When Is Maryland Senior Week Yahoo

chemistry of steroids: cholesterol in the life cycle of eukaryotes and prokaryotes

Cholesterol is an essential ingredient of the cell membrane of all animal cells:

- is inserted between two layers of phospholipids oriented with the-OH groups close to the polar heads of phospholipids, thus decreasing the fluidity of the mosaic (see fluid mosaic model) but increasing the mechanical stability and flexibility of the cells. In doing so, however, decreases the permeability to small water-soluble cell.

- Together with protein molecules cholesterol regulates the exchange of messenger substances through the cell membrane.

- Growth and cell division are not possible without cholesterol.

- Cholesterol is the basic substance for the synthesis of steroid hormones such as aldosterone, cortisone, testosterone, estradiol, etc.. (See adrenal glands and vitamin D).

- The cholesterol produced in the liver is used largely for the production of bile, a substance secreted into the duodenum, which serves to emulsify dietary lipids to make it absorbable by the small intestine.

Di Massimo Capobianco