Endocytosis and Exocytosis

I. During endocytosis, regions of the plasma membrane invaginate and pinch off to form vesicles that enclose a small volume of extracellular material.

a. The three classes of endocytosis are (1) fluid endocytosis, (2) adsorptive endocytosis, and (3) phagocytosis.

b. Most endocytotic vesicles fuse with endosomes, which in turn transfer the vesicle contents to lysosomes where they are digested by lysosomal enzymes.

II. Exocytosis, which occurs when intracellular vesicles fuse with the plasma membrane, provides a means

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

PART ONE Basic Cell Functions of adding components to the plasma membrane and a route by which membrane-impermeable molecules, such as proteins synthesized by cells, can be released into the extracellular fluid.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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