Oracle IAS, the best coaching institute for UPSC/IAS/PCS preparation in Dehradun brings to you UKPCS Science Chemistry (paper 6)
It is a sterol (or modified steroid), a type of lipid molecule, and is biosynthesized by all animal cells, because it is an essential structural component of all animal cell membranes.
Function: Essential to maintain both membrane structural integrity and fluidity. Cholesterol enables animal cells to dispense with a cell wall (to protect membrane integrity and cell viability), thereby allowing animal cells to change shape rapidly and animals to move (unlike bacteria and plant cells, which are restricted by their cell walls).
In addition to its importance for animal cell structure, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid, and vitamin D. Cholesterol is the principal sterol synthesized by all animals.
Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling and nerve conduction.
The liver excretes cholesterol into biliary fluids, which is then stored in the gallbladder. Bile contains bile salts, which solubilize fats in the digestive tract and aid in the intestinal absorption of fat molecules as well as the fat-soluble vitamins, A, D, E, and K.
Good vs bad:
According to the lipid hypothesis, since cholesterol (like all fat molecules) is transported around the body (in the water outside cells) inside lipoprotein particles, elevated cholesterol concentrations (hypercholesterolemia) — potentially offers a lower cost way to estimate concentrations of LDL particles; possibly even low concentrations of functional HDL particles — both variations strongly associated with cardiovascular disease because LDL particles promote atheroma development in arteries (atherosclerosis).
This atherosclerotic disease process, over decades, leads to myocardial infarction (heart attack), stroke, and peripheral vascular disease. Since higher blood LDL, especially higher LDL particle concentrations and smaller LDL particle size, contribute to this process more than the cholesterol content of the HDL particles, LDL particles are often termed “bad cholesterol” because they have been linked to atheroma formation. On the other hand, high concentrations of functional HDL, which can remove cholesterol from cells and atheroma, offer protection and are sometimes referred to as “good cholesterol“. These balances are mostly genetically determined, but can be changed by body build, medications, food choices, and other factors.
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