Question

1. Discuss the three types of lipid reactions. Mention all nutritional and health issues related to those reactions 00: م

Answer 1

Lipids are compounds that are insoluble in water but are completely soluble in organic solvents like ether and chloroform. Lipids include fats and oils (triglycerides and triacyglycerols), fatty acids, phospholipids, and cholesterol.
Fats and oils are esters of glycerol and fatty acids. They are very muchimuch in our diet for energy sources of essential fatty acids and fat-soluble vitamins.They also contribute satiety, flavor, and palatability to the diet.

Properties of Lipids:
(1.) lipids may be either liquids or non-crystalline solids at room temperature.
(2.) pure fats and oils are colorless, odorless, and tasteless.
(3.) They are energy-rich organic molecules
Insoluble in water
(4.) Soluble in organic solvents like alcohol, chloroform, acetone, benzene, etc.
(5.) No ionic charges
(6.) Solid triglycerols (Fats) have high proportions of saturated fatty acids.
(7.) Liquid triglycerols (Oils) have high proportions of unsaturated fatty acids.

1. Hydrolysis of triglycerols
Triglycerols like any other esters react with water to form their carboxylic acid and alcohol– a process known as hydrolysis.
2. Saponification:
Triacylglycerols may be hydrolyzed by several procedures, the most common of which utilizes alkali or enzymes called lipa­ses. Alkaline hydrolysis is termed saponifica­tion because one of the products of the hydrolysis is a soap, generally sodium or potassium salts of fatty acids.
3. Hydrogenation
The carbon-carbon double bonds in unsaturated fatty acids can be hydrogenated by reacting with hydrogen to produce saturated fatty acids.
4. Halogenation
Unsaturated fatty acids, whether they are free or combined as esters in fats and oils, react with halogens by addition at the double bond(s). The reaction results in the decolorization of the halogen solu­tion.
5. Rancidity:
The term rancid is applied to any fat or oil that develops a disagreeable odor. Hydrolysis and oxidation reactions are responsible for causing rancidity. Oxidative rancidity occurs in triacylglycerols containing unsaturated fatty acids.

Fatty acids generally consist of a straight alkyl chain, terminating with a carboxyl group. The number of carbons in the chain varies, and the compound may be saturated (containing no double bonds) or unsaturated (containing one or more double bonds). Short- and medium-chain saturated fatty acids (SFAs) (4 to 12 carbons in length) are found in milk fat, palm oil, and coconut oil. Other animal and vegetable fats contain predominantly longer-chain SFAs (more than 14 carbons in length) and are found chiefly in meats, butterfat, and some vegetable oils. Monounsaturated fatty acids (MUFAs), such as oleic acid, contain one double bond per molecule, whereas polyunsaturated fatty acids (PUFAs), such as linoleic acid, contain more than one. Linoleic acid is classified as an essential nutrient, since the body requires it but cannot synthesize it. Arachidonic acid is also required by the body but can be synthesized from linoleic acid, which is abundant in oils from corn, soybeans, and safflower seeds.
Linoleic acid (18 carbons with 2 double bonds) and arachidonic acid (20 carbons with 4 double bonds) belong to the omega(ω)-6 group of fatty acids, since the first double bond, counting from the methyl end of the molecule, occurs at carbon number 6. Since linoleic acid has 18 carbon atoms and 2 double bonds, it is usually represented in shorthand as C18:2, ω-6. Under this classification system, oleic acid (C18:1, ω-9) belongs to the ω-9 group, and the PUFAs in fish oils currently receiving much attention belong to the ω-3 group. Chief among these ω-3 fatty acids are eicosapentaenoic acid (EPA), which has 20 carbons and 5 double bonds (C20:5, ω-3), and docosahexaenoic acid (DHA), which has 22 carbons and 6 double bonds (C22:6, ω-3).
A growing body of evidence from studies in animals, including nonhuman primates, indicates that α-linolenic acid, or its longer-chain derivates EPA and DHA, are essential in the diet. These fatty acids appear to play distinctive roles in the structure and function of biologic membranes in the retina and central nervous system.
Unsaturated fatty acids form geometric isomers, i.e., the carbon chains are on the same side of the double bond in a cis isomer and on opposite sides of the bond in a trans isomer. Naturally occurring geometric isomers in food are mainly cis isomers, but hydrogenation of oils in the manufacture of margarine and shortening results in formation of some trans isomers. This latter process occurs naturally in the rumen of ruminants.
Phospholipids contain glycerol, fatty acids, phosphate, and, with such exceptions as phosphatidylglycerol and phosphatidylinositol, a nitrogenous component. Lecithin, for example, is made up of glycerol, two fatty acids (one saturated, usually), phosphate, and choline. Phospholipids are important structural components of brain and nervous tissue, of membranes throughout body tissues, and of lipoproteins—the carriers of cholesterol and fats in the blood.
Cholesterol and plant sterols, such as sitosterol, are high-molecular-weight alcohols with a characteristic cyclic nucleus and are unrelated to the structure of fats or phospholipids. Cholesterol frequently exists in foods and body tissues esterified to one fatty acid per molecule. It is a component of membranes in body cells and is required for normal development of the brain and nervous tissue. Furthermore, it is the precursor to bile acids, steroid hormones, and 7-dehydrocholesterol in the skin, which in turn is the precursor to vitamin D.
Cholesterol occurs naturally only in foods of animal origin. The highest concentrations are found in liver and egg yolk, but red meats, poultry (especially the skin), whole milk, and cheese make significant contributions to the diet.

The answer for the correct order of acidity is (b)C>D>A>B