Lipids and their function - class-XI

Palmitic acid or hexadecanoic acid was discovered by Edmond Fremy. It is commonly found in plants, animals and microorganisms.Its chemical formula is CH$ _3$(CH$ _2$)$ _{14}$COOH.It is a saturated fatty acid.

Essential fatty acids are those that the body cannot synthesize. Linoleic and linolenic acids are essential. Oleic acid is non-essential. Stearic acid is a saturated fatty acid, not an unsaturated one.

Steroids are crystallisable lipids having four hydrocarbon rings consisting of three cyclohexane and one cyclopentane ring and a long hydrocarbon side chain. Fatty acids are absent. In animals, sterols are precursors of steroid hormones and vitamin D. Cholesterol is a sterol of animal systems which forms bile salts, is a component of plasma membrane and hormones.

Essential fatty acids are those fatty acid which plays an important role in the biological process and they can be metabolized easily. These acts as a fuel rather getting deposited as fat in the body. The human body cannot synthesize essential fatty acids. Alpha-linolenic acid and linoleic acid are the two essential fatty acid. It was discovered by Evans and Burr.

Lanolin is also known as wool fat, wool grease or wool wax. It is secreted by the sebaceous glands of wool-bearing animals. It is obtained by the sheep which has been raised specifically for wool. It helps the sheep to shedd water from their coats and protect them from changing environmental conditions. Wax is a long chain of sterol ester. It is also used in commercial production of lubricants, rust-preventive coatings, shoe polish.

Unsaturated fats are liquid at room temperature as they have double bonds. The essential fatty acids like alpha-linolenic acid and linoleic acid are unsaturated as they have double bonds. Sunflower oil is a non- volatile oil. It is a mixture of mostly oleic acid (omega-9)-linoleic acid (omega-6). The composition precisely comprises of  59% linoleic acid, oleic acid 30%, stearic acid 6%, and palmitic acid is 5%.

Biological pigments are often terpenes (a), chemical messengers are prostaglandins (b), blood constituents include sodium chloride (c), and steroids have four carbon rings (d). Matching: a-4, b-3, c-1, d-2.

Saturated fatty acids have single bond and are solid at room temperature. Hydrogenation is the process which involves the addition of hydrogen in the presence of nickel, palladium or platinum. On addition of hydrogen, the double bonds of unsaturated fatty acids are reduced to saturated fatty acid. Stearic acid is a saturated fatty acid as it has single carbon bonds. It has eighteen carbon with chemical formula of  C$ _{18}$H$ _{36}$O$ _2$. It can be produced by saponification of the triglycerides.

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.

Fatty acids are of two types based on the single and double bonds in their hydrocarbon chain. The saturated fatty acids have only single bonds in their hydrocarbon chain. These are mostly obtained from an animal source. They exist as solids at room temperature. The unsaturated fatty acids have both the single and double bonds in their hydrocarbon chain. These are mostly derived from plant sources. They exist as a liquid at room temperature.

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.

Unsaturated fats are liquid at room temperature as they have double bonds. Saturated fatty acids have the single bond and are solid at room temperature. Hydrogenation is the process which involves the addition of hydrogen in the presence of nickel, palladium or platinum. On addition of hydrogen, the double bonds of fatty acids are reduced. 

Lipase is a type of enzyme known as hydrolse and is resposible for catalysing the hydrolysis of triglycerides into fatty aids and glycerol.

Arachidonic acid is a carboxylic acid which has 20 carbon and four double bonds in the cis configuration. It is a polyunsaturated fatty acid (PUFA). It is mainly present in the membrane phospholipids and in platelets. It is also found in liver, erythrocytes, skeletal muscle, cardiac muscle. Meat, egg, and fish are rich sources of arachidonic acid.

