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What Is an Ion Channel?

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Ion channel, protein expressed by virtually all living cells that creates a pathway for charged ions from dissolved salts, including sodium, potassium, calcium, and chloride ions, to pass through the otherwise impermeant lipid cell membrane

Operation of cells in the nervous system, contraction of the heart and of skeletal muscle, and secretion in the pancreas are examples of physiological processes that require ion channels. In addition, ion channels in the membranes of intracellular organelles are important for regulating cytoplasmic calcium concentration and acidification of specific subcellular compartments.

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Specific macromolecular transport systems, ion channels and pumps, provide the pathways to facilitate and control the passage of ions across the lipid membrane. Ion channels provide energetically favourable passage for ions to diffuse rapidly and passively according to their electrochemical potential. Selective ion channels are essential for the excitability of biological membranes: the action potential is a transient phenomenon that reflects the rapid opening and closing of voltage-dependent Na+-selective and K+-selective channels. One of the most critical functional aspects of K+ channels is their ability to remain highly selective for K+ over Na+ while allowing high-throughput ion conduction at a rate close to the diffusion limit. Permeation through the K+ channel selectivity filter is believed to proceed as a ‘knockon’ mechanism, in which 2–3 K+ ions interspersed by water molecules move in a single file

Permeation through the comparatively wider and less selective Na+ channels also proceeds via a loosely coupled knockon mechanism, although the ions do not need to be fully dehydrated. While simple structural concepts are often invoked to rationalize the mechanism of ion selectivity, a deeper analysis shows that subtle effects play an important role in these flexible dynamical structures.

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Specific macromolecular transport systems, ion channels and pumps, provide the pathways to facilitate and control the passage of ions across the lipid membrane. Ion channels provide energetically favorable passage for ions to diffuse rapidly and passively according to their electrochemical potential. Selective ion channels are essential for the excitability of biological membranes: the action potential is a transient phenomenon that reflects the rapid opening and closing of voltage-dependent Na+-selective and K+-selective channels (Åqvist J, V, Luzhkov B., 2000). One of the most critical functional aspects of K+ channels is their ability to remain highly selective for K+ over Na+ while allowing high-throughput ion conduction at a rate close to the diffusion limit. Permeation through the K+ channel selectivity filter is believed to proceed as a “knock-on” mechanism in which 2–3 K+ ions interspersed by water molecules move in single file. Permeation through the comparatively wider and less selective Na+ channels also proceeds via a loosely coupled knock-on mechanism, although the ions do not need to be fully dehydrated (Bagneris C, Naylor CE, 2015). While simple structural concepts are often invoked to rationalize the mechanism of ion selectivity, a deeper analysis shows that subtle effects play an important role in these flexible dynamical structures.

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In conclusion, the drug, carbenoxelone shows that there may not be any gap junctions present in the daphnia heart, therefore an alternative method may be used for intercellular signal transmission. Overall the daphnia could be used to show the effects of the Lidocaine, Verapamil and 4 – Aminopyridine on the heart, therefore the daphnia heart is a useful educational tool, to show the effects of drugs on the heart. The fact the daphnia is one cell thick and transparent makes it straightforward to find the heart under the microscope

Therefore the daphnia can be used for educational purposes in undergraduate study.

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Åqvist J, V, Luzhkov B. Ion permeation mechanism of the potassium channel. Nature. 2000;404:881–884.

Bagneris C, Naylor CE, McCusker EC, Wallace BA. Structural model of the open-closed-inactivated cycle of prokaryotic voltage-gated sodium channels. The Journal of general physiology. 2015

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