Search results
Results From The WOW.Com Content Network
Natural calcium is a mixture of five stable isotopes (40 Ca, 42 Ca, 43 Ca, 44 Ca, and 46 Ca) and one isotope with a half-life so long that it is for all practical purposes stable (48 Ca, with a half-life of about 4.3 × 10 19 years). Calcium is the first (lightest) element to have six naturally occurring isotopes.
The Ca 2+ concentration of the vacuole may reach millimolar levels. The most striking use of Ca 2+ ions as a structural element in algae occurs in the marine coccolithophores, which use Ca 2+ to form the calcium carbonate plates, with which they are covered. Calcium is needed to form the pectin in the middle lamella of newly formed cells.
About 2 g of calcium-48. Calcium-48 is a doubly magic nucleus with 28 neutrons; unusually neutron-rich for a light primordial nucleus. It decays via double beta decay with an extremely long half-life of about 6.4×10 19 years, though single beta decay is also theoretically possible. [22]
Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life. [ 3 ] [ 63 ] Selenium acts as the catalytic center of several antioxidant enzymes, such as glutathione peroxidase , [ 11 ] and plays a wide variety of other biological roles .
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Ca 2+ is important for cellular signalling, for once it enters the cytosol of the cytoplasm it exerts allosteric regulatory effects on many enzymes and proteins. Ca 2+ can act in signal transduction resulting from activation of ion channels or as a second messenger caused by indirect signal transduction pathways such as G protein-coupled receptors.
The most ubiquitous Ca 2+-sensing protein, found in all eukaryotic organisms including yeasts, is calmodulin. Intracellular storage and release of Ca 2+ from the sarcoplasmic reticulum is associated with the high-capacity, low-affinity calcium-binding protein calsequestrin. [3] Calretinin is another type of Calcium binding protein weighing 29kD ...
These elements originally referred to earth, water, air and fire rather than the chemical elements of modern science. The term 'elements' ( stoicheia ) was first used by Greek philosopher Plato around 360 BCE in his dialogue Timaeus , which includes a discussion of the composition of inorganic and organic bodies and is a speculative treatise on ...