Book Show In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan. 2022 Sep 12. Affiliations
Free Books & Documents Book Physiology, Active TransportIsaac Chen et al. Free Books & Documents ExcerptThere are two main modes of transport of molecules across any biological membrane. These are passive and active transport. Passive transport, most commonly by diffusion, occurs along a concentration gradient from high to low concentration. No energy is necessary for this mode of transport. Examples will include diffusion of gases across alveolar membranes and diffusion of neurotransmitters such as acetylcholine across the synapse or neuromuscular junction. Osmosis is a form of passive transport when water molecules move from low solute concentration(high water concentration) to high solute or low water concentration across a membrane that is not permeable to the solute. There is a form of passive transport called facilitated diffusion. It occurs when molecules such as glucose or amino acids move from high concentration to low concentration facilitated by carrier proteins or pores in the membrane. Active transport requires energy for the process by transporting molecules against a concentration or electrochemical gradient. Active transport is an energy-driven process where membrane proteins transport molecules across cells, mainly classified as either primary or secondary, based on how energy is coupled to fuel these mechanisms. The former constitutes means by which a chemical reaction, e.g., ATP hydrolysis, powers the direct transport of molecules to establish specific concentration gradients, as seen with sodium/potassium-ATPase and hydrogen-ATPase pumps. The latter employs those established gradients to transport other molecules. These gradients support the roles of other membrane proteins and other workings of the cell and are crucial to the maintenance of cellular and bodily homeostasis. As such, the importance of active transport is apparent when considering the various defects throughout the body that can manifest in a wide variety of diseases, including cystic fibrosis and cholera, all because of an impairment in some aspect of active transport. Copyright © 2022, StatPearls Publishing LLC. Sections
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Is primary active transport is driven by secondary active transport?Primary active transport is driven by secondary active transport.
What is primary active transport driven by?Primary active transport occurs in the absence of or against the existing electrochemical gradient, and is powered by metabolic energy, such as that originated by the exergonic hydrolysis of ATP (Fig. 6). Ion pumps are the only molecules capable of performing primary active transport.
What is true about secondary active transport?Unlike in primary active transport, in secondary active transport, ATP is not directly coupled to the molecule of interest. Instead, another molecule is moved up its concentration gradient, which generates an electrochemical gradient. The molecule of interest is then transported down the electrochemical gradient.
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Primary active transport is driven by secondary active transport true or False
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