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You are watching: Why is atp required for membrane pump systems to operate

Berg JM, Tymoczko JL, Stryer L. Biochemistry. 5th edition. Brand-new York: W H Freeman; 2002.


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Figure

The flow of ions through a single membrane channel (channels are shown in red in the illustration in ~ the left) can be recognize by the patch clamp technique, which records current transforms as the channel transits in between the open and closed states. <(Left) (more...)


The lipid double layer of biological membranes, as discussed in chapter 12, is fundamentally impermeable come ions and also polar molecules. Permeability is conferred by two classes of membrane proteins, pumps and also channels. Pumps usage a source of totally free energy such together ATP or irradiate to journey the thermodynamically uphill move of ions or molecules. Pump activity is an instance of energetic transport. Channels, in contrast, enable ions to flow rapidly v membranes in a downhill direction. Channel activity illustrates passive transport, or helped with diffusion.

Pumps are energy transducers in the they convert one kind of totally free energy into another. Two species of ATP-driven pumps, P-type ATPases and the ATP-binding cassette pumps, undergo conformational transforms on ATP binding and also hydrolysis that cause a tied ion to be transported across the membrane. Phosphorylation and dephosphorylation that both the Ca2+-ATPase and the Na+-K+-ATPase pumps, which are representative the P-type ATPase, space coupled to alters in orientation and also affinity of their ion-binding sites.

A different mechanism of energetic transport, one that utilizes the gradient that one ion to journey the active transport the another, will be depicted by the sodium—calcium exchanger. This pump plays an essential role in extruding Ca2+ native cells.

We start our examination of channels with the acetylcholine receptor, a channel the mediates the transmission of nerve signals throughout synapses, the useful junctions between neurons. The acetylcholine receptor is a ligand-gated channel in the the channel opens up in solution to the binding that acetylcholine (Figure 13.1). In contrast, the sodium and also potassium channels, i beg your pardon mediate activity potentials in neuron axon membranes, are opened by membrane depolarization fairly than by the binding of an allosteric effector. These networks are voltage-gated. These networks are also of interest due to the fact that they swiftly and also deftly distinguish between quite similar ions (e.g., Na+ and K+). The circulation of ions v a single channel in a membrane can readily it is in detected by utilizing the patch-clamp technique.


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Figure 13.1

Acetylcholine Receptors. An electron micrograph mirrors the densely pack acetylcholine receptors embedded in a postsynaptic membrane.


The chapter concludes with a check out of a various kind of channel—the cell-to-cell channel, or void junction. These channels permit the deliver of ions and metabolites between cells.

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13.1. The transport of Molecules across a Membrane might Be active or Passive13.2. A household of Membrane Proteins supplies ATP Hydrolysis to Pump Ions throughout Membranes13.3. Multidrug Resistance and Cystic Fibrosis highlight a family of Membrane Proteins through ATP-Binding Cassette Domains13.4. Secondary Transporters usage One Concentration Gradient to strength the development of Another13.5. Particular Channels can Rapidly transport Ions throughout Membranes13.6. Void Junctions allow Ions and small Molecules come Flow in between Communicating CellsSummaryProblemsSelected Readings

By covenant with the publisher, this book is accessible by the search feature, however cannot it is in browsed.