19. The diagram illustrates the process of endocytosis. If
the particles are small, the type of endocytosis would be known as pinocytosis.
If the particles are large, then it would be known as phagocytosis.
The particles have probably activated a receptor on the outer
surface of the membrane. The cell then uses ATP energy to contract the cell
membrane inward, forming a small pocket. As the pocket continues to fold inward,
it eventually forms a vacuole which is completely independent of the plasma
membrane. The vacuole is then free to move throughout the cytoplasm as needed.
Note that the vacuole has the same lipid bilayer as the plasma
membrane!
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Slichter