Photo AI
Question 22 (6 marks) (a) Describe how phagocytes help protect against pathogens - HSC - SSCE Biology - Question 22 - 2023 - Paper 1
Question 22
Question 22 (6 marks) (a) Describe how phagocytes help protect against pathogens. (b) Explain how antibodies are produced in response to the entry of a pathogen.
Worked Solution & Example Answer:Question 22 (6 marks) (a) Describe how phagocytes help protect against pathogens - HSC - SSCE Biology - Question 22 - 2023 - Paper 1
Step 1
Describe how phagocytes help protect against pathogens.
Answer
Phagocytes are a type of white blood cell that play a crucial role in the immune response. They help protect against pathogens primarily through a process known as phagocytosis. When a phagocyte encounters a pathogen, it engulfs the pathogen by surrounding it with its cell membrane. This process effectively isolates the pathogen from the rest of the body.
Once the pathogen is engulfed, the phagocyte internalizes it into a compartment called a phagosome. The phagosome then fuses with lysosomes, which contain digestive enzymes that break down the pathogen into harmless particles. This not only eliminates the pathogen but also presents its antigens on the surface of the phagocyte, aiding in the activation of other immune cells.
Step 2
Explain how antibodies are produced in response to the entry of a pathogen.
Answer
When a pathogen enters the body, it carries specific proteins known as antigens that are recognized as foreign by the immune system. This triggers an immune response. The first step involves antigen-presenting cells, like phagocytes, that ingest the pathogen and present its antigens on their surface.
The presented antigen is recognized by a specific B cell that is programmed to respond to that particular antigen. Once the B cell binds to the antigen, it becomes activated and undergoes clonal selection, resulting in the proliferation of specific B cells. These activated B cells then differentiate into plasma cells, which produce large quantities of antibodies that are specific to the pathogen's antigens. Consequently, these antibodies circulate in the bloodstream, neutralizing the pathogen and marking it for destruction by other immune cells.