Which sequence describes endocytosis?

Which sequence describes endocytosis?

• A. Plasma membrane surrounds material to be transported into the cell, edges of membrane meet, membranes fuse to form vesicles
• B. Vesicle carries material to the nucleus
• C. Vesicle fuses with plasma membrane to expel material
• D. Materials simply pass through channels

Answer: (A)

Endocytosis is the process by which a cell takes in material by wrapping the plasma membrane around it to form a vesicle inside the cell. The sequence shown—plasma membrane surrounds the material, the edges meet, and membranes fuse to form vesicles—precisely describes the membrane invagination and vesicle formation that internalizes substances. This is how pinocytosis and phagocytosis occur, using energy and cytoskeletal changes to pinch off a vesicle. The other options describe different processes: one is about vesicles moving to another part of the cell, not the uptake step; another describes exocytosis, where vesicles fuse with the plasma membrane to release material outside the cell; and another describes diffusion or channel-mediated transport, which doesn't involve vesicle formation.

Endocytosis is the process by which a cell takes in material by wrapping the plasma membrane around it to form a vesicle inside the cell. The sequence shown—plasma membrane surrounds the material, the edges meet, and membranes fuse to form vesicles—precisely describes the membrane invagination and vesicle formation that internalizes substances. This is how pinocytosis and phagocytosis occur, using energy and cytoskeletal changes to pinch off a vesicle.

The other options describe different processes: one is about vesicles moving to another part of the cell, not the uptake step; another describes exocytosis, where vesicles fuse with the plasma membrane to release material outside the cell; and another describes diffusion or channel-mediated transport, which doesn't involve vesicle formation.