3.5 Active Transport, Endocytosis, and Exocytosis KEY CONCEPT Cells use energy (ATP) to transport materials that cannot diffuse across a membrane. Video: Comparing Passive and Active Transport

3.5 Active Transport, Endocytosis, and Exocytosis Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient. Passive transport requires no energy from the cell. Active transport is powered by chemical energy (ATP). Active transport occurs through transport protein pumps. Cells use active transport to maintain homeostasis. Synthesize: In what ways are active transport proteins similar to enzymes?

3.5 Active Transport, Endocytosis, and Exocytosis A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis. Cells use energy (ATP) to transport material in vesicles. Endocytosis is the process of taking material into the cell. Phagocytosis is a type of endocytosis in which the cell membrane engulfs large particles. Sometimes is called “cell eating”. During endocytosis, the cell membrane folds inward and fuses together surrounding the substance in a pocket . The vesicle fuses with a lysosome, or a similar vesicle, where enzymes break down the membrane and its contents. The pocket pinches off inside the cell, forming a vesicle.

3.5 Active Transport, Endocytosis, and Exocytosis A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis. Cells use energy (ATP) to transport material in vesicles. Exocytosis is the process of expelling material from the cell. The cell forms a vesicle around material that needs to be removed or secreted. The vesicle is transported to the cell membrane. The vesicle membrane fuses with the cell membrane and releases the contents.

Examples of Endocytosis and Exocytosis Exocytosis – plays a role in the human immune system. White blood cells called macrophages help your body fight infection by engulfing and destroying materials that do not belong in your body like bacteria cells. Endocytosis – plays a role in the human nervous system. Vesicles within nerve cells carry and release chemicals to other cells to transmit nerve impulses that for example, will cause your muscles to contract. Hypothesize: What might happen if vesicles in your neurons were suddenly unable to fuse with the cell membrane?