A Level Biology Practice Exam

What is phagocytosis primarily associated with?

1. The digestion of food

2. The defense against pathogens

3. The absorption of nutrients

4. The transport of oxygen

The correct answer is: The defense against pathogens

Phagocytosis is primarily associated with the defense against pathogens. This process involves specialized immune cells, known as phagocytes, which include macrophages and neutrophils. These cells recognize, engulf, and digest cellular debris, foreign substances, and pathogens such as bacteria and viruses. The ability of phagocytes to effectively identify and internalize these harmful entities is crucial for the immune response, helping to eliminate infections and protect the body from disease. During phagocytosis, the phagocyte surrounds the pathogen, forms a phagosome, and then fuses it with lysosomes containing digestive enzymes, leading to the breakdown of the pathogen. The other choices pertain to different biological processes. For instance, the digestion of food involves enzymes breaking down nutrients but does not directly involve phagocytosis. Likewise, absorption of nutrients generally occurs in the intestines through mechanisms such as diffusion and active transport rather than phagocytosis. The transport of oxygen is primarily the role of red blood cells and hemoglobin, not phagocytic activity. Thus, understanding the specific role of phagocytosis in the immune system context clarifies why it is associated with defending against pathogens.