This document summarizes cholesterol, including its structure, functions, sources, and regulation. Cholesterol is a sterol present in animal tissues and transported in the blood. It has four fused carbon rings with an eight-carbon side chain and performs essential functions like forming cell membranes and acting as a precursor for bile acids, hormones, and vitamin D. Cholesterol comes from both diet and synthesis in the body, mainly the liver and intestine, and high levels can indicate medical conditions like diabetes or familial hypercholesterolemia.

1. CHOLESTEROL
SYNTHESIS- STEPS
AND REGULATION
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2. CHOLESTEROL INTRODUCTION
 Cholesterol is the major sterol in the animal tissues.
 Cholesterol is present in tissues and in plasma either
as free cholesterol or as a storage form, combined
with a long­chain fatty acid as cholesterol ester.
 In plasma, both forms are transported in protein
steins
 Plasma low­density lipo protein (LDL) is the vehicle
of uptake of cholesterol and cholesterol ester into
many tissues.
Free cholesterol is removed from tissues by plasma
high­density lipo protein (HDL) and transported to the
liver, where it is eliminated from the body either
unchanged or after conversion to bile acids in the
process known as reverse cholesterol transport.

3. VAP (Vertical Auto Profile)
The VAP Test uses the most advanced technology that
provides the most accurate picture of an individual’s
potential for heart disease and diabetes. This information is a
great tool for your physician to provide the proper steps in
preventing future heart attacks. The VAP Test provides a
detailed report of individual lipoprotein subclasses and
Apolipoprotein subclasses. This test not only includes the basic
cholesterol tests, but also identifies any cholesterol
abnormalities that can be a precursor to heart
Disease or diabetes. This is not a fasting blood test; this gives
you flexibility on different appointment times, not just
early in the day.

4. STRUCTURE OF CHOLESTEROL
 The structure of cholesterol consists of four fused
rings (The rings in steroids are denoted by the
letters A, B, C, and D.), with the carbons numbered
in the sequence, and an eight numbered, and
branched hydrocarbon chain attached to the D ring.
 Cholesterol contains two angular methyl groups: the
C­19 methyl group is attached to C­10, and the C­18
methyl group is attached to C­13.
 The C­18 and C­19 methyl groups of cholesterol lie
above the plane containing the four rings.

5. STRUCTURE OF CHOLESTEROL
Steroids with 8 to 10 carbon atoms in the side chain
and an alcohol hydroxyl group at C­3 are classified as
sterols. Much of the plasma cholesterol is in the
esterified form (with a fatty acid attached at carbon
3), which makes the structure even more
hydrophobic.

6. FUNCTIONS OF CHOLESTEROL
Cholesterol is the most abundant sterol in humans and
performs a number of essential functions. For example­
 It is a major constituent of the plasma membrane and of
plasma lipoproteins.
 It is a precursor of bile salts,
 It is a precursor of steroid hormones that include adreno
cortical hormones, sex hormones, placental hormones etc
 Also a precursor of vitamin D, cardiac glycosides,
Sitosterol of the plant kingdom, and some alkaloids.
 It is required for the nerve transmission. Cholesterol is
widely distributed in all cells of the body but particularly
abundant in nervous tissue.

7. SOURCES OF CHOLESTEROL
Cholesterol is derived from
 diet
 synthesis and from the hydrolysis of cholesterol
esters.
 A little more than half the cholesterol of the body
arises by synthesis (about 700 mg/d), and the
remainder is provided by the average diet.
 The liver and intestine account for approximately
10% each of total synthesis in humans.
 Virtually all tissues containing nucleated cells are
capable of cholesterol synthesis, which occurs in the
endo plasmic reticulum and the cytolysis

8. VARIATION OF SERUM
CHOLESTEROL LEVELS
 The normal serum cholesterol concentration ranges
between 150­ 220 mg/dl
High cholesterol concentration is found in­
 Diabetes mellitus
 Nephrotic syndrome
 Obstructive jaundice
 Familial hyper cholesterolemia
 Biliary cirrhosis
 Hypothyroidism

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