The areas labelled A, B, C, D are in order Examine the image of a phospholipid, below. Note that some areas are labelled hydrophobic, and others are hydrophilic. What is the term we use for molecules, like this one, that have both properties? In an aqueous environment, phospholipids will form which of the following? Which of the following common materials behaves as an amphoteric molecule? The first cells likely developed from spontaneous associations of phospholipids, called?
Biochemistry of Lipids: Fatty Acids, Omega Fats, Triglycerides, Phospholipids, Eicosanoids
The breakdown of lipids involves the breaking of a bond using water. This is a process called? Back to top. Remove Ad. Removing ad is a premium feature.
More Sbi4u Biochemistry Unit Quizzes. Although biological lipids are not large macromolecular polymers e. Many of these molecular building blocks are similar, or homologous, in structure. The homologies allow lipids to be classified into a few major groups: fatty acids, fatty acid derivatives, cholesterol and its derivatives, and lipoproteins. This article covers the major groups and explains how these molecules function as energy-storage molecules, chemical messengers, and structural components of cells.
Fatty acids rarely occur as free molecules in nature but are usually found as components of many complex lipid molecules such as fats energy-storage compounds and phospholipids the primary lipid components of cellular membranes. This section describes the structure and physical and chemical properties of fatty acids. It also explains how living organisms obtain fatty acids, both from their diets and through metabolic breakdown of stored fats.
Biological fatty acids, members of the class of compounds known as carboxylic acids , are composed of a hydrocarbon chain with one terminal carboxyl group COOH. The fragment of a carboxylic acid not including the hydroxyl OH group is called an acyl group.
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Most biological fatty acids contain an even number of carbon atoms because the biosynthetic pathway common to all organisms involves chemically linking two-carbon units together although relatively small amounts of odd-number fatty acids do occur in some organisms. The apparent repressive effects of corn oil may be due to its w 6 content since w 3 and w 3 present in menhaden oil had no apparent detrimental effects. The growth suppressing effects of w 6 were also noted when 3 percent corn oil was added to 3 percent beef tallow and 3 percent menhaden oil.
The growth suppression caused by unsaturated fatty acids does not appear to be limited to w 6 fatty acids. Linseed oil high in w 3 in the diet of catfish resulted in growth suppression similar to that caused by corn oil compared with dietary beef tallow, olive oil and menhaden oil. This fish has an EFA requirement for both w 3 and w 6 fatty acids. The best weight gains and feed conversions are obtained in fish receiving a diet containing both 1 percent w 6 and 1 percent w 3.
With the carp, w 3 and w 3 at 0. Carp fed a fat-free, or EFA deficient, diet incorporated high levels of w 9 in their lipids, especially in the phospholipids. Corn oil high in w 6 and cod liver oil high in w 3 in a mixture are most favourable for the growth of eels. The eel requires w 6 and w 3 in the same proportion as the carp, but at a lower level in the diet; namely, 0. The addition of and to the diet result in the synthesis of saturated and monoenoic fatty acids of chain lengths up to C18; however, increased levels of w 9 noted in trout and mammals have not been reported in plaice.
Plaice fed dietary w 6 and w 3 will not produce significant amounts of w 6, w 3, or w 3.
The turbot also appears to be unable to convert dietary w 6 to w 6 when fed corn oil, or to convert endogenous w 9 to w 9 when fed the EFA deficient diet. Although it appears to have an EFA requirement for w 3 fatty acids such as are present in cod liver oil, this requirement is not satisfied by w 3. The chain elongation and desaturation of l w 9, w 6, or w 3 has been found to be very limited percent in turbot compared to the rainbow trout where 70 percent of the w 3 was converted to w 3. The required level of long-chain w 3 fatty acids for turbot is at least 0. The EFA requirement of the red sea bream is not satisfied by either linoleic acid of corn oil or supplemented linolenate.
A mixture of w 3 and w 3 supplemented to the corn oil diet has been shown to be effective in improving growth and condition of these fish. Thus, even in warm water, marine fish seem to require not just w 3 fatty acids but 0 3 fatty acids of 20 to 22 carbon-chain length. A direct correlation between feed efficiency and the level in the lipids of the red sea bream has been postulated. The process is, however, inhibited in fundulus by high levels about 5 percent of these PUFAs of w 6 or w 3 in the diet.
