Lipids, Fats, and Biochemistry

Arachidonic acid contains 20 carbon. it is a polyunsaturated omega-6 fatty acid found in phospholipid of the membrane of cells liver, brain, and muscles.

Unsaturated fat is a fat or fatty acid in which there is one or more double bond in the fatty acid chain. A fat molecule is monounsaturated if it contains one double bond, and polyunsaturated if it contains two or more double bonds.

Answer is option A i.e. "Polysaturated"
Fats are one of the main macro-nutrients. Fats serve both structural and metabolic functions. There are four types of fats: saturated, monounsaturated, trans and polyunsaturated.
1) Saturated fats have no double bonds between the carbons in the chain.
2) Monounsaturated fats have one double bonded carbon in the chain
3) Polyunsaturated fats have multiple double bonds.
4) Trans fats are types of unsaturated fats formed by hydrogenation of oils.

Linolenic acid 18 carbon containing unsaturated fatty acid with three double bonds. It is found in plants and required in the formation of prostaglandin.

Flaxseed oil contains alpha-linolenic acid (ALA), a form of omega-3 fatty acid that is only converted in small amounts to active forms of omega-3, like EPA and DHA. It is high in Omega-3 Fatty Acids.

Fatty acids with no carbon-carbon double bonds are said to be saturated those with at least one double bonds are unsaturated. Unsaturated fatty acids with more than one carbon-carbon double bond are referred to as polyunsaturated. Two essential polyunsaturated fatty acids are linoleic acid made up of 18 carbon atoms and having 2 double bonds and linolenic acid made up of 18 carbon atoms and having three double bonds. They cannot be synthesized by mammals and must be supplied in their diet. Arachidonic acid is made up of 20 carbon atoms and has four double bonds.

The wall of the mature pollen grain is stratified. It comprises two principal layers the internal layer is called as intine and the outer layer is called as exine. The intine is pecto-cellulosic in nature. The exine is chiefly composed of a class of material called as sporopollenin. Chemical analysis has revealed that it is a mixture of biopolymers, containing long chain fatty acids, phenylpropanoids, phenolic compounds and carotenoids. It is derived from carotenoids by oxidative polymerization. Sporopollenin is resistant to physical and biological decomposition. Because of this property, the pollen grain walls are often preserved for long periods in fossil deposits.

Long chain molecules of fatty acids are formed by polymerisation of 2 carbon compounds. A fatty acid is a carboxylic acid with a long aliphatic tail (chain), which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids that have carbon-carbon double or triple bonds are known as unsaturated. Fatty acids without double bonds are known as saturated. They differ in length as well. Long-chain fatty acids (LCFA) are fatty acids with aliphatic tails 13 to 21 carbons.

Cutin is a polymer which is the main component of the plant cuticle, which covers all aerial surfaces of plants. Cutin consists of $\omega$-hydroxy acids and their derivatives, which are interlinked via ester bonds, forming a polyester polymer of indeterminate size. There are two major monomer families of cutin, the C16 and C18 families. The C16 family consists mainly of 16-hydroxy palmitic acid and 9,16- or 10,16-di hydroxy palmitic acid. The C18 family consists mainly of 18-hydroxy oleic acid, 9,10-epoxy-18-hydroxy stearic acid, and 9,10,18-trihydroxystearate.

Triglycerides or neutral fats or true fats are the esters of three molecules of fatty acids and one molecule of trihydric alcohol glycerol. Hence, they are also called triglycerides. Oils are liquid at room temperature. They possess either small or unsaturated fatty acid.

Linoleic acid (LA) is an essential fatty acid but is not synthesized in the human body. LA is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins, leukotrienes (LTA, LTB, LTC), and thromboxane (TXA). It is found in the lipids of cell membranes. It is abundant in many vegetable oils, comprising over half of poppy seed, safflower, sunflower, corn, and soybean oils.

Wax is ester of fatty acids with long chain monhydric alcohol. Cholesterol is the type of alcohol found in wax. It is not easily hydrolyzed like fat. It gives protection. It prevents excessive drying. It also provides water resistance. Beeswax, carnuba wax are examples of wax.

Saturated fatty acids are the fats that do not contain a double bond between the carbon atoms. Fatty acids chain are straight. Saturated fats are mostly found in animal fats and animal product. It is solid at room temperature e.g., butter. Saturated fatty acids are high melting than unsaturated fatty acids(low melting point and liquid at room temperature). Thus, the correct option is D.