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The hydrolysis starts with the enzyme PI 4-kinase alpha converting PI into PI 4-phosphate , which is then converted into PI (4,5) biphosphate (PI(4,5)P 2) by the enzyme PI 4-phosphate-5-kinase . PI(4,5)P 2 is then hydrolysed by phospholipase C ( PLC ) and forms the second messengers, inositol (1,4,5) triphosphate ( IP 3 ) and diacylglycerol ( DG ).
Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)P 2, also known simply as PIP 2 or PI(4,5)P 2, is a minor phospholipid component of cell membranes. PtdIns(4,5)P 2 is enriched at the plasma membrane where it is a substrate for a number of important signaling proteins. [1] PIP2 also forms lipid clusters [2] that sort proteins. [3] [4] [5]
Any area on a sphere which is equal in area to the square of its radius, when observed from its center, subtends precisely one steradian. The solid angle of a sphere measured from any point in its interior is 4 π sr. The solid angle subtended at the center of a cube by one of its faces is one-sixth of that, or 2 π /3 sr.
Between the square and the circle are four segments. If the total area of those gaps, G 4, is greater than E, split each arc in half. This makes the inscribed square into an inscribed octagon, and produces eight segments with a smaller total gap, G 8. Continue splitting until the total gap area, G n, is less than E.
The number π (/ p aɪ / ⓘ; spelled out as "pi") is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter.It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining π, to avoid relying on the definition of the length of a curve.
It has been found that a circular area is to the square on a line equal to the quadrant of the circumference, as the area of an equilateral rectangle is to the square on one side. [12] An "equilateral rectangle" is, by definition, a square. This is an assertion that the area of a circle is the same as that of a square with the same perimeter.
A sphere of radius r has surface area 4πr 2.. The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies. [1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with ...
where C is the circumference of a circle, d is the diameter, and r is the radius.More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width.