Biology Unit 1

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Phagocytes engulf pathogens, a phagocyte is a type of white blood cell, it recognizes the antigens on a pathogen. The cytoplasm of the phagocyte moves around the pathogen and engulfs it, it is now contained in a phagocytic vacuole. The lysosome in the phagocyte fuses with the phagocytic vacuole and begins to break down the pathogen. The phagocyte then presents the antigens of the pathogen to other immune system cells and alerts them - T Cells. T-Cell is a type of white blood cell, it has proteins on its surface which bind to the anitgens presented to it by the phagocyte - this then activates the T Cell which works in 2 different ways: T-Cells can attach directly to antigens on a pathogen and kill the cell and some release a substance which activates B-Cells. B-Cells are covered with antibodies - proteins that bind to antigens and form an antigen-antibody complex. When a complementaty shaped antigen meets the antibody on the surface of a B Cell it binds to it, this together with substances released from the T cell activates the B Cell. The B Cell then divides into plasma cells. plasma cells are identical clones of b cells, they secrete lots of the antibody specific to the antigen, antibody functions include coating the pathogen making it easier for the phagocyte to engulf, neutralizing toxins released by the pathogen and coating the pathogen to prevent it from entering host cells. 

Primary and Secondary Response - 

Primary Respone: a pathogen enters the body for the first time, the immune system response is triggered, this is known as the primary response, the primary response is slow because there aren't many B Cells produced which have the antibody needed to bind to the antigen which is infecting the body. after time, enough of the antibody will be secreted to overcome the infection but in the meantime you will suffer symptoms of the disease. after being exposed to the antigen first time round, your body produces memory T AND B Cells, memory T-Cells remember the specific antigen and will recognize it next time and memory B Cells remember the specific antibody needed to bind to the antigen. the person is now immune and their secondary response will be much quicker if the person was to be infected again. 

Secondary response - when the same pathogen/antigen enters your body again, the secondary response is activated, this response is much faster and much stronger. Memory T Cells divide into the right type of T cell needed to kill the cell carrying the antigen and memory B Cells divide into plasma cells to secrete the specific antibody needed to bind to the antigen, this response will often rid you of the disease before you show any symptoms. 

Vaccinations and Antibodies in Medicine

You become immune from the disease without suffering any symptoms, vaccinations always contain a dead or weakened pathogen attached to them, meaning the pathogen cannot cause infection within your body but your body will still


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