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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 a syntific name of mopani tree
Sitabi Reply
What is the function of cell
Bello Reply
Wat is the function of cell?
Belbon Reply
What is biology
ct Reply
what is biology
Anyieth Reply
what is the name of the organelle responsible for heredity
Adelokun Reply
What's the main function of the CELL
Victor Reply
what is the main function of the cell
Hope
Is the smallest unit of an living things
Chanda Reply
Okay
Jason
What is a cell
Jason Reply
A cell is the basic unit of life.
Bernard
what is the photosynthesis
Brian Reply
describe cellular event during meiosis
Ruth Reply
what is reproduction
Ruth
reproduction is the process by which living organisms give birth to new offsprings of the same kinds
Bernard
Reproduction is a process by which organisms give rise to new members of their species
Fru
Reproduction is the process whereby living organisms produces the young ones of their own kind to ensure continuity of life
Eunice
is the process by which young offsprings are produced from order ones
Banda
what is chromtograph
Manzoor
what are the example of photosynthesis
Gamshe Reply
Is how plant covert sugar and energy, air and sunlight into energy to grow
Timileyin
An example of photosynthesis is how plants convert sugar and energy from water, air and sunlight into energy to grow.
Bernard
Pls how fertilization occurs in the womb
Rebecca
Pls am asking how does fertilization occurs in the womb
Rebecca
An egg is released in the ovary of a woman during ovulation. in the presence of a sperm this egg cell fuses with the sperm cell to form a zygote ( fertilization) this zygote now moves thru the fallopian tube down to the womb where implantation takes place. the zygote develops thru to a baby
Fru
how are you everyone in here
Brian
what is biology
Odion
My cordial salam to everybody. I have a question to all. What do you mean by plasma membrane?
Mahmud Reply
Plasma membrane or Cell membrane is the outer layer of tissue surrounding the whole or part of an organ. in addition, it is the outer flexible or semi-flexible covering or waterproofing whose primary function is to exclude water.(usually in plants and animals).
Job
I have a question .... Why cell wall is not present in animals cells and why it is present in plants cells?
ShAmy
what is glucose
Sisay
how alkali metal form
Puskal Reply
what is a cytosol
Siddeeqah Reply
cytosol is the internal fluid of the cell and a large part of cell were metabolism occur
Bernard
u are right dear.
Job

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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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