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Essential Fatty Acids and Phospholipids

Essential fatty
acids & phospholipids are primary constituents of cell
membranes, and as such they are vital to the makeup of the human
body. Essential fatty acids are used to generate certain
intra-cellular hormone-like substances, including prostaglandins
and leukotrienes, which are responsible for regulating key
bodily processes. Source Naturals essential fatty acid
supplements are potent, effective and chemical-free. Click here for Essential Fatty Acids products ---------------------------------------------------
----------------------------- LIPIDS, CELL MEMBRANES &
EICOSANOIDS Almost by definition, life is composed of
cells, and cells are defined by membranes. One theory suggests
that, around four billion years ago, self-replicating molecules,
similar to the ribonucleic acid or RNA in our own cells, were
synthesized from organic molecules. These self-replicating
molecules adapted to changes in their environment to increase
their potential for survival. Thus began the process of
evolution that has led, over the eons, to us. One turning point
was when these molecules developed membranes - envelopes which
could help concentrate chemicals needed for the cell's survival.
There existed in the "primordial soup" substances uniquely
suited to this purpose: a class of organic compounds we call
lipids . Lipids are more commonly called fats, and in this
health and image-conscious age people often think of them as
something to be avoided. However, the word fat refers to a
variety of substances with a diverse range of chemical
properties, which are essential for survival and well-being .
The simplest lipids, fatty acids such as palmitic acid, consist
of a hydrocarbon "tail" connected to a carboxyl group (COOH).
The majority of lipids in food and in the human body occur in
the form of triglycerides - a molecular configuration in which
three fatty acid chains are attached to a 'backbone' of glycerol
(an organic alcohol composed of a 3-carbon chain with an alcohol
group attached to each carbon). The major roles of lipids can be
described as energy and storage, structural, and
metabolic. Energy and Storage Molecules can contain
more or less chemical energy. In living systems most of the
energy needed to drive chemical reactions is derived from
oxidation. Oxygen, the ultimate electron acceptor, is a strong
oxidant: it has a marked tendency to attract electrons, becoming
reduced in the process. When a molecule undergoes a chemical
reaction from a high-energy reduced state to a low-energy
oxidized state, energy is released. This is what happens in a
fire: the high-energy carbohydrates in wood, such as glucose,
react with oxygen, releasing heat and the low-energy molecules
of carbon dioxide and water. This is similar to what happens in
metabolism. Most of the carbon in a fatty acid chain is
highly reduced, which makes fats more energy-rich than the other
organic molecules that can be burned as food. This is what we
mean when we say fats are high in calories - a measure of the
amount of energy released when a substance is oxidized. Fats
contain more than twice as many calories as carbohydrates. This
makes fats an important storage fuel for most of the
body. Structure Another important class of lipids in
the human body consists of the phospholipids. Like
triglycerides, phospholipids contain fatty acid chains- in this
case two, one saturated and one unsaturated, attached to a
glycerol backbone. Unlike triglycerides, in phospholipids the
third carbon of the glycerol molecule is attached to a phosphate
(a molecular group that contains phosphorus and oxygen), which
is in turn attached to either an amino acid or, in the case of
phosphatidyl choline, a molecule of the B-vitamin - like
substance, choline. Their unique molecular structure
makes phospholipids amphipathic, which means 'likes
both': The phosphate-containing head group is strongly
dipolar (it has positive and negative charges and can mix with
water, and thus is hydrophilic, which means
'water-loving'). The two fatty acid chains make up a long
tail group which is nonpolar (it has no charge and cannot mix
with water, and thus is hydrophobic, which means
'water-hating'). Fats, being hydrophobic, tend to separate
out from water. When fat is mixed with phospholipids in the
presence of water, the phospholipid molecules attach themselves
to the molecules of fat and bring them into the water solution,
enabling the fats to dissolve in water. Phospholipids
form a structure called a lipid bilayer, a two-ply sheet of
phospholipid molecules in which the hydrophilic head groups face
outward and are in contact with the water, and the hydrophobic
tails face each other on the inside of the bilayer. This
structure is one of the key constituents of the cell membranes
that surround every living cell. The lipid bilayer of
cell membranes is a fluid in which membrane-embedded proteins
"float." These proteins serve a wide variety of different
functions. Some are enzymes, serving to carry out chemical
reactions in the adjacent solution. Some are involved in
signaling, in which a biochemical action in a cell is
'commanded' by means of a hormone or some such other signaling
molecule. Still others are involved in transporting substances
across the membrane, into or out of the cell. The
functions of membrane-embedded proteins are dependent on a very
precise balance of phospholipids for their function.
