Calcium: Difference between revisions
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Calcium is used in many different signaling pathways, i.e. through [[G-proteins|G proteins]], | Calcium is used in many different signaling pathways, i.e. through [[G-proteins|G proteins]], ion channel. | ||
Every person starts out as a | Every person starts out as a calcium wave. The wave triggered during fertilization it stops multiple sperm from fertilizing the ovum. <br>Calcium is used as an intracellular messenger as it is kept at low levels in resting cells; cells have many sensitive mechanisms that detect rises and falls in Calcium levels. | ||
[[ | "OFF" mechanisms are important in the recovery of intracellular calcium levels, particularly in [[muscle|muscle]] cells, as the cell cannot contract again until calcium levels fall after the rise associated with [[contraction|contraction]]. "OFF" mechanisms include buffer proteins in the [[sarcoplasmic reticulum|sarcoplasmic reticulum]] (e.g. [[calsequestrin|Calsequestrin]]). These proteins have low affinity and high capacity for calcium, so that it is still easily released for signalling. Another "OFF" mechanism is Na<sup>+</sup>/Ca<sup>2+</sup> exchanger pump in the [[plasma membrane|plasma membrane]], which operates at higher levels of Ca<sup>2+. </sup>The differences in affinity of the "OFF" mechanisms for calcium allow the cell to respond effectively to different concentrations. PMCA and SERCA also keep cytosolic Ca<sup>2+</sup> levels low by utilising [[ATP|ATP]] to pump Ca<sup>2+</sup> out of the cytosol into the [[endoplasmic reticulum|E.R]]., [[sarcoplasmic reticulum|S.R]]., or outside the cell. | ||
"ON" mechanisms respond to extracellular signals indicating to increase the levels of cytosolic Ca<sup>2+</sup>. These include InsP<sub>[[InsP3 receptor|3]] </sub>and [[ryanodine receptor|Ryanodine receptors]], both which are activated by the binding of [[ATP|ATP]], however, [[InsP3 receptors|InsP<sub>3</sub> receptors]] also require binding of the coagonist [[InsP3|InsP<sub>3</sub>]] to activate them. | |||
=== References: === | === References: === | ||
<references /><br> | <references /><br> | ||
Revision as of 22:46, 23 November 2010
Calcium is used in many different signaling pathways, i.e. through G proteins, ion channel.
Every person starts out as a calcium wave. The wave triggered during fertilization it stops multiple sperm from fertilizing the ovum.
Calcium is used as an intracellular messenger as it is kept at low levels in resting cells; cells have many sensitive mechanisms that detect rises and falls in Calcium levels.
"OFF" mechanisms are important in the recovery of intracellular calcium levels, particularly in muscle cells, as the cell cannot contract again until calcium levels fall after the rise associated with contraction. "OFF" mechanisms include buffer proteins in the sarcoplasmic reticulum (e.g. Calsequestrin). These proteins have low affinity and high capacity for calcium, so that it is still easily released for signalling. Another "OFF" mechanism is Na+/Ca2+ exchanger pump in the plasma membrane, which operates at higher levels of Ca2+. The differences in affinity of the "OFF" mechanisms for calcium allow the cell to respond effectively to different concentrations. PMCA and SERCA also keep cytosolic Ca2+ levels low by utilising ATP to pump Ca2+ out of the cytosol into the E.R., S.R., or outside the cell.
"ON" mechanisms respond to extracellular signals indicating to increase the levels of cytosolic Ca2+. These include InsP3 and Ryanodine receptors, both which are activated by the binding of ATP, however, InsP3 receptors also require binding of the coagonist InsP3 to activate them.
References: