NCERT Solutions Class 11 Biology Chapter 9 - Biomolecules

Q1: What are macromolecules? Give examples.
Ans: Macromolecules are the biomolecules that are formed by the polymerisation of a huge number of micromolecules possessing higher molecular weight. Micromolecules are found in the colloidal state in the intercellular fluid due to their insoluble nature. Protein is a macromolecule.

Q3: What is meant by tertiary structure of proteins?
Ans: It is a structure that forms when the secondary coiled polypeptides are folded to produce a hollow, wollen ball-like structure. It is folded such that the functional side groups appear on the surface while the inactive side groups are found inside. This gives us a 3-dimensional view of a protein. Tertiary structure is absolutely necessary for the many biological activities of proteins.

Q3: Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.
Ans:
(a) 

Q4: Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., Cosmetics etc.)
Ans: Following is the list of proteins used as therapeutic agents. Insulin and Antibody ( mentioned in ncert), Oxytocin,  Antidiuretic Hormone( ADH), Thrombin, Fibrinogen, Renin and streptokinases.
Some other applications are

• They are used as artificial sweeteners. Thaumatin is a low-calorie sweetener.
• Proteins are used as dietary supplements to maintain health.
• They are used in creams and shampoos. (Caesin)

Q5: Explain the composition of triglyceride.
Ans: When glycerol combines with three fatty acids on each of the OH groups through ester bonds, it is known as a triglyceride.
All three fatty acids of triglyceride in pure fat are similar, while in mixed fat, they are dissimilar.

Q6: Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models).
Ans: Biomolecules can be represented by the ball and stick model. Here, the bonds which hold the molecule are indicated by sticks, while the atoms are represented by balls. The figure below is a model of D-glucose, where atoms of hydrogen are indicated by green balls, oxygen atoms are represented by pink balls, and carbon atoms are represented by grey balls.

Q7: Draw the structure of the amino acid, alanine.
Ans: The structure of Alanine is as follows:

Q8: What are gums made of? Is Fevicol different?
Ans: Gums are heteropolysaccharides formed by different monosaccharide units associated with glycosidic bonds. On the other hand, Fevicol is different from gums, as it is made up of synthetic polymers.

Q9: Find out a qualitative test for proteins, fats and oils, amino acids and test any fruit juice, saliva, sweat and urine for them.
Ans: Qualitative tests for proteins, amino acids and fats:

• Biuret test: The Biuret test for protein identifies the presence of protein by producing light blue to purple colour of the solution.
• Grease test for oil: Certain oils give a translucent stain on brown paper. This test can be used to show the presence of fat in vegetable oils.
• Ninhydrin test: If Ninhydrin reagent is added to the solution, then the colourless solution changes to pink, blue or purple colour depending on the type of amino acid.

Q10: Find out how much cellulose is made by all the plants in the biosphere and compare it with how much of paper is manufactured by man and hence what is the consumption of plant material by man annually. What a loss of vegetation!
Ans: The biosphere produces about 100 billion tonnes of cellulose out of 170 billion tonnes of total organic matter. Production of paper consumes about 0.5 billion tonnes of wood. Trees are also utilised for other purposes, including food, medicines, timber, spices, etc. An approximate estimate of 1.5 billion tonnes of food is required. Wood requirement for various purposes includes 2 billion tonnes. Therefore, it is difficult to gauge the annual consumption of plant material by man. Thus, the use of cellulose led to a great loss of vegetation.

Q11: Describe the important properties of enzymes.
Ans: The important properties of enzymes are as follows:

• The enzymes are generally proteins which are high molecular weight complex globular proteins. They can associate with non-protein substance for their activity.
• The enzymes do not start a chemical reaction but only accelerate it. They combine temporarily with the substrate molecules and are not consumed or changed permanently in the reaction which they catalyse.
• The enzyme controlled reactions are reversible.
• The enzymes are specific in action. An enzyme catalyses only a particular kind of reaction or acts on a particular substrate only.
• The enzymes are thermolabile i.e., heat sensitive and can function best at an optimum temperature. Similarly, enzymes show maximum activity at optimum pH.
• The enzymes are inactivated by poisons and radiation.