M24. Fighting Disease p2

Question 1

What are primary defences?

Answer 1

Defences that attempt to prevent pathogens from entering the body

Question 2

What is an immune response?

Answer 2

The specific response to a pathogen, which involves the action of lymphocytes and the production of antibodies.

Question 3

What is the main primary defence?

Answer 3

the skin, specifically the outer layer of the skin- the epidermis

Question 4

What does the epidermis layer of skin mainly consist of

Answer 4

layers of cells, most of which are called keratinocytes, which are produced by mitosis at the base of the epidermis

Question 5

Why are the airways, lungs and digestive a potential area for infection?

Answer 5

As nutrients and oxygen must enter the blood system, so they must be allowed past the primary defence systems and therefore have the potential of bringing infection into the body.

Question 6

How are the lungs, airways and digestive system protected from infection?

Answer 6

by being covered in mucus- membranes (goblet cells) which are aided by ciliated epithelium.

Question 7

Why are most pathogens killed in the digestive system?

Answer 7

As it has an pH of 1-2 which denatures the pathogen’s enzymes.

Question 8

Give some examples of where mucous membranes are found

Answer 8

gut
genitals 
anus
ears
nose

Question 9

Name 3 other primary defences

Answer 9

The eyes are protected by antibodies in tear fluid
The ear canal is lined with wax, which traps pathogens
The vagina is protected by maintaining a relatively high acidic conditions

Question 10

What is the role of non-specific phagocytes

Answer 10

to kill pathogens that have got past the primary defences before they begin to reproduce

Question 11

What are the two types of phagocytes

Answer 11

neutrophils

macrophages

Question 12

Describe a neutrophil
how common
how is it recognised
where is it made
where is it found
how long does it live
how is it effective

Answer 12

• Most common phagocyte
• Recognised by its lobed nucleus
• manufactured in bone marrow
• found in blood, tissue fluid, epithelial surfaces eg lungs
• short lived, but released in large numbers

Question 13

Describe a macrophage
how big
where are they produced
how do they travel round the body
where do they develop
what role do they play

Answer 13

• larger than neutrophil
• producsed in bone marrow
• travel in the blood as a monocyte
• monocytes develop into macrophages in the body organs, particularly the lymph nodes
• play a role in specific responses to invading pathogens

Question 14

How do phagocytes work?

Answer 14

• pathogen attached to phagocyte by antibody and surface receptors
• pathogen is engulfed by infolding of phagocyte membrane
• lysosomes release lysins into phagosome
• harmless end product of digestion are absorbed

Question 15

How are pathogens recognised?

Answer 15

As a foreigner by the chemical markers on its outer membrane called antigens.

Question 16

What helps the process of phagocytes receptors binding to foreign antibodies

Answer 16

opsonins

Question 17

What is the vacuole called that phagocytes engulf pathogens in?

Answer 17

phagosome

Question 18

How does dead neutrophils removed?

Answer 18

they collect in the area of infection and form pus.

Question 19

What role does histamine play in defence against pathogens?

Answer 19

It is released from infected cells and attracts neutrophils to the area, and causes a response that makes capillaries more leaky so more fluid leaves the capillaries in the area of infection

Question 20

Why is it important that histamines produce a response that makes the capillaries more leaky?

Answer 20

So that more tissue fluid passes into the lymphatic system where macrophages are sat waiting to engulf the pathogens.

Question 21

What is an immune response?

Answer 21

the activation of lymphocytes in the blood to help fight disease.

Question 22

What is an antigen?

Answer 22

molecules that stimulate an immune response

Question 23

What is an antibodie?

Answer 23

protein molecules that can identify and neutralise antigens.

Question 24

What is specificity in terms of antibodies and antigens

Answer 24

an antibody is specific to a particular antigen because of the shape of the variable region. Each type of antibody has a differently shaped variable region

Question 25

Describe what an antigen usually looks like

Answer 25

a larger molecule with a specific shape (almost any molecule could act as an antigen)
They are usually proteins or glycoproteins in or on the plasma membrane (cell surface membrane)

Question 26

Why dont our own antigens stimulate a response?

Answer 26

As they are recognised by the immune system.

Question 27

What are antigen molecules produced by?

Answer 27

the lymphocytes

Question 28

What are antibodies often referred to as?

Answer 28

immunoglobins, large proteins

Question 29

How do antibodies work?

Answer 29

They attach to antigens and render them harmless

Question 30

Describe the structure of an antibody briefly

Answer 30

Y shaped molecule that have 2 distinct regions- variable and constant

Question 31

Describe in detail, the structure of an antibody

Answer 31

• 4 polypeptide chains held together with disulphide bridges
• a constant region which is the same in all antibodies, that enables the antibody to attach to phagocytic cells and helps in the process of phagocytosis
• a variable region which has a specific shape and differentiates the different antibodies.
• hinge regions, which allows more flexibility, allowing the branches to move further apart to allow the antibody to attach to more than one antigen.

Question 32

Which region of an antibody has light and heavy polypeptide chains

Answer 32

light; variable

heavy; constant

Question 33

What is neutralisation and what is it an example of?

Answer 33

Where the antibody binds to the binding site of a pathogen to prevent the pathogen from binding with a host cell.
Its an example of how pathogens act defensively.

Question 34

What is aggulation?

Answer 34

a large antibody binds many pathogens together, then the large group of pathogens is too large to enter a host cell.

Question 35

When is aggulation used rather than neutralisation?

Answer 35

When the antibodies are larger.

Question 36

What is the primary immune response?

Answer 36

The response of the immune system when it first meets a new invader, but this can take a few days to build up enough antibodies.

Question 37

What happens once the infection has been dealt with ?

Answer 37

The number of antibodies decreases rapidly

Question 38

What is the secondary immune response.

Answer 38

The time the production starts is much quicker and they are made much more quickly so the concentration of antibodies rises sooner and reaches a much higher concentration.