Cells need to move not only small ions and molecules but also larger particles and bulk quantities of material across the plasma membrane. This lesson explains endocytosis, the energy-requiring process cells use to bring material inside.
A large particle cannot pass directly through the plasma membrane, even when the cell supplies energy. Instead, the membrane changes shape around the material. In endocytosis, the plasma membrane folds inward, or invaginates, to form a pocket around the target. The pocket then pinches off, enclosing the material inside a new intracellular vesicle.
All flashcards
What is endocytosis?
An energy-requiring process in which the plasma membrane encloses material in a vesicle to bring it into the cell.
What does phagocytosis do?
It engulfs large particles, such as microorganisms, in a membrane-bound vesicle.
How does pinocytosis differ from phagocytosis?
Pinocytosis takes in extracellular fluid and dissolved substances; phagocytosis engulfs large particles.
What are caveolae, and what role does caveolin play?
Caveolae are small membrane pockets; caveolin helps form them during potocytosis.
What is exocytosis?
The release of vesicle contents outside a cell when an internal vesicle fuses with the plasma membrane.
Quiz questions
Why is endocytosis classified as active transport?Answer: It requires cellular energy to move material into the cell in vesicles.
What happens when a vesicle releases its contents by exocytosis?Answer: The vesicle fuses with the plasma membrane and opens to the cell exterior.
After a phagocytic vesicle enters a cell, what can digest its captured material?Answer: A lysosome can fuse with the vesicle, and its enzymes break down the material.
Why can defective LDL receptors cause high blood cholesterol in familial hypercholesterolemia?Answer: Cells take up LDL from the blood less effectively through receptor-mediated endocytosis.
What distinguishes bulk transport from transport through a membrane protein?Answer: Bulk transport moves material in membrane-bound vesicles rather than one molecule at a time.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.