Pinocytosis - Example Cholesterol is carried by...

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Pinocytosis Pinocytosis refers to engulfing macromolecules. As in phagocytosis, a vesicle is formed which contains the molecules that were brought into the cell. Vacuoles and vesicles produced by phagocytosis and pinocytosis can fuse with lysosomes (lysosomes are vesicles that contain digestive enzymes). Phagocytosis and pinocytosis remove membrane from cell surface to form vacuoles that contain the engulfed material. Receptor-Mediated endocytosis Macromolecules bind to receptors on the surface of the cell. Receptors with bound macromolecules aggregate in one area and are brought into the cell by endocytosis. The vesicle containing the macromolecules can release the macromolecules into the cell directly or they can be processed by chemicals contained within lysosomes after fusing with the lysosomes. The vesicle (and receptors) then returns to the cell surface.
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Unformatted text preview: Example: Hypercholesterolemia Cholesterol is carried by LDL (low-density lipoprotein), which binds to LDL receptors on the cell surface. Normally cholesterol (and LDL) is brought into the cell by receptor-mediated endocytosis as described above. A faulty gene for the LDL receptor results in LDL not binding to the cells. The Cholesterol remains in the blood and becomes deposited on arteries. Reduced blood flow in arteries that supply the heart causes heart attacks in patients as early as 6 years. Exocytosis Exocytosis moves material to the outside. A vesicle fuses with the plasma membrane and discharges its contents outside. This allows cells to secrete molecules. The fusion of vesicles to the plasma membrane adds membrane to the cell surface....
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