To Estimate the Amount of Total
Cholesterol in Serum^23
23.1 Theory
Cholesterol is a solid alcohol found exclusively in animals and contains 27 carbon
atoms (C 27 H 46 O). It possesses a ring structure called
cyclopentanoperhydrophenanthrene. It is a major component of biological
membranes and lipoproteins and amphipathic in nature. It is a precursor in many
metabolic pathways including synthesis of vitamin D, steroid hormones, and bile
acids. About 400–700 mg of cholesterol present in the gut is contributed by biliary
secretion and the turnover of mucosal cells. The cholesterol present in the intestine is
the unesterified form. This form is solubilized by the formation of mixed micelles
that contain the unesterified cholesterol, fatty acids, monoglycerides, phospholipids,
and conjugated bile acids. Maximum absorption of cholesterol occurs in small
intestine. Once absorbed into the mucosal cells, cholesterol along with triglycerides,
phospholipids, and a number of specific apoproteins is reassembled into a large
micelle called chylomicrons. Chylomicrons enter the lymphatics, which empty into
the thoracic duct and eventually enter the systemic venous circulation. Total choles-
terol contains free cholesterol and esterified cholesterol in the ratio 1:3.
#Springer Nature Singapore Pte Ltd. 2018
V. Kumar, K. D. Gill,Basic Concepts in Clinical Biochemistry: A Practical Guide,
https://doi.org/10.1007/978-981-10-8186-6_23
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