Ion pumps and ion exchangers

11 Ion pumps and ion exchangers





Questions



image What is the normal distribution of ions across the plasma membrane of a resting cell?

image How do the activities of ion pumps and exchangers differ?

image What are the roles of the Na+/K+-ATPase in cellular physiology?

image How do transport proteins contribute to the maintenance of a low intracellular Ca2+ concentration?


Ion distribution across the plasma membrane


Gradients are maintained (outside/inside) for Na+(145/10 mmol/l), K+ (4.5/160mmol/l), Ca2+ (1.5/<0.0001mmol/l) and Cl− (114/3 mmol/l) across the plasma membrane by the activity of ATP-dependent ion pumps and ion exchangers.



ATP-dependent ion pumps


Ion pumps derive the energy to transport ions across membranes against their electrochemical gradient by using the energy of ATP hydrolysis directly. A number of important ion-transporting ATPases make important contributions to cellular physiology (Fig. 3.11.1 and Ch. 12).


image

Fig. 3.11.1 Ion-transporting ATPases in ion homeostasis.



The Na+/K+-ATPase or Na+ pump


The Na+/K+-ATPase is found in all cells and is crucial to the maintenance of the gradients for Na+ and K+ across the plasma membrane in resting cells. Creation of these gradients is important to provide the driving forces for processes such as the regulation of resting membrane potential (Ch. 17

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Jun 18, 2016 | Posted by in BIOCHEMISTRY | Comments Off on Ion pumps and ion exchangers

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