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NCERT · Class 11 · Biology

Chapter 9: Biomolecules

Practice each question, then open the answer or worked solution.

Textbook exercises

11 questions
Q1Written answer

What are macromolecules? Give examples?

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Ans:  Chemical compounds, which are found in the acid-insoluble fraction are called macromolecules or biomacromolecules. As suggestive of its name, its molecular weights lie above \[1000\] Dalton. Consequently, micro molecules have molecular weights of less than \[1000\] Daltons. 

Examples of macromolecules are—proteins, lipids, and carbohydrates, etc. Except for lipids, all the other macromolecules including carbohydrates, proteins, and nucleic acids are polymeric substances.


Q2Written answer

What is meant by the tertiary structure of proteins?

Tertiary structure of proteins refers to the folding of a single polypeptide chain into a specific shape that determines the function of protein.



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Solution coming soon.

Q3Written answer

Find and write down structures of ten fascinating small molecular weight biomolecules. Find there is any industry that produces the compounds by isolation. Find out who the buyers are.

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Ans:  The structures of ten different small molecular weight biomolecules are given below.

Glucose:




Fructose:




Cholesterol:




Ribose:




Deoxyribose:




Tyrosine:




Tryptophan:




Melatonin:




Adenine:




Guanine:




Many industries manufacture compounds by the process of isolation. Some examples are given below.

Industry

Compounds

Buyer

Pharmaceuticals manufacturing industries

Enzymes

Agriculture based food industries, such as companies manufacturing juices, jams, etc., research institutes, cosmetics, medicine companies, paper industry, clothing industry, etc.

The liquid glucose manufacturing industry

Liquid Glucose

Food companies, Drug and pharmaceutical companies.


Q4Written answer

Find out and create a list of proteins utilized as therapeutic agents. List additional uses of proteins (e.g., cosmetics, etc.)

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Ans: A list of proteins used as therapeutic agents are given below.

Proteins

Therapeutic Use

  1. Insulin

Diabetes

  1. Vasopressin

Treatment of diabetes insipidus.

  1. Interleukin II

Used to prevent low platelets counts and to

decrease the requirement for blood transfusions following cancer treatments.

  1. Oxytocin

Used for inducing uterine contractions to induce labour during pregnancy.


  • Both plants and animals give the appropriate proteinaceous materials for the preparation of cosmetic items. Proteins from algae and fungi, though, are also increasingly being utilized as protein sources.

  • High-protein plants most widely used as beginning material for making vegetable proteins are wheat and corn gluten, rice, soy, and oat protein concentrates, and defatted oilseeds (almond, peanuts, sunflower). Among the larger variety of vegetable proteins, soy globulins and wheat gluten are by far of the widest use. Wheat gluten (often just known as wheat protein) is a distinctive cereal protein of high elasticity when hydrated. Soy proteins are useful because of their thickening and emulsifying effects.

Q5Written answer

Explain the composition of triglyceride.

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Ans: Triglycerides are a type of lipids found in living beings, that are synthesised due to the esterification of three fatty acids with a glycerol molecule. These are also called fats and oils based on their melting points.



Oils have lower melting points as compared to fats. The three fatty acids may be different or the same. Therefore, they may be known as simple or mixed.


Q6Written answer

Can you try the structure of biomolecules utilizing commercially available atomic models (Ball and stick models).

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Ans: Yes, we can create models of biomolecules using commercially available atomic models.



Q7Written answer

Draw the structure of the amino acid alanine.

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Ans: The structure of alanine is given below.



Q8Written answer

What are gums made of? Is fevicol different?

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Ans: Gums are made up of carbohydrates and chemically they are heteropolysaccharides. 

Fevicol is polyvinyl alcohol glue. It is different from natural gums as it is a synthetic product.

Q9Written answer

Find out a qualitative test for proteins, fats and oils, and starch amino acids and test any fruit juice, saliva, sweat, and urine for them.

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Ans:

i. A qualitative test for proteins: Xanthoproteic test

Experimental Material

Observation

Inference

(a) Urine

Yellow precipitate

The formation of yellow precipitate suggests the presence of protein in the food material

(b) Water

No precipitate


ii. A qualitative test for fats: Emulsification test

Experimental Material

Observation

Inference

(a) Sweat

Oil droplets

Formation of oil droplets

i.e., emulsification signifies the presence of fats in the provided food material.

(b) Water

No oil droplet


iii. A qualitative test for oils: Paper test

Experimental Material

Observation

Inference

(a) Food material (sample) 

Paper turns into a Translucent

Opaque paper becomes translucent which suggests the presence of fats in the food material

(b) Water

Paper gets soggy


iv. A qualitative test for starch: Iodine test

Experimental Material

Observation

Inference

  1. Fruit juices

Blue-black colour when few drops of iodine are added.

The formation of blue-black colour suggests the presence of starch in the provided food material.

  1. Water

No change in colour 

Q10Written answer


Find out exactly how much cellulose is produced by the plants in the biosphere and then compare it to how much paper is produced by human beings and therefore, what is the use of plant material by man each year. What a loss of vegetation?

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Ans: Most paper is formed from wood pulp. The major component of wood pulp is cellulose, a polymer made of several glucose molecules linked together. The cellulose molecules and their bonding to each other give the paper its properties. Nearly \[33\% \] of everything in the plant matter is cellulose. The cellulose content of wood is \[40 - 50\% \]and that of cotton is\[90\% \]. For industrial use, cellulose is mostly obtained from cotton and wood pulp. It is used primarily to produce paper and paperboard; to a smaller extent. It is converted into a large variety of derivative products like rayon and cellophane.