Phosphoacylglycerols

Choline Ethanolamine Serine

Phosphatylcholine

Phosphatylcholine, structure of molecule

Diagram of a section of a bilayer membrane.

Space-filling model of a section of phospholipid bilayer membrane.

Lipid bilayer of plasma membrane

Sphingolipid

Sphingosine

Sphingolipids in which the esterifying group is phosphoric acid to which choline is attached are called sphingornyelins. sphingornyelins. Sphingomyelins are found in all cell membranes and are important structural components of the myelin sheath, the protective and insulating coating that

surrounds nerves SphingomyelinsSphingomyelins

Glycolipid

Cerebrosides Gangliosides

•Cerebrosides,Cerebrosides, the simplest of such carbohydrate-containing lipids, usually have а glucose or galactose as the carbohydrate unit. •Gangliosides Gangliosides contain more complex carbohydrate heads; up to seven monosaccharide units are present.

Nonsaponifiable Lipids Lipids do not undergo hydrolysis in alkaline solution.

Nonsaponifiable Lipids: steroids, eicosanoids, terpenes, pheromones, fat-soluble vitamins

A steroid is a lipid whose structure is based on the tetracyclic (four-ring) system shown in the following examples. Three of the rings are six-membered, while the fourth is five-membered. Steroids have many diverse roles throughout both the plant and animal kingdoms.

Pentahydrofenantrene (sterane)

Cholesterol is the most abundant steroid in the human body

Cholesterol, an unsaturated alcohol whose structure is the most abundant animal steroid. It has been estimated that a 60 kg person has a total of about 175 g of cholesterol distributed throughout the body. Much of this cholesterol is bonded through ester links to fatty acids, but some is found as the free alcohol. Gallstones, for example, are nearly purecholesterol.

Cholesterol serves two important functions in the body. First, it is a minor component of cell membranes, where it helps to keep the membranes fluid. Second, it serves as the body’s starting material for the synthesis of all other steroids, including the sex hormones.

Bile acidsBile acids

The liver secretes а clear, golden-yellow, viscous fluid The liver secretes а clear, golden-yellow, viscous fluid known as bile. It is stored in the gall bladder (cistifellea) known as bile. It is stored in the gall bladder (cistifellea) and is mainly useful for digestive system. and is mainly useful for digestive system.

Steroids hormones.Steroids hormones.

Hormones are chemical messengers produced by ductless glands (endocrine).

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Fat-Soluble VitaminsFat-Soluble Vitamins

Vitamins are divided into two broad classes on the basis of their solubility: • Those that are fat soluble, and hence classified as

lipids.• Those that are water soluble.

The fat-soluble vitamins include A, D, E, and K.

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Vitamin AVitamin A

• Occurs only in the animal world.• Found in the plant world in the form of a provitamin in

a group of pigments called carotenes.

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Vitamin AVitamin A

The best understood role of Vitamin A is its participation in the visual cycle in rod cells.• the active molecule is retinal (vitamin A aldehyde),

which forms an imine with an -NH2 group of the protein opsin to form the visual pigment called rhodopsin.

• the primary chemical event of vision in rod cells is absorption of light by rhodopsin followed by isomerization of the 11-cis double bond to the 11-trans configuration.

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Vitamin A and the Chemistry of VisionVitamin A and the Chemistry of Vision

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Vitamin DVitamin D

A group of structurally related compounds that play a role in the regulation of calcium and phosphorus metabolism.• The most abundant form in the circulatory system is

vitamin D3.

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Vitamin EVitamin E

Vitamin E is a group of compounds of similar structure, the most active of which is -tocopherol.

• In the body, vitamin E functions as an antioxidant; it traps peroxy radicals of the type HOO• and ROO• formed as a result of oxidation by O2 of unsaturated hydrocarbon chains in membrane phospholipids.

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Vitamin KVitamin K

The name of this vitamin comes from the German word Koagulation, signifying its important role in the blood-clotting process.