Which is the correct progressive sequence of steps in phagocytosis?

Which is the correct progressive sequence of steps in phagocytosis?

• A. Adherence, chemotaxis, ingestion, digestion
• B. Ingestion, adherence, chemotaxis, digestion
• C. Chemotaxis, adherence, ingestion, digestion
• D. Ingestion, digestion, chemotaxis, adherence

Answer: (C)

Phagocytosis unfolds in a specific sequence: chemotaxis, adherence, ingestion, digestion. First, the phagocyte senses chemical signals from the invading organism or damaged tissue and moves toward it (chemotaxis). Once it reaches the target, it binds to it (adherence), a step that can be enhanced if the pathogen is opsonized by antibodies or complement. After attaching, the phagocyte engulfs the target, forming a phagosome (ingestion). Finally, lysosomes fuse with the phagosome to form a phagolysosome, where enzymes digest the contents (digestion). This order matters because you must locate and attach to the target before you can ingest it, and you must ingest it before you can digest it.

Phagocytosis unfolds in a specific sequence: chemotaxis, adherence, ingestion, digestion. First, the phagocyte senses chemical signals from the invading organism or damaged tissue and moves toward it (chemotaxis). Once it reaches the target, it binds to it (adherence), a step that can be enhanced if the pathogen is opsonized by antibodies or complement. After attaching, the phagocyte engulfs the target, forming a phagosome (ingestion). Finally, lysosomes fuse with the phagosome to form a phagolysosome, where enzymes digest the contents (digestion). This order matters because you must locate and attach to the target before you can ingest it, and you must ingest it before you can digest it.