Essential fatty acids are those fatty acids that body cannot produce on its own and therefore must be supplied from the diet. Two primary essential fatty acids are linoleic acid and alpha-linoleic acid. Linoleic acid (omega-6) occurs in plant oils like corn oil, palm oil, soybean oil, sunflower oil. Alpha-linoleic acid (omega-3) occurs in fowl and fish like salmon, sardines, tuna.

Unsaturated fatty acid is those which contain one or more double bond in their fatty acids. Generally, it is found in plants fats. It also lowers blood cholesterol. Linoleic is unsaturated fatty acid containing two double bonds. Sunflower oil contains highest linoleic acid. Thus, the correct answer is A.

Fat is stored reserve for the body which provides energy. These are triesters of glycerol. It is obtained from fatty acids and glycerol. It consists of one glycerol molecule and three fatty acid molecules. The carboxyl end of the fatty acid combines with the three -OH groups of the glycerol to form the ester. So, the correct answer is option B.

Fatty acids are of two types, the saturated fatty acids that have single bond across the carbon chain and the unsaturated fatty acids that have one or more double bond across the carbon chain. When there are more than one double bonds, they are called the polyunsaturated fatty acids. These are called the essential fatty acids as they cannot be synthesized in the body and must be supplied through the external source. Linoleic acid and linolenic acid are the essential fatty acids.

Lipids (triglycerides) are esters of fatty acids and glycerol (a trihydric alcohol). Hydrolysis breaks them down into these components.

An 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 more than one double bond. Where double bonds are formed, hydrogen atoms are eliminated.

Arachidonic acid is not one of the essential fatty acids. Rather it is conditionally essential fatty acid which, becomes essential if its precursor, linoleic acid is deficient thereby resulting in the inability to convert linoleic acid to arachidonic acid. However, some mammals lack the ability or have a very limited capacity to convert linoleic acid to arachidonic acid, making it an essential part of their diets. So, the correct answer is 'Arachidonic acid'.

Essential fatty acids are those compounds which cannot be synthesized by human and must be ingested externally. Examples of essential fatty acid include linoleic (omega-6 fatty acid) and alpha-linolenic acid (omega-3 fatty acid). Linoleic acid is converted to arachidonic acid. Arachidonic acid is an omega-6 unsaturated fatty acid required by proper functioning of body. 

Fatty acids are long, straight chain carboxylic acids. A fat (or oil) is formed when three fatty acid molecules react with a glycerol molecule to yield a triglyceride. Fats in the body are transported and stored as triglycerides.

Cutin is indeed a hydroxy fatty acid polymer that forms the plant cuticle. Starch is a polysaccharide composed exclusively of alpha-glucose monomers linked together. Both statements are correct.

Linolenic acid is a polyunsaturated fatty acid containing multiple double bonds. Oleic acid is a monounsaturated fatty acid with one double bond. Palmitic acid and stearic acid are saturated fatty acids with no double bonds. Thus, 1 and 2 are unsaturated fatty acids.

When one or more double bonds are present between the carbon chains of the fatty acids it is known as unsaturated fats. They have a large number of fatty acid molecules per fat molecule. Due to the presence of double bonds they contain a lesser number of hydrogen bonds as compared to the saturated fatty acid molecules.

Fatty acids are two main types- saturated and unsaturated fatty acids are without double bonds in their carbon chains. They have higher melting points and are solids at room temperature. They have a general formula of $C _nH _{2n}O _2$,e.g., $C _{16}H _{32}O _2$ (palmitic acid), $C _{18}H _{36}O _2$ (stearic acid).

Fatty acids are carboxylic acids with hydrocarbon chains of 4 to 36 carbons. In some fatty acids, this chain is fully saturated (meaning it cannot accept any more hydrogens) and unbranched; other fatty acids contain one or more double bonds (thus, they can be hydrogenated when the double bonds will get converted into single bonds).

Arachidonic acid is not an essential fatty acid because it can be synthesized by the cells in the body from linoleic acid. All the other three are essential fatty acids.