12th Class Chemistry Chapter 14 Macromolecules Short Questions Answer

Molecules of high molar mass usually greater than 10,000 are called macromolecules. The substances like natural and synthetic polymers as carbohydrates proteins lipids enzymes steroids cholesterols are macromolecules.

The polymers are macromolecules and may be inorganic or organic in nature. The inorganic polymers are diamond graphite and sand etc. Organic polymers contain bio-polymers like lipids proteins carbohydrates and nucleic acids. Synthetic organic polymers are plastic rubber and synthetic fibre.

The polymers are produced due to the repetition of monomers. This repetition can be linear branched or network.

The number of repeating units in the chain which determines the length of the polymer chain is called degree of polymerization. It is abbreviated as D.P.

The sum of atomic masses of all the atoms present in the molecule of a polymer is molar mass of that polymer. Molar mass of a polymer = molar mass monomer × degree of polymerization.

In a homopolymer the polymerization takes place among the monomers of single type. In copolymer more than one types of monomers are there and in terpolymers three different types of monomers are there.

Thermoplastic polymers soften on heating and become rigid again on cooling like PVC nylon etc. Thermosetting polymers become hard on heating and softness can not be gained. Polyurethenes or epoxy resins are the best examples.

Polymerization can be addition and condensation. Addition polymerization can involve the free radicals or the ions in them.

Dibenzoyl peroxides acting as catalysts generate the free radical and polythene is formed by free radical mechanism.

Various types of monomers are used to prepare acrylic resins. For example Methyl methacrylate acrylic acid butyl acryleate give the acrylic resins. Acrylic resins are used for the manufacture paints for car industry and water based weather resistant paints.

Bio-polymers are life molecules and they are built up from the skeleton of carbon atoms. They are carbohydrates lipids proteins and nucleic acids.

Bio-polymers are life molecules and they are built up from the skeleton of carbon atoms. They are carbohydrates lipids proteins and nucleic acids.

Carbohydrates are the compounds of carbon hydrogen and oxygen with the general formula.C_x(H₂O)_y X and y can be equal or different.
They may be called hydrate of carbon.

Carbohydrates may be monosacchrides like glucose oligoscchride like sucrose and polysaccharides like starch. It depends upon that how many monosacchrides are there.

Those monosacchrides which have aldehydic group in them are called aldoses like glucose. Those monosacchrides which have ketonic group in them are called aldoketoses like fructose. There are many other examples as well.

When two molecules of monosacchride units join with each other they give a disaccharide. The best examples are sucrose glactose and mannose. Oligosaccharide are prepared from 2 to 9 monosaccharides units. H₂O molecules is eliminated during combination.

Lactose is called milk sugar and it is found in the milk of all animals. It is present in cow’s milk between 4-6% and human milk contains 5-8%.

Polysacchrides are naturally occurring polymers. Some important polysaccharides are starch cellulose glycogen insulin and dextrine.

Starch is found in wheat rice maize potatoes and barley. Actually it a mixture of two polysaccharides i.e. amylase and amylopectin.

Glycogen is the animal starch. It is the reserve carbohydrate of animals. It is found in liver muscles yeast and mushrooms.

Proteins are the high molecular weight materials which upon complete hydrolysis give amino acids. Proteins have carbon hydrogen oxygen nitrogen and sulphur. Proteins are the basis of photoplasma and are resent in all living organism.

Keeping in view the physical and chemical properties proteins have three types i.e. simple protein compound or conjugated proteins and derived proteins.

Those proteins which give only one amino acid upon gydrolysis are called simple proteins. Albumens globulins lactoglubulins and legumin are the best examples.

Conjugated proteins are those which upon hydrolysis give an amino acid and non-protein group. This non-protein group is called prosthetic group. Phosphoproteins are conjugated with phosphoric acid.

Those proteins which are derived from simple and conjugative proteins are called derived proteins. For example peptone and poly-peptides are the derived proteins.

Keeping in view the functions of proteins there are structural proteins hormones and enzymes.

We come to know about the shape in which the large amino acid chain exists. Sometimes the amino acid chains are coiled into a spiral which is called helix. This helix can be right handed or left handed.

According to their tertiary structures the helix of a protein is thought to be a piece of rope. This piece of rope is free to bend twist and fold.

It is the disruption of structure of proteins by heat by change of PH or by using strong oxidizing and reducing agents. Albumin is a protein and when egg albumin is heated it hardens and this change is irreversible.

Proteins help in the formation of protoplasm. They can act as catalyst or carriers of oxygen and act as harmones. In industry they are used for tanning of hides.

Lipids are naturally occurring organic compounds of animal and plants which are soluble in organic solvents and belong to very heterogenous group of substances. Simple lipids are of two types (i) Fats and oils. (ii) Waxes. They have great nutritional values. They provide energy to animal body for maintaining optimum body temperature. Their molecule is made up of our molecule of glycerol and three of a fatty acid.

Lipids are insoluble in water but soluble in ether chloroform and benzene. They are the primary building blocks of fatty acids glycerol and sterols. They can be used by living organisms.

Fats and oils have three major food factors required for the human body i.e. proteins carbohydrates fats and oils.

Animals plants and marine organisms are the sources of fats and oils. Butter and ghee are the fats which are obtained from milk.

GLycerides are the esters of a fatty acid with glycerol. In simple glycerides all the allyl group attached with the carbonyl group are identical.

Those glycerides which have carbon-carbon double bond present in them are normally liquid at room temperature. Glyceryl trioleate is liquid and has melting point of -5Cᵒ. If the alkyl portion of the glyceride is saturated it is called fat and it is solid at room temperature. Glyceryl tristearate is one of the example.

Fats and oils are hydrolyzed by enzymes which acts as catalysts. These enzymes are called lipases. This hydrolysis takes place in the digestive tract of the human beings and anmals.

It is the hydrolysis of triglycerides by alkalies to prodce glycerol and soap. Soap is sodium or potassium salt of long chain carboxylic acids.

Lipids are classified into three types. i) Simple lipids ii) Compound lipids iii) Derived or associated lipids.

The conversion of unsaturated glycerides by passing hydrogen through that in the presence of nickel into a saturated fat is called hardening of oil. The double bond to be saturated is in alkyl peotion of the oil.

The spoilage of fats and oils to give an odour is called rancidity. It is due to hydrolytic reaction or oxidative reaction. In both reactions a foul smell of aldehyde and fatty acid is given.