Learn about Derived Lipids
Derived Lipids:
These are components obtained by degradation of simple and compound lipids or precursors of them. They contain fatty acids and alcohols, sterols, hydrocarbons and Vit A, D, E, and K (fat soluble vitamins).
Fatty acids:
- Fatty acids are formed by hydrolyzing fats.
- In natural fats, fatty acids generally contain carbon atoms in even number because they are obtained from 2-carbon units.
- Fatty acids may contain double bonds (unsaturated) or may not possess any double bonds (saturated).
- Numbering of carbon atoms start from carboxylic carbon atom. Carbon 2 can be called as α- carbon.
Types of Fatty Acids:
Based on structure fatty acids can be classified into:
i. Straight chain.
ii. Branched chain.
iii. Substituted.
iv. Cyclic.
Straight Chain Fatty Acids:
These are again classified into two types based on occurrence of double bond.
1. Saturated
2. Unsaturated
Saturated Fatty Acids:
These fatty acids occur in both plants and animals. These are straight chain compounds and the formula is CnH2n+1COOH. The double bonds do not occur in their structure.
Unsaturated Fatty acids:
These fatty acids possess one or more double bonds in their structure. If fatty acid is highly unsaturated, it tends to be rancid.
To know detailed structures and types of unsaturated fatty acids go to the given link:
From the 20 carbon unsaturated fatty acid, eicosanoids are formed.
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| Eicosanoid formation |
Under eicosanoids, there are many sub families such as prostanoids, leukotrienes, lipoxines etc.
Protanoids consists of prostaglandins, thromboxanes and prostacyclins. These all are having 20 carbons in their structure. Double bond with trans conformation occurs at 13th carbon and hydroxyl group can be found at 15th position.
Prostaglandins:
These can be found in all mammals. They have crucial roles in pharmacological and physiological activities. These can act as local hormones. They are formed by cyclization of the polyunsaturated fatty acid. There are different types of prostaglandins based on substituent groups attached to the rings.
Prostacyclins:
Prostacyclins can be found in heart, vascular endothelium and kidneys. Prostacyclin synthetase enzyme catalyze the zsinthesis of prostacyclins. Renin production is stimulated by prostacyclins. Platelet aggregation can be inhibited by prostacyclins. They reduce blood pressure. Hyperlipemia, Vitamin E deficiency and radiation inhibit prostacyclins.
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| Prostacyclins |
Thromboxane:
They help in smooth muscle contraction. They can be found in platelets and contain oxane ring. They increase blood pressure. They influence the secretion of serotonin and Ca2+ in the platelet granules. They can be inhibited by imidazole.
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| Thromboxane |
Leukotrienes:
These eicosanoids derived through the lipoxygenase pathway. First these are observed in leukocytes. Three conjugated double bonds are present in their structure. They play important role in mucus secretion and vasoconstriction.
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| Leucotrienes |
Branched Chain Fatty Acids:
Branched chain fatty acids are carbon chain saturated fatty acids with methyl branches. These are found mostly in bacteria. In human infants, these fatty acids play an important role in developing intestinal microflora.
Cyclic Fatty Acids:
These are less common fatty acids found in plants and bacteria. Chaulmoogric acid is best example for cyclic fatty acid which was used in treatment of leprosy.
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| Chaulmoogric acid |
Polyunsaturated fatty acids are cannot be synthesized in the body so these are essential fatty acids.
Steroids:
They possess cyclic nucleus which is similar to phenanthrene ring with a cyclopentane ring attached to it. Methyl side chains present at 10 and 13 positions. Sterol is the compound with hydroxyl groups and without carboxyl or carbonyl groups.
Steroids can be divided as follows:
Sterols—cholesterol, ergosterol, coprosterol.
Bile acids—Glycocholic acid and taurocholic acid.
Sex hormones—Testosterone, Estradiol.
Vitamin D—Vit. D2 and D3.
Adrenocortical hormones—Corticosterone.
Cardiac glycosides—Stropanthin.
Saponins—Digitonin.
Cholesterol:
It is present in all animals, but not in plant cells. It is also a monohydroxyalcohol and contains a double bond between C5 and C6. In this structure, all of the ring fusions (between A and B, B and C, and C and D) are trans, the hydrogen atoms or methyl groups attached to the bridgehead carbons project to opposite sides of the rings, and the rings are in the more stable chair conformation. The angular methyl groups at C18 and C19 , the 3-hydroxyl group, and the side chain at Cl7 all project toward the same side of the ring system. These substituents are indicated by solid lines and designated as β. A substituent group situated below the plane of the ring is in the α-orientation and is indicated with a dotted line. In general, the angular methyl groups are β-oriented, but the 3-hydroxyl group may be present in either the α- and β-orientation. In cholesterol, the 3-OH is in the β-orientation. Cholesterol has several functions including involvement in membrane structure, by modulation of membrane fluidity and permeability, serving as a precursor for steroid hormone and bile acid synthesis, in the covalent modification of proteins, and formation of the central nervous system in embryonic development.
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| Cholesterol |
Ergosterol:
It acts as precursor molecule of vitamin D. It can be found in ergot and yeast. When irradiated with UV radiation, B ring opens which gives anti-rachitic property to the ergosterol.
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| Ergosterol |
Coprosterol:
It can be found in feces. It is formed by reduction of the double bond between C5 and C6 of cholesterol by bacteria.
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