University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

468

Pages:

6
Author:

Sheha A.

Bile Acids Bile acids are synthesized in the liver. 24 carbon chain steroids 2 or 3 hydroxyl groups on the steroid backbone. These groups are amphipathic in nature since they possess both polar and non polar groups. These serve as emulsifiers and act as detergents in the intestine and aid in the digestion and absorption of lipids. 1. Synthesis of bile acids The step catalyzed by 7-alpha-hydroxylase is inhibited by bile acids and this regulates the synthesis of bile acids. Cholic acid and chenodeoxycholic acid are the primary bile acids. Primary bile acids: cholic acid and chenodeoxycholic acid. Secondary bile acids: deoxycholic acid and lithocholic acid (deconjugation of primary bile acids). In the intestine: A portion of primary bile acids undergoes deconjugation and dehydroxylation to form secondary bile acids. These reactions are catalyzed by bacterial enzymes in the intestine. Bottom: Cholesterol | | | 7-α-hydroxylase | | | 7-α-hydroxycholesterol | | |------|------| | cholic acid | chenodeoxycholic acid | | | | | | | | glyco- | tauro- | glyco- | tauro- | | cholic | cholic | chenodeoxy | chenodeoxy | | acid | acid | cholic | cholic | | | | acid | acid | d) Androgens (e.g., testosterone) e) Estrogens (e.g., estradiol) Cholesterol (C27) Progesterone (C21) Progesterone (C21) | | | |---------|---------| | Cortisol | Estradiol | | (C21) | (C18) | **3. Synthesis of vitamin D** 7-dehydrocholesterol, an intermediate in the synthesis of cholesterol, is converted (vitamin D3) by ultraviolet rays in the skin.