immune response?

Answer 46

The secondary immune response has a more RAPID production in the secondary response, and a HIGHER CONCENTRATION of antibodies

Question 47

What is the function of a cytotoxic T cell?

Answer 47

Recognise non-self antigens on MHCI markers of infected body cell (particularly with a virus), tumour cells or foreign tissues and produce cytotoxic chemicals (perforins) that destroy the target cell by causing holes in the plasma membrane.

Question 48

Compare a cytotoxic T cell and a natural killer cell.

Answer 48

A cytotoxic T cell is a part of the adaptive immune response whereas a natural killer cell is a part of the innate immune response. A cytotoxic T cell forms T memory cells/immunological memory whereas a natural killer cell does not.

Question 49

Define disease

Answer 49

Physical or mental disturbance involving symptoms, dysfunction or tissue damage