IMMUNITY

Question 1

What is phagocytosis?

Answer 1

The use of phagocytes, a type of white blood cell in the blood, to neutralize any pathogens in the body

In the presence of a pathogen, the phagocytes extends its cytoplasm, forming pseudopods.
These pseudopods surround the pathogen, and trap it in a vacuole
Digestive enzymes are secreted into the vacuole, breaking down the pathogen, neutralizing it.

Question 2

What does production of antibodies involve?

Answer 2

Lymphocytes are another type of white blood cell, that create chemicals called antibodies.
Pathogens have antigens on their surface, that act as markers for the antibodies to recognise.
The antibodies are used to destroy the pathogen by:
1. Sticking bacteria together for easier digestion by phagocytes
2. Labelling pathogens for easier location by phagocytes
3. Bursting open bacterial cells
4. Neutralizing toxins produced by pathogens
This is a primary immune response, because there was no prior infection

Question 3

What are memory cells?

Answer 3

Some lymphocytes produce memory cells in the presence of a pathogen, rather than making antibodies.
In the event of a re-infection of the same pathogen, these memory cells reproduce, and antibodies are produced to kill the pathogen quickly.
This is what makes people immune to certain diseases, and is a secondary immune response, because there was a prior infection

Question 4

What does vaccination involve?

Answer 4

1. A dead/weakened form of a pathogen (e.g tuberculosis), is injected into the bloodstream.
   Although this poses no threat, lymphocytes still recognise the antigens and memory cells are produced
   Now, in the event of a real infection, those memory cells will produce lymphocytes and antibodies, and a secondary immune response occurs without actually getting infected prior.