By- Katherine Kauffman
Vanessa Witmer
Brief Steroid Information
 Steroids are the third major class of lipids.
 Their structure is basically four rings.
 It starts with three cyclohexane rings connected
together and ends with a fused cyclopentane ring.
Cyclohexane Cyclohexane
Cholesterol and You
 Cholesterol is the most important steroid in the
human body.
 Most people don’t really even think of cholesterol as
being a steroid.
 The one thing people ‘know’ about cholesterol is that
it’s bad but in actuality it is extremely necessary for
human life.
Cholesterol Functions
 Cholesterol has many functions one of which is to
serve as a plasma membrane component in, for
example, red blood cells.
 Cholesterol is also a raw material for the synthesis of
other steroids.
 Ex- Sex hormones, adrenocorticoid hormones and
bile salts.
Where does Cholesterol come
from?
 Cholesterol is constantly going through your blood
and is in a dynamic state.
 So despite the fact people try and stay away from
cholesterol you can’t really escape from it.
 Your liver is currently making cholesterol that satisfies
your needs even if you aren’t eating anything that
contains cholesterol.
 If cholesterol level goes over 150 mg/100 mL, cholesterol
synthesis in the liver is reduced to half the normal rate
of production.
 Gallstones are basically pure cholesterol.
Lipoproteins
 Cholesterol is hydrophobic as are esters of cholesterol.
 Due to being hydrophobic , cholesterol needs a water-
soluble carrier to go through the blood.
 This carrier is none other then the lipoproteins
 Lipoproteins contain both lipid and protein molecules
and not only transports cholesterol but fat as well.
 There are four different types of lipoproteins
High-density Lipoproteins
 Abbreviated HDL and also called ‘good cholesterol’
 HDL consists of 33% protein and 30% cholesterol
 HDL particles are able to remove cholesterol from
arteries and send it back to the liver.
 A person with high HDL levels is less likely to have
cardiovascular disease while people with lower levels
of HDL are at risk for the disease.
 Women in the pre-stages of
menopause have more HDL then
men.
 This puts women at a lower risk
for coronary heart disease.
Low-density Lipoproteins
 Abbreviated LDL also called ‘bad cholesterol’
 Contains 25% protein and 50% cholesterol
 High levels of type B LDL particles are shown to
increase the risk heart disease and other health
problems.
 Type A LDL particles due the exact opposite.
Very-low-density lipoproteins
 Abbreviated VLDL
 VLDL’s mainly carry triglycerides that are synthesized
by the liver.
 VLDL’s transport not only triglycerides but also
phospholipids, cholesteryl esters and of course
cholesterol.
Chylomicrons
 Chylomicrons carry dietary lipids that are synthesized
in the intestines.
 They consist of 85%-92% triglycerides
 6%-12% phospholipids
 1%-3% cholesterol
 And 1%-2% proteins
 They are produced in the absorptive cells on the small
intestines.
Transportation of Cholesterol From
VLDL to LDL
 When cholesterol is transported from the liver, it starts
as a VLDL particle.
 The VLDL core has triglycerides, cholesteryl esters,
and cholesteryl linoleate.
 The core of VLDL is surrounded by a polar coat of
phosolipids and proteins.
 When capillaries reach muscle of fat, proteins, except
apoB-100, are removed from the VLDL, and the
lipoprotein shrinks and leaves only cholesteryl esters,
turning it into an LDL.
Cholesterol in LDL
 LDL’s carry cholesterol to the cells that have LDL-
receptors that line the cell surface in concentrated
areas (coated pits).
 The LDL proteins bind the LDL
receptors in the coated pits.
 LDL is then taken into the
endocytosis (inside) of the cell and
are broken down by enzymes.
Cholesterol in LDL
 The cholesterol is separated from the cholesteryl esters
and then used as a component of the membrane.
 Cholesterol builds up in blood when the LDL receptors
don’t have the right amount in number.
 Genetics and diet both determine cholesterol levels in
the blood.
How HDL moves cholesterol
 High-density lipoproteins move cholesterol from the
peripheral tissues to the liver and moves the
cholesterol to the LDL.
 Free cholesterols in HDL are turned into cholesteryl
esters when in the serum.
 Bile acids and steroid hormones are synthesized in the
liver from the esterfied cholesterols.
How HDL moves cholesterol
 The HDL sticks to the liver cell surface and moves the
cholesterol ester to the cell in a selective lipid uptake.
 The HDL reenters the circulation after it has been
taken from the lipid content.
 You want high HDL levels in the blood because it
removes cholesterol from the blood stream.
Levels of LDL and HDL
 Cholesterol is insoluble in water
 When cholesterol is high, plaque deposits form on the
inner surfaces of the arteries and can slow blood flow
(atherosclerosis)
 Atherosclerosis and high blood pressure leads to heart
attack, stroke, or malfunctioning kidneys
Levels of LDL and HDL
 Myocardial infarction- the death of a heart muscle
because of lack of oxygen
 Cholesterol is usually transported in low-density
lipoproteins
 When the concentration of cholesterol in a cell is low,
the synthesis of LDL receptors increases
Levels of LDL and HDL
 Familial hypercholesterolemia is a disease where the
cholesterol level in the plasma is 680 mg/100 mL,
which is unlike normal levels.
 The normal level is 175 mg/100 mL.
 When a person has a high LDL level and a low HDL
level it means that there was a faulty cholesterol
transport and are at risk for atherosclerosis.
 It is best to have high HDL levels and low LDL levels in
the bloodstream.
Serum Cholesterol Levels
 The amount of cholesterol synthesized in the liver is
determined by the serum cholesterol level.
 Synthesize of cholesterol is low when the serum
cholesterol level is high.
 Synthesize of cholesterol is high when the serum
cholesterol level is low.
 A low cholesterol diet can lower the serum cholesterol
level and some drugs can inhibit the synthesis of
cholesterol.
LDL Drugs
 Statin drugs block the synthesis of cholesterol in cells
which leads to the synthesis of LDL receptor proteins.
 Example of some statin drugs- Lipitor and Zocor
 The more LDL in the cells the lower amount of
cholesterol in the arteries.