A pancreatic beta cell synthesizes insulin, a large protein hormone, and needs to secrete it into the bloodstream. Which cellular process is primarily responsible for releasing this large molecule from the cell into the extracellular space?
Show answer and explanation
The answer
Correct answer: B. Exocytosis involves the fusion of a secretory vesicle with the plasma membrane to release its contents outside the cell.
Tested concept: Endocytosis and exocytosis
Explanation
Exocytosis is the correct process for releasing large molecules, such as protein hormones like insulin, from the cell. It involves the packaging of these molecules into vesicles, which then move to the plasma membrane, fuse with it, and release their contents into the extracellular space. Endocytosis is the opposite process, where the cell takes in substances from the extracellular environment. Active transport typically moves smaller ions or molecules across the membrane, often against their concentration gradient, but does not involve vesicles for large protein secretion. Osmosis is the movement of water across a semipermeable membrane and is not directly involved in the secretion of large protein molecules.
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