A Level Biology Practice Exam

Which of the following describes opsonins?

1. Chemicals that induce inflammation

2. Chemicals that bind to pathogens and tag them for recognition by phagocytes

3. Proteins that neutralize toxins

4. Cellular structures involved in metabolism

The correct answer is: Chemicals that bind to pathogens and tag them for recognition by phagocytes

The correct choice identifies opsonins as substances that bind to pathogens and facilitate their recognition and uptake by phagocytic cells such as macrophages and neutrophils. This process is crucial for the immune response, as opsonins enhance the ability of phagocytes to identify, engulf, and destroy pathogens. By coating pathogens, opsonins make them more recognizable to immune cells, effectively tagging them for destruction and thereby aiding in the clearance of infections. The other choices do not accurately capture the function of opsonins. While chemicals that induce inflammation play important roles in the immune response, they are distinct from opsonins. Similarly, proteins that neutralize toxins focus on mitigating harmful effects rather than enhancing recognition of pathogens. Lastly, cellular structures involved in metabolism pertain to the functions and organization of cells rather than their immune interactions.