Ib Biology Sl Assessment Statements 6.3

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6.3.4
Leucocytes are white blood cells. Phagocytes are found in the blood and ingest pathogens. One is called Macrophage. They change their cellular shape to surround an invader and take it through the process of phagocytosis. It recognizes if the cell is ‘self’ or ‘not self’, by the protein make-up of the cell. The ‘not self’ cells are engulfed and then the enzymes within the phagocytes called lysosomes then digest the pathogens. Phagocytes can ingest pathogens in the blood but also within body tissue as they can pass through the pores of capillaries and into these tissues. 6.3.6

Antibodies are protein molecules which are produced in response to a specific pathogen. Each antibody is different. It’s a Y shaped protein that attaches to the antigen on a (bacteria) cell. Steps of immune response and creation of antibodies;

1.A specific antigen type is identified
2.A specific B lymphocyte is identified that can produce an antibody which will bind to the antigen (proteins on the pathogen) 3.The B lymphocytes and several identical B lymphocytes clone themselves via mitosis to rapidly increase the number of B lymphocytes. 4.The newly formed army begins antibody production

5.Newly released antibodies circulate in the bloodstream and eventually find their antigen match. 6.Using various mechanisms, the antibodies eliminate the pathogen 7.Some o the cloned anti-body producing lymphocytes remain in the bloodstream and give immunity from a second infection of the same pathogen. They are called memory cells.

6.3.7
HIV – human immune deficiency virus.
The HIV virus (which causes AIDS) destroys a type of lymphocyte which has a vital role in antibody production. Over the years this results in a reduced amount of active lymphocytes. Therefore, less antibodies are produced which makes the body very vulnerable to pathogens. A pathogen that could easily be controlled by the body in a healthy individual can cause serious consequences and eventually lead to death for...
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