College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What process do white blood cells use to engulf and digest bacteria at an infection site?

1. Diffusion

2. Phagocytosis

3. Exocytosis

4. Osmosis

The correct answer is: Phagocytosis

Phagocytosis is the process by which white blood cells, such as macrophages and neutrophils, engulf and digest bacteria and other pathogens at sites of infection. During phagocytosis, the white blood cell identifies the bacteria, binds to it, and then extends its membrane to surround the pathogen, effectively engulfing it in a process that forms a vesicle known as a phagosome. Once the bacteria are enclosed, digestive enzymes within the cell are released into the phagosome, breaking down the bacteria and rendering them harmless. This method is crucial for the immune response, enabling the body to remove harmful microorganisms effectively. By choosing this process, the body utilizes its specialized white blood cells to maintain health and protect against infections, ensuring that the immune system functions optimally in response to pathogens. Other processes mentioned, such as diffusion and osmosis, involve the movement of particles across membranes but do not specifically pertain to the active ingestion of pathogens. Exocytosis is a process where substances are expelled from cells, which is the opposite of what occurs in phagocytosis. Thus, phagocytosis stands out as the correct and vital mechanism for the immune response to bacterial infections.