Cholesterol
The cholesterol, also more accurate cholesterol ( Greek χολή
cholé, Galle ' and στερεός stereos, reliable, rigid, hardened' ), is an
occurring in all animal cells crystalline, fat-like natural substance. The
name, coined in 1824 by the chemist Michael Eugène Chevreul, is derived from
the fact that cholesterol was found in gallstones as early as the 18th century was
found. Aside from bile, the liver's cholesterol is also abundant in the brain,
nerves, and blood. Cholesterol plays a role in the steadying of cell membranes
and nerve occupation, is essential for the production of sex hormones and other
processes.
Cholesterol was also found in small amounts in plant cells (
potato tops, pollen, isolated chloroplasts ) and bacteria. A particularly
cholesterol vegetable oils were corn oil (55 mg per kg), rapeseed oil (53 mg
per kg), and cottonseed oil (45 mg per kg) identified. Typical sources of
cholesterol of animal origin contain many times this level. For example, butter has a cholesterol content
of 2340 mg per kg.
Function
Cholesterol is a vital sterol and an essential part of the
cell membrane. It raises the membrane's stability and, together with proteins,
helps smuggle signal substances into and out of the cell membrane. The human
body covers about 140 g of cholesterol; over 95% of the cholesterol is within
the cells and cell membranes. To source the cells with cholesterol, which is
lipophilic (fat-soluble)
and hydrophobic (water-repellent when wetted), it is used to transport it via
the blood lipoproteins bound. These can be of different densities and are
divided into chylomicrons, VLDL, IDL, LDL, HDL, and lipoprotein according to
their behavior during centrifugation or electrophoresis.
The numbering of carbon atoms and the designation of the
rings in the steroid structure is also the basis for cholesterol.
In the body, cholesterol serves, among other things, as a
precursor for steroid hormones and bile acids. The cholesterol side chain
separating enzyme converts cholesterol to pregnenolone for the formation of
hormones. This is the starting compound from which the body builds the sex
hormones testosterone, estradiol and progesterone, and adrenal hormones ( corticoids
) such as cortisol and aldosterone. Bile acids such as cholic acid and glycolic
acid are also based on the starting substance cholesterol.
An intermediate product of cholesterol biosynthesis,
7-dehydrocholesterol, is the provitamin for vitamin D formation through UV
light.
New research also shows that the body uses cholesterol for cardiac
glycosides' biosynthesis. The significance of these endogenously synthesized
glycosides is still mostly unknown.
Based on sediment finds with chemical cholesterol relatives
( sterols ), some researchers assume that the cholesterol molecule, if it never
appeared otherwise than in living matter, must be ancient in evolutionary
history. However, the biosynthesis of
the molecule can only function since oxygen has been present in the atmosphere.
For this reason, hardly any cholesterol is found in bacteria and the membranes
of mitochondria; Plants and mushrooms also contain no cholesterol but other,
structurally similar sterols.
No comments:
Post a Comment
Note: only a member of this blog may post a comment.