Đang tải... (xem toàn văn)
(BQ) Part 2 book Cellular physiology and neurophysiology presents the following contents: Active transport, physiology of synaptic transmission, synaptic physiology ii, molecular motors and Muscle contraction, excitation-contraction coupling in muscle, mechanics of muscle contraction.
11 ACTIVE TRANSPORT O BJECTIVES Understand how the Na1 pump uses energy from ATP to keep [Na1]i low and [K1]i high by transporting Na1 and K1 against their electrochemical gradients 4 Understand the roles of ATP-dependent transport systems in the transport of such ions as protons and copper, as well as a variety of other solutes 2 Understand how Ca21 is sequestered in the sarcoplasmic and endoplasmic reticulum and transported across the plasma membrane by ATP-dependent active transport systems 5 Understand how different transport systems in the apical and basolateral membranes of epithelia, which separate two different extracellular compartments, act cooperatively to effect net transfer of solutes and water across epithelial cells 3 Understand how intracellular Ca21 is controlled and Ca21 signaling is regulated by the cooperative action of many transport systems PRIMARY ACTIVE TRANSPORT CONVERTS THE CHEMICAL ENERGY FROM ATP INTO ELECTROCHEMICAL POTENTIAL ENERGY STORED IN SOLUTE GRADIENTS In Chapter 10, we learned how energy stored in the Na1 electrochemical gradient can be used to generate concentration (or electrochemical) gradients for other (coupled) solutes This is called secondary active transport because a preexisting electrochemical energy gradient is dissipated in one part of the transport process (e.g., the downhill movement of Na1) to generate the chemical or electrochemical gradients of other solutes (e.g., glucose or Ca21) There is no net expenditure of metabolic energy by these transporters The question we need to address here is: How does the Na1 concentration gradient (typically, [Na1]o/ [Na1]i