It is interesting to note that the channel catfish, which also exhibits negative growth response to dietary w 6 or w 3, incorporates very high levels of into its body lipids. The inclusion of either w 6 or w 3 in the diet reduces the levels of fatty acids in body lipids. A similar reduction has also been observed in red sea bream liver phospholipid when either of the PUFAs is added to the diet.
The pathways of fatty acid metabolism have been reviewed by Mead and Kayama Fish are able to synthesize, de novo from acetate, the even-chain, saturated fatty acids, as shown in Figure 1.
Chemistry of lipids and Eicosanoids-Viva questions (Solved)
Radio tracer studies have shown that fish can convert to the w 7 monoene and to the w 9 monoene. The w 5, w 11 and w 3 monoenes are proposed based on the identification of these isomers in the monoenes of herring oil. Fish are unable to synthesize any fatty acids of the w 6 and u3 series unless a precursor with this w structure is present in the diet.
Fish are able to desaturate and elongate fatty acids of the w 9, w 6, or w 3 series as outlined in Figure 1. There is competitive inhibition of the elongation desaturation of fatty acids of one series by members of the other series. The w 3 fatty acids are the most potent inhibitors, the w 9 are the least. The ability to elongate and desaturate fatty acids is not the same in all species of fish, as was noted earlier. The turbot was able to desaturate and elongate only percent of w 9, w 6, or w 3, when given the C 14 labelled fatty acid; in the rainbow trout, 70 percent of the label from w 3 C 14 was found in w 3.
The essential fatty acids are not unique in their ability to supply energy.
NUTR.4060 Biochemistry of Lipids(Formerly 36.406)
The b -oxidation of fatty acids in fish is basically the same as in mammals. The EFA and saturated and monoenoic fatty acids are all equally utilized by fish for energy production. It is possible that EFA plays an important role in the permeability as well as the plasticity of membranes. The role of w 3 fatty acids in membrane permeability may be one of the factors accounting for differences in content of this family of fatty acids between freshwater and marine fish.
Fish mitochondria with high levels of the w 3 PUFA and very low levels of w 6 fatty acids are very similar to mammalian mitochondria with respect to cytochrome content, b -oxidation of fatty acids, operation of the tricarboxylic acid cycle, electron transport, and oxidative phosphorylation. The w 3 PUFA may play the same role in fish that the w 6 fatty acids play in rats. The EFA play another role in the mitochondria. In addition to their importance in membrane structure, the EFA are important in some enzyme systems. Unsaturated fatty acids play an important role in the transportation of other lipids.
It has been repeatedly shown that feeding PUFA will lower the cholesterol levels in animals with above-normal blood lipid and cholesterol levels. Fish oils are more effective in lowering cholesterol levels than are most dietary lipids. The major portion of the fatty acids absorbed across the intestinal mucosa are transported as protein-lipid complexes stabilized by phospholipids.
The low body temperature in fish probably results in a greater importance for unsaturation in transport of lipids than in homeothermic animals. These types of fatty acids are very labile on oxidation.
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The products of lipid oxidation may react with other nutrients such as proteins, vitamins, etc. The effect of oxidized lipids on dietary proteins, enzymes and amino acids have been demonstrated. The use of oxidized menhaden oil in the diets of swine and rats caused decreased appetite, reduced growth, yellowish-brown pigmentation of depot fat, and decreased haemoglobin and haematocrit levels.
The negative effects of the oxidized fish oils were reversed by the addition of alpha-tocopherol acetate or ethoxyoquin to the diet. Much of the use of vegetable oils in fish diets in the s and s might, in part, have been based on their greater stability in prepared diets. It has been demonstrated that rancid herring and hake meals in fish feeds caused dark colouration, anaemia, lethargy, brown-yellow pigmented liver, abnormal kidneys, and small gill clubbing in chinook salmon.
The symptons can be alleviated by addition of alpha-tocopherol to the diets containing rancid fish meals.