Active transport processes

Active transport processes - vesicle There are three kinds...

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Active transport processes Active transport is the movement of solutes against a gradient and requires the expenditure of energy (usually ATP). Active transport is achieved through one of the following two mechanisms: Transport proteins in the plasma membrane transfer solutes such as small ions (Na + , K + , Cl , H + ), amino acids, and monosaccharides. Vesicles or other bodies in the cytoplasm move macromolecules or large particles across the plasma membrane. Types of vesicular transport include the following: Exocytosis, which describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell. This process is common when a cell produces substances for export. Endocytosis, which describes the capture of a substance outside the cell when the plasma membrane merges to engulf it. The substance subsequently enters the cytoplasm enclosed in a
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Unformatted text preview: vesicle. There are three kinds of endocytosis: • Phagocytosis (“cellular eating”) occurs when undissolved material enters the cell. The plasma membrane engulfs the solid material, forming a phagocytic vesicle. • Pinocytosis (“cellular drinking”) occurs when the plasma membrane folds inward to form a channel allowing dissolved substances to enter the cell. When the channel is closed, the liquid is enclosed within a pinocytic vesicle. • Receptor-mediated endocytosis occurs when specific molecules in the fluid surrounding the cell bind to specialized receptors in the plasma membrane. As in pinocytosis, the plasma membrane folds inward and the formation of a vesicle follows. Certain hormones are able to target specific cells by receptor-mediated endocytosis....
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