Question

1. What are the different functions of Sterols? What are some of the different molecules that are made from cholesterol as a precursor?

Answer 1

What are the different functions of Sterols?

ans:

Both sterols and sphingolipids play important structural roles in many cellular membranes. Sterols have been shown to influence fluidity and permeability of membranes, both in vitro and in vivo . Still, at least some eukaryotic cells, like cultured insect cells, can function without almost any sterol in their membranes and it has been proposed that sphingolipids with dien-sphingoid bases can replace sterols in the membrane . Certain glycosphingolipids have also been proposed to serve a structural role, for example in the chilling response of plants . Another very important role of sterols that has to be kept in mind when studying their cellular functions is the production of different signaling molecules. Multicellular organisms rely on sterol-derived hormones like the steroids of vertebrates, brassinosteroids of plants and ecdysteroids, or other molting hormones of invertebrates. Other sterol-derived signaling molecules include Vitamin D, bile acids, and oxysterols

Sterols are ringed lipids that play a role in the membrane integrity of eukaryotes. Apicomplexa lack the ability to synthesize sterols so must obtain them from other organisms, most commonly their host. Phototrophs such as dinoflagellates possess genes to synthesize sterols inside the cell. Sterol composition is closely connected to phylogenetic organization, allowing

What are some of the different molecules that are made from cholesterol as a precursor?

ans:

Within cells, cholesterol is also a precursor molecule for several biochemical pathways. For example, it is the precursor molecule for the synthesis of vitamin D in the calcium metabolism and all steroid hormones, including the adrenal gland hormones cortisol and aldosterone, as well as the sex hormones progesterone, estrogens, and testosterone, and their derivatives.

Cholesterol has been isolated from a number of higher plants and its possible importance as a precursor in the formation of other steroids is suggested Formation of cholesterol does not require an alkylation at C-24 and the biosynthetic branch point is therefore quite far removed from the more common phytosterols.

Cholesterol, given that it composes about 30% of all animal cell membranes, is required to build and maintain membranes and modulates membrane fluidity over the range of physiological temperatures. The hydroxyl group of each cholesterol molecule interacts with water molecules surrounding the membrane, as do the polar heads of the membrane phospholipids and sphingolipids, while the bulky steroid and the hydrocarbon chain are embedded in the membrane, alongside the nonpolar fatty-acid chain of the other lipids.

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