5.1: Defence Mechanisms

Question 1

Main Defence Mechanisms

Answer 1

• Physical barriers (Mucus, Skin, Earwax)
• General and immediate (Skin forming to prevent infection) - Scabs
• Specific and long-lasting, involve lymphocytes

Cell-Mediated responses = T-Lymphocytes
Humoral responses = B-Lymphocytes

Question 2

How do Lymphocytes distinguish the body’s own cells

Answer 2

Each cell (self or non-self) have specific proteins that identify it. These molecules can be a variety of types due to Proteins having an enormous variety and a specific Tertiary Structure.

Question 3

What type of things do protein molecules allow the immune system to identify

Answer 3

Pathogens - E.G, HIV

Non-Self material - such as cells from other organisms of the same species

Toxins - Such as those produced by certain pathogens like Cholera bacterium

Abnormal body cells - such as Cancer Cells

Question 4

How do Lymphocytes recognise cells belonging to the body

Answer 4

There are over 10 million different lymphocytes present at any time. Each capable of identifying different chemical shape.

In the fetus, these lymphocytes constantly collide with other cells

Lymphocytes will constantly collide with the bodys own material. If they have receptors which fit to the own body’s cells then they are killed

The only remaining lymphocytes are those that fit foreign material, and therefore only respond to foreign material.

Question 5

What response are each lymphocyte involved in

Answer 5

T lymphocytes - Cell-Mediated Response

B lymphocytes - Humoral Response

Question 6

Difference between a specific and non-specific response

Answer 6

Specific - the response is immediate and the same for all pathogens

Non-specific - the response is sower and specific to each pathogen