This document discusses cholesterol, including what it is, where it comes from, its functions, and importance in the body. Cholesterol is a lipid found in cell membranes and transported in the blood. It is synthesized in the body and absorbed from dietary sources like eggs. Cholesterol performs essential functions like making cell membranes and producing hormones. It is needed for brain and nerve function and plays an important role in many vital bodily processes. Too much cholesterol can accumulate in arteries and lead to health issues, but it also has protective functions and is necessary for overall health.

1. BIOCHEMISTRY II
BY HIJAB SIDDIQI

2. CLINICAL IMPORTANCE OF
CHOLESTEROL

3. WHAT IS CHOLESTEROL?
 Cholesterol is a lipidic, waxy alcohol found in the cell
membranes and transported in the blood plasma of all
animals.
 It is an essential component of mammalian cell membranes
where it is required to establish proper membrane
permeability and fluidity.
 Cholesterol is the principal sterol synthesized by animals,
but small quantities are synthesized in other eukaryotes,
such as plants and fungi. It is almost completely absent
among prokaryotes.
 Cholesterol is classified as a sterol (a contraction of steroid
and alcohol).

4. WHERE DOES IT COME FROM?
 Most of the cholesterol in the body is synthesized therein;
some is absorbed in the diet
 Cholesterol is primarily synthesized from acetyl CoA through
the HMG-CoA reductase pathway in many cells and tissues.
About 20–25% of total daily production (~1 g/day) occurs in
the liver; other sites of high synthesis rates include the
intestines, adrenal glands, and reproductive organs.
 Major dietary sources of cholesterol include cheese, egg
yolks, beef, pork, poultry, and shrimp.

6. FUNCTIONS
Cholesterol performs three main functions:
 It helps make the outer coating of cells.
 It makes up the bile acids that work to digest food
in the intestine.
 It allows the body to make Vitamin D and
hormones, like estrogen in women and
testosterone in men.
Without cholesterol, none of these functions would
take place, and without these functions, human
beings wouldn't exist.

7. OTHER FUNCTIONS
 It is an important component of cell membranes.
 In the central nervous system it exerts an insulating effect
due to its high dielectric constant.
 Being an alcohol, cholesterol forms esters with fatty acids
for which it acts as a special transport.
 Cholesterol is a constituent of plasma lipoproteins, the
richest being LDL.

9. IMPORTANCE IN OUR BODY
 Cholesterol is an important component of the cell membranes,
including organelle membranes inside the cell. (The body
contains billions of cells.)
 The right proportion of phospholipids, fatty acids and
cholesterol in cell membranes allows them to be flexible while
still holding their shape.
 “Cholesterol is used by the body as raw material for the healing
process. This is the reason the injured areas in the arteries (as
in atherosclerosis)… have cholesterol along with several other
components (such as calcium and collagen) in the “scar” tissue
that is formed to heal the “wound”.
 Cholesterol is found in large amounts in brain tissue where it is
needed for normal brain function. Research has shown that
cholesterol in eggs is helpful to older people whose memory is
declining.

10. CONT…
 Cholesterol often elevates as part of a protective immune
system response to chronic infection.
 Infants need plenty of cholesterol for proper brain
development and cholesterol is normally found in large
amounts in human breast milk. (Infant formulas usually
contain little to no cholesterol because of the widespread lack
of understanding about cholesterol.)
 Adrenal and gonadal hormones are made from cholesterol.
These are the stress handling, energy producing and
reproductive hormones. (This is why serum cholesterol
normally elevates with excessive or prolonged stress.)
 Cholesterol is vital for proper nerve function. Three quarters
of the myelin membrane is made from fat and of that nearly
one quarter is cholesterol.

11. CONT…
 Vitamin D is made from cholesterol in the skin.
 Cholesterol is converted into bile salts in the liver which are
needed to break down and emulsify fats.
 Cholesterol is needed in large amounts in the skin where it
is vital for skin health and strength.
 Although lowering serum cholesterol does seem to
decrease deaths from heart disease, it “does not, in the
least, improve overall mortality rates. People who achieved
the lowest cholesterol levels – 160 units or less – had
unexpectedly higher rates of death from other causes, such
as liver cancer, stroke, lung disease, alcoholism and suicide

13. WHEN GOOD FATS GO BAD
 When there's too much cholesterol in the blood, it collects on the
inside linings of blood vessels, similar to the way grease and fats
poured down the sink collect inside drain pipes. When plaques of
cholesterol form inside arteries, it's known as atherosclerosis or
"hardening of the arteries," which can lead to strokes and heart
disease.
 The main culprit in this dangerous process is cholesterol that's
packaged into lipoproteins that are less dense with protein and
have more fats. These low-density lipoproteins, are the "bad"
cholesterol that collects in plaques on artery walls.
 There's a hero in this tale, though -- and it's also cholesterol.
More specifically, cholesterol that's packaged by the liver into
lipoproteins that are dense with proteins and have less fat. These
high-density lipoproteins, or HDL, are the "good" cholesterol.
What's good about HDL is the way it seems to remove plaques of
LDL inside arteries, "cleaning" the arteries as it moves through

15. IN SHORT….
Cholesterol is vital to the healthy function of your
body, actually core to survival. You want good
levels of HDL and LDL because you are healthy,
not because you have drugged them to look better
on paper. The idea of cholesterol fitness, like
physical fitness, is a proper way to look at this
issue.

16. THANK YOU !