A pancreatic beta cell synthesizes insulin, a large protein hormone, and then releases it into the bloodstream to regulate blood glucose levels. Which cellular process is primarily responsible for the release of insulin from the pancreatic beta cell?
Show answer and explanation
The answer
Correct answer: B. Exocytosis, which involves the fusion of secretory vesicles with the plasma membrane to expel substances.
Tested concept: Endocytosis and exocytosis
Explanation
The release of large molecules like protein hormones (e.g., insulin) from a cell into the extracellular environment is accomplished through exocytosis. This process involves the packaging of substances into vesicles within the cell, which then move to the plasma membrane, fuse with it, and release their contents outside. Endocytosis is the opposite process, bringing substances into the cell. Active transport and facilitated diffusion are mechanisms for moving smaller molecules or ions across the membrane, not for the bulk transport of large proteins via vesicles.
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