Fatty acids (FAs) are organic monocarboxylic acids. Their molecule always begins with a
methyl group (-CH3) and is terminated with a carboxylic one (-COOH). In-between there are
at least 6 methylene groups (-CH2-) and may contain one or more double bonds (-CH=CH-).
Carboxylic acids with a lower carbon atom number than 8 are not considered as fatty
Fatty acids (FA)
are organic monocarboxylic acids. Their molecule always begins with
a methyl group (-CH3) and is terminated with a carboxylic one (-COOH).
In-between there are at least 6 methylene groups (-CH2-) and may contain
one or more double bonds (-CH=CH-). Carboxylic acids with a lower carbon
atom number than 8 are not considered as fatty acids.
The basic characteristics of fatty acids (FA)
The basic characteristics of fatty acids (FA), which determine their
physical, chemical und biological properties, are:
Extraordinary biological properties: Omega 3 and 6
Organisms synthesize FA in specialized cells; there are however
certain fatty acids that cannot be synthesized and the only source for
organisms to obtain them is through a nutrition. FA play two major roles
for the animals:
Energetic - energy storage and energy release
synthesis of vital substances
Organisms synthesize FA as a way to store energy at the time of energy
surplus. FA cover for example in the case of mammals 30% of total energy
demand when the muscle is relaxed, which increases up to 90% at muscle
contraction. Not all cells are however capable to use FAs as an energy
source – the brain cells for instance depend completely on carbohydrates
(glucose to be more precise).
Organisms store energy in the form of triglycerides
– molecules consisting of one glycerol and three fatty acid molecules.
Triglycerides contain about 6 times as much energy as carbohydrates of
the same weight. When organisms need energy they have to break down the
triglycerides enzymatically into glycerol and unbound fatty acids. Free
FA are consequently oxidized in three steps, which finally lead to the
formation of ATP (adenosintriphosphate) - the cells’ primary energy source.
For living organisms the FA are precursors of phospholipids synthesis
(fats which are main constituents of cell membranes), as well as components
of the myelin sheath of the nerve cells and precursors for the synthesis
of hormone-like substances, which serve a number of functions relating
to immunity, activity of the central nervous system, organism reaction
to injuries etc.
Utilization of free FA
Marine invertebrates’ primary source of fatty acids is macromolecular
organic food, as well as marine water itself. The latter contains a certain
amount of free dissolved fatty acids, however in very low concentrations.
The manner in which crustaceans uptake FA from marine water has been
studied primarily on annelids, brittlestars and sea urchins with the following
The accumulation and metabolization of free FA directly from
by marine invertebrates has been scientifically proven
FA uptake takes place directly across the invertebrates’ body wall,
not through a water filtration within alimentary tract
The rate of FA
accumulation was in most tests directly dependent
on the FA concentration
in the medium
In natural oceanic ecosystems direct FA uptake can probably
not more than a few percent of the organisms’ metabolism
Graph no. I
This graph shows the uptake of linoleic acid by sea worm Nainereis
dendritica as a function of incubation time in medium. The quantity of
accumulated FA grows linearly in time, thus longer the animal is exposed
to the dissolved fatty acid, the more will by uptaken.
Graph no. II
This graph shows the uptake velocity of palmitic acid (in 10-9mol
g-1 hod-1) by sea worm Stauronereis rudolphi as a function of molar concentration
of FA in substrate. It can be stated the uptake velocity grows with FA
concentration, although in the certain concentration interval is almost
ACCUMULATION OF FREE FATTY ACIDS FROM SEA WATER BY MARINE INVERTEBRATES, JOHN K. TESTERMAN', Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California 92664
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