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The molecular structures of alpha-linolenic acid, an omega-3 fatty acid is shown. Alpha-linolenic acid has three double bonds located eight, eleven, and fourteen residues from the acetyl group. It has a hooked shape.
Alpha-linolenic acid is an example of an omega-3 fatty acid. It has three cis double bonds and, as a result, a curved shape. For clarity, the carbons are not shown. Each singly bonded carbon has two hydrogens associated with it, also not shown.

The farthest carbon away from the carboxyl group is numbered as the omega ( ω ) carbon, and if the double bond is between the third and fourth carbon from that end, it is known as an omega-3 fatty acid. Nutritionally important because the body does not make them, omega-3 fatty acids include alpha-linoleic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), all of which are polyunsaturated. Salmon, trout, and tuna are good sources of omega-3 fatty acids. Research indicates that omega-3 fatty acids reduce the risk of sudden death from heart attacks, reduce triglycerides in the blood, lower blood pressure, and prevent thrombosis by inhibiting blood clotting. They also reduce inflammation, and may help reduce the risk of some cancers in animals.

Like carbohydrates, fats have received a lot of bad publicity. It is true that eating an excess of fried foods and other “fatty” foods leads to weight gain. However, fats do have important functions. Many vitamins are fat soluble, and fats serve as a long-term storage form of fatty acids: a source of energy. They also provide insulation for the body. Therefore, “healthy” fats in moderate amounts should be consumed on a regular basis.

Waxes

Wax covers the feathers of some aquatic birds and the leaf surfaces of some plants. Because of the hydrophobic nature of waxes, they prevent water from sticking on the surface ( [link] ). Waxes are made up of long fatty acid chains esterified to long-chain alcohols.

The photo shows leaves on a plant; the leaves appear thick, shiny, and waxy.
Waxy coverings on some leaves are made of lipids. (credit: Roger Griffith)

Phospholipids

Phospholipids are major constituents of the plasma membrane, the outermost layer of animal cells. Like fats, they are composed of fatty acid chains attached to a glycerol or sphingosine backbone. Instead of three fatty acids attached as in triglycerides, however, there are two fatty acids forming diacylglycerol, and the third carbon of the glycerol backbone is occupied by a modified phosphate group ( [link] ). A phosphate group alone attached to a diaglycerol does not qualify as a phospholipid; it is phosphatidate (diacylglycerol 3-phosphate), the precursor of phospholipids. The phosphate group is modified by an alcohol. Phosphatidylcholine and phosphatidylserine are two important phospholipids that are found in plasma membranes.

The molecular structure of a phospholipid is shown. It consists of two fatty acids attached to the first and second carbons in glycerol, and a phosphate group attached to the third position. The phosphate group may be further modified by addition of another molecule to one of its oxygens. Two molecules that may modify the phosphate group, choline and serine, are shown. Choline consists of a two-carbon chain with a hydroxy group attached to one end and a nitrogen attached to the other. The nitrogen, in turn, has three methyl groups attached to it and has a charge of plus one. Serine consists of a two-carbon chain with a hydroxyl group attached to one end. An amino group and a carboxyl group are attached to the other end.
A phospholipid is a molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone. The phosphate may be modified by the addition of charged or polar chemical groups. Two chemical groups that may modify the phosphate, choline and serine, are shown here. Both choline and serine attach to the phosphate group at the position labeled R via the hydroxyl group indicated in green.

A phospholipid is an amphipathic molecule, meaning it has a hydrophobic and a hydrophilic part. The fatty acid chains are hydrophobic and cannot interact with water, whereas the phosphate-containing group is hydrophilic and interacts with water ( [link] ).

Questions & Answers

what is photosynthesis
Victor Reply
The process plants use to convert sunlight into food (energy).
juanita
Some other organisms use
juanita
types of photosynthesis
Victor
ps1 and ps2
smritilekha
what is used to determine phylogeny?
Israel Reply
which condition is the basis for a species to be reproductively isolated from other members?
Israel Reply
Why do scientists consider vestigial structures evidence for evolution?
Israel
8.Which statement about analogies is correct?
Israel
What is true about organisms that are a part of the same clade?
Israel
Why is it so important for scientists to distinguish between homologous and analogous characteristics before building phylogenetic trees?
Israel
(CH2O)n is the stoichiometric formula of
Marcellus Reply
what are nucleotide
Anastijjaninaiya Reply
Methane,ammonia,water and sugar are dissolved to form nuceotide
Me
Introduction To Biology
Tanveer Reply
can ringworm be caused by bacterium
fred Reply
Nope
ejikeme
Branches of biology
Tanveer
no it does not occurs by bacterium
gopal
what is a brick?
Istifanus Reply
what is gene in biology?
yousaf Reply
it is a heredity unit
Me
what is DNA
yousaf Reply
carrier of genetic information
missy
deoxyribonucleic acid
gopal
it contains genetic information and brings it to one generation to other
gopal
it is of two Types circular DNA and linear DNA
gopal
plasmids are the type of small circular DNA which lies outside the genomic DNA
gopal
And what makes a virus to be difficult to destroy
Mosongo
what observation is made when dry seeds and soaked seeds are put in a vacuum flask
Robin Reply
there is respiration from the soak seeds which shows on the walls of the vacuum flask
Israel
what's mammals ?
Istifanus Reply
mammals are vertebrates ,any member group of vertebrates animals in which the young are nourished with milk from special mammary glands of the mother.
yousaf
what are actin and myosin
Praveen Reply
they are muscle filaments
Israel
they make up the microfibrils of the muscle ,relaxing and contracting to cause movement
Israel
Please did anybody know the questions that will come out in the coming practical?
Oladimeji
Why it is importantthat there are different types of protein in plasma membraine for the transport materials into and out of a cell?
Louellie Reply
the nerve cell
Mustapha Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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