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The US Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. [6] See table. The European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg. [10]
Calcium is a chemical element essential for living organisms, involved in many biological processes.
The resting concentration of Ca 2+ in the cytoplasm is normally maintained around 100 nM.This is 20,000- to 100,000-fold lower than typical extracellular concentration. [1] [2] To maintain this low concentration, Ca 2+ is actively pumped from the cytosol to the extracellular space, the endoplasmic reticulum (ER), and sometimes into the mitochondria.
Calcium release-activated channels (CRAC) are specialized plasma membrane Ca 2+ ion channels. When calcium ions (Ca 2+) are depleted from the endoplasmic reticulum (a major store of Ca 2+) of mammalian cells, the CRAC channel is activated to slowly replenish the level of calcium in the endoplasmic reticulum.
Voltage-gated calcium channels (VGCCs), also known as voltage-dependent calcium channels (VDCCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g. muscle, glial cells, neurons) with a permeability to the calcium ion Ca 2+.
L-type Calcium Channels contain 5 different subunits, the α1(170–240 kDa), α2(150kDa), δ(17-25 kDa), β(50-78 kDa), and γ(32 kDa) subunits. [8] The α2, δ, and β subunits are non-covalently bonded to the α1 subunit and modulate ion trafficking and biophysical properties of the α1 subunit.
Calcium-activated potassium channels are potassium channels gated by calcium, [1] or that are structurally or phylogenetically related to calcium gated channels. They were first discovered in 1958 by Gardos [who?] who saw that calcium levels inside of a cell could affect the permeability of potassium through that cell membrane.
The sodium-calcium exchanger (often denoted Na + /Ca 2+ exchanger, exchange protein, or NCX) is an antiporter membrane protein that removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium (Na +) by allowing Na + to flow down its gradient across the plasma membrane in exchange for the countertransport of calcium ions (Ca 2+).