What is the process called when cells take in larger particles through the cell membrane?

• A. Endocytosis
• B. Pinocytosis
• C. Receptor-mediated endocytosis
• D. Phagocytosis

Answer: (D)

The process of taking in larger particles through the cell membrane is known as phagocytosis. This is a specific type of endocytosis where cells engulf large particles, such as pathogens or cellular debris, by extending their membrane around the material and forming a vesicle. This vesicle then typically fuses with lysosomes, where the engulfed material can be broken down and processed.

Phagocytosis is crucial for the immune response, allowing immune cells, like macrophages and neutrophils, to eliminate foreign substances and maintain homeostasis. In contrast to phagocytosis, pinocytosis refers to the uptake of fluid and small solutes, while receptor-mediated endocytosis involves the selective uptake of substances based on the binding of specific ligands to receptors on the cell surface. Regardless of these other mechanisms, phagocytosis is characterized primarily by its ability to internalize larger, solid particles.