Phosphatidyl serine, for instance, has a negatively-charged head
group that associates preferentially with a class of
membrane-bound proteins called ATPases. ATPases regulate, among
other things, the balance of sodium and potassium in intra- and
extracellular fluids, a balance that is necessary for the
integrity of our cells and also for the electrochemical impulses
that make up our thoughts and feelings. Without phosphatidyl
serine, these vitally important membrane-embedded proteins could
not function. Cholesterol is a waxy substance that is
essential to the structure of cell membranes, which depend for
their function on a delicate balance between fluidity and
solidity. Cholesterol provides a semifluid matrix, as well as
enhancing membrane fluidity. About 80% of the cholesterol the
body uses is manufactured by the liver; the other 20% is
consumed in food. Elevated blood cholesterol levels are
associated with heart disease. Saturated fats are converted into
cholesterol more readily than unsaturated fats, and
polyunsaturated fats usually depress blood cholesterol
concentration to some degree. Researchers have thus recommended
that people lower their consumption of saturated fats and
increase their consumption of polyunsaturated fats. A process
called hydrogenation , in which hydrogen molecules are added, is
used to harden these unsaturated fats to create solid spreads,
such as margarine. This process causes formation of altered fats
called trans fatty acids. Although the results are not
conclusive, human and animal studies have pointed to possible
deleterious effects from consumption of trans - fatty acids,
which are estimated to account for 5.5% of all fats consumed by
Americans. These studies include one in men and women that
showed harmful effects of trans - fatty acids on blood
cholesterol ratios. Metabolic When each link of a
fatty acid chain contains an atom of hydrogen, as in palmitic
acid, that fatty acid is said to be saturated . If two carbon
links are double bonded to each other, each has one less
hydrogen atom, and the fatty acid chain is said to be
unsaturated. If a fatty acid contains one double bond, it is
said to be monounsaturated, and if it has two or more double
bonds it is said to be polyunsaturated . Certain polyunsaturated
fatty acids cannot be manufactured by the body and must be
obtained from the diet. These nutrients are called essential
fatty acids and are necessary for the normal function of all
tissues. The essential fatty acids fall into two
categories: (1) Those with an unsaturated double bond
between the 6th and 7th carbon in the chain, called omega-6
fatty acids, which include linoleic acid (LA), gamma-linolenic
acid (GLA), and arachidonic acid (AA). (2) Those with a
double bond between the 3rd and 4th carbons, called omega-3
fatty acids, which include alpha-linolenic acid (ALA),
eicosapentaenoic acid (EPA), and docosahexaenoic acid
(DHA). In addition to being phospholipid precursors,
essential fatty acids can be converted to a class of hormone
like intracellular messengers called eicosanoids. The
physiologic effects of eicosanoids are potent in minute
quantities. Their effects are so powerful that they need to be
produced near the site of their action and are quickly
inactivated. The important eicosanoids include the thromboxanes,
leukotrienes and prostaglandins (PGs ). Prostaglandin molecules
consist of a five-carbon ring with two side chains. They can be
distinguished from each other by numbers that refer to the
number of double bonds in their molecular side chains: 1-series
PGs have one double bond, 2-series have two double bonds, and so
on. Prostaglandins mediate a variety of bodily processes,
including inflammatory reactions, blood vessel contraction and
dilation, and platelet aggregation. The different PGs have
different effects on the body, and different essential fatty
acids act as precursors for different PGs. Important
essential fatty acids in humans are the omega-6 fatty acids,
which include linoleic acid (LA), gamma-linolenic acid (GLA),
and arachidonic acid (AA). 1-series PGs are derived from GLA and
tend to cause blood vessels to dilate and reduce the stickiness
of platelets (cell fragments in the blood that help initiate
blood clotting). 2-series PGs are derived from arachidonic acid
and tend to increase platelet stickiness and cause blood vessels
to constrict. Meat and dairy products are dietary sources of the
PG2 precursor, arachidonic acid; American diets tend to be rich
in these foods. The rate-limiting step for production of GLA in
the human body is an enzyme called delta-6-desaturase (D6D). The
action of this important enzyme can be blocked by a number of
different lifestyle factors, including a diet high in saturated
or trans- fatty acids and chronic alcohol consumption. A modest
increase in consumption of GLA will significantly increase the
ratio of GLA to AA in the tissues, which may have a beneficial
effect on the homeostasis of the cardiovascular system.
Supplementation with omega-3 fatty acids, such as flaxseed oil
or fish oil, is beneficial for similar reasons. Omega-3 fatty
acids are precursors for 3-series PGs, which reduce platelet
stickiness. Series-3 PGs also tend to inhibit conversion of AA
into its metabolites, the 2-series PGs. The lipid
composition of our diets has changed radically in the 20th
century. Our intake of saturated fats has increased
dramatically, and trans fatty acids, which did not exist before
the advent of modern food processing technology, now form a
major part of our diets. We eat less fish and green leafy
vegetables, important sources of omega-3 fatty acids, than our
ancestors did. Far from being an inert, homogeneous substance,
fat is dynamic and varied - a subtle and interactive matrix for
many of the biological processes taking place in our bodies,
minute by minute.




Essential, Fatty, Acids, and,