Cell recognition

Question 1

Our bodies have several defence mechanisms against pathogens. These include:

non specific immune response Preventing the entry of pathogens by a variety of physical and chemical defences, such as

Answer 1

as the skin, mucous membranes, tears (containing the enzyme lysozyme, which destroys bacteria by breaking down cell wall) and saliva

blood clot seals wound

phagocytosis

antimicrobial proteins interferon prevents viral replication

Question 2

Inflammation (swelling and heating) of the region invaded by the pathogen, a process known as a ………

and how does it help

Answer 2

non-specific inflammatory response

more white blood cells can get to an area to destroy microbes

Question 3

Recognising ‘foreign’ cells and targeting any pathogenic cells, a process known as a

Answer 3

specific immune response

Question 4

This ability to recognise ‘foreign’ cells is made possible by specific molecules found on the surface of cells ……………. that enable them to be identified by the ………….

Answer 4

Antigens
body

Question 5

This ability to recognise ‘foreign’ cells is made possible by specific molecules found on the surface of cells (and viral particles) that enable them to be identified by the body

These molecules are usually proteins
They are often ……….. that are part of the phospholipid bilayer, such as ………..

However, …………can also act as similar markers

Answer 5

proteins
glycoproteins

glycolipids

Question 6

They allow the body to recognise its own cells (………..) and foreign cells (…………’)

Answer 6

self

non-self’)

Question 7

These surface proteins are found on (and enable the body to recognise) the following:

Answer 7

Pathogenic cells

Abnormal body cells, such as cancerous or pathogen-infected cells

Toxins (these are chemical rather than cellular, in nature)

Cells from other individuals from the same species (in order for organ transplants to occur successfully the body must not recognise the cells and tissues of the donated organ as foreign, so that no immune response occurs)

Question 8

The surface molecules used by the body to identify cells, viral particles and toxins are known as

Answer 8

antigens

Question 9

An example of the importance of antigens in defending against pathogens:

White blood cells known as phagocytes have surface proteins that act as receptors and bind to the proteins (antigens) on the surface of pathogens

This enables pathogens to be ………….

The antigens that were found on the pathogen can then be presented on the surface of the phagocyte (now an ………………. cell

This is then used to recruit other cells of the immune system, leading to a ……..

Answer 9

engulfed and digested

antigen-presenting cell

specific immune response

Question 10

Pathogens can cause damage to a host in a number of ways. For example, they can

Answer 10

damage host tissue/cells and produce toxins.

bacteria produce toxins

viruses divide inside cell and eventually burst it

Question 11

A non specific response histamines what do they do

Answer 11

Histamines make blood vessels dilate, causing an increase in temperature which stop the pathogen reproducing.

Histamines cause blood vessels to become more permeable, so plasma is forced out producing swelling.

Cytokines attract phagocytes, which destroy pathogens in phagocytosis.