What is cholesterol – Science Explained

Cholesterol has been cited many times as one of the most important small molecule in biology, and especially in cell function. It was first isolated in the 18^th century, however, it was initially a tricky molecule to work with, and took until the 20^th century before specific insight was gained on its structure and action. It wasn’t until the 60’s, that cholesterol was first synthesised, by Robert.B.Woodward, who earned the Nobel Prize in chemistry for his efforts.

Cholesterol, like many organic compounds present in the body, is a complex organic molecule, and primarily holds its importance as a constituent of cell membranes. It is classed in the subgroup of steroids, and is the major sterol synthesised by animals. Structurally it is formed with rigid carbon rings, and a hydrocarbon tail. Its composition is such that it is a lipid, and is so hydrophobic, apart from a hydroxyl at one end, making it amphipathic. Cholesterol is synthesised from acetic acid, by using enzymes, which are crucial in selectively speeding up chemical reactions in the body.

 Its role in cell membranes sees it placed adjacent to the tails of phospholipids, and the hydroxyl group forms hydrogen bonds with phospholipids, preventing the close packing in the spaces in between of fatty acids. Cholesterol therefore prevents the transition to the crystalline phase at body temperature – crucial for cell mobility and survival.

Cholesterol is also important for digestion. Bile acids, are a broken down polar form of cholesterol, which are generated from cholesterol in the liver, and subsequently secreted into the gall bladder, and eventually pass into the intestine and play their role in the breaking down of fats. This is the only method of cholesterol excretion in the body, and most is reabsorbed in the small intestine, to be eventually re-secreted again by the liver (enterohepatic cycle).

Cholesterol serves a number of other important functions, including its role in the synthesis of Vitamin D3, steroid hormones (processed in the adrenal gland) and sex hormones. They are therefore important in stress regulation due to the production of these hormones.

Aside from its importance, Cholesterol can also cause problems in the body. Too much LDL (Low Density Lipoprotein) can cause thickening of the arteries over time, causing heart problems. Cholesterol is also known to crystallise in the gall bladder, causing gallstones. The links to heart disease give cholesterol a bad press, but it is important to note its significance and role in healthy cell production.