NCERT Solutions For Class 11 Biology Chapter 9 - Biomolecules

Q1. What are macromolecules? Give examples.

Answer:

The complex high molecular weight molecules separated in acid-insoluble fractions in the presence of trichloroacetic acid are referred to as macromolecules. They are polymers of a molecular weight of 10,000 daltons and above. Proteins, carbohydrates, nucleic acids, etc., are macromolecules. There are lipids in the acid-insoluble fraction, too, but they are not of high molecular weight.

Q2. Illustrate a glycosidic, peptide, and a phosphodiester bond.

Answer:

Glycosidic bond- This bond is formed between the 1st carbon atom of one monosaccharide and 4 carbon atom of a neighbouring monosaccharide unit. During the formation of this bond, a water molecule is released. A representation of a glycosidic bond is as follows

Peptide bond- This is a covalent bond formed between the carboxyl group of one amino acid and the amino group of neighbouring amino acids. A water molecule is released in the formation of a peptide bond. A representation of a peptide bond is as follows

Phosphodiester bond- It refers to the phosphate-hydroxyl linkage between two nucleotides. In this bond, the phosphate attached to the hydroxyl group at the 5' carbon of the pentose sugar is, in turn, bonded to the hydroxyl group of the 3' carbon of the pentose sugar of the next nucleotide.

Q3. What is meant by the tertiary structure of proteins?

Answer:

The three-dimensional configuration of a protein that arises from repeated coiling and folding of helical and pleated polypeptide chains is termed its tertiary structure. Through repeated folding and coiling, polar side chains remain exposed, whereas non-polar amino acids are kept inside. The tertiary structure is bonded through weak bonds. The activity of a protein exists in tertiary structures.

Q4. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry that manufactures the compounds by isolation. Find out who are the buyers.

Answer:

The structures of 10 small molecular weight biomolecules are as follows.

These biomolecules are manufactured in biotechnology industries.

Q5. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., Cosmetics, etc.)

Answer:

Proteins with therapeutic uses are insulin, oxytocin, ADH, thrombin, fibrinogen, renin, immunoglobulin, diastase, streptokinase, etc.

Other applications of proteins are

1. As cosmetics- Proteins such as casein are used in beauty creams, shampoos, etc.

2. Sweeteners- Thaumatin and monellin are sweet proteins.

3. Dietary supplements- Proteins can be used as dietary supplements.

Q6. Explain the composition of triglyceride.

Answer:

A triglyceride is a chemical formed by the esterification of three molecules of fatty acids with one molecule of trihydric alcohol called glycerol. All three fatty acids of triglyceride can be similar, as in tripalmitin, or dissimilar, as in palmito-oleoistearin, dipalmitostearin, etc.

Q7. Can you describe what happens when milk is converted into curd or yoghurt, from your understanding of proteins?

Answer:

Milk has a protein known as casein. When we mix a little curd into milk, the protein casein is coagulated by the action of lactic acid bacteria, and thus milk is transformed into curd. Coagulation breaks the structure of the protein casein.

Q8. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models).

Answer:

Yes, we can try constructing models of biomolecules with the help of commercially purchased atomic models, like ball and stick models. The stick is, in the model, taken to be a bond, and balls of varying colours are taken to be atoms.

Q9. Attempt to titrate an amino acid against a weak base and discover the number of dissociating ( ionizable ) functional groups in the amino acid.

Answer:

When we titrate an amino acid against a weak base, it dissociates into its functional groups, i.e., -COOH (carboxylic group) and -NH (amino group)

Q10. Draw the structure of the amino acid, alanine.

Answer:

The structure of the amino acid alanine is represented below:

Q11. Find out a qualitative test for proteins, fats and oils, and amino acids, and test any fruit juice, saliva, sweat, and urine for them.

Answer:

One of the qualitative tests for proteins is the xanthoproteic test. When a qualitative test for protein in urine is done using the aid of the xanthoproteic test, if a yellow precipitate is formed, then it is guaranteed that there is protein in it. The qualitative test for fats is the emulsification test.

During the emulsification test, the experimental material is first treated with ethanol and then dissolved in water. The development of an emulsion proves the existence of fats. The qualitative analysis for oils is the paper test. The material to be tested is placed on paper. The presence of oil is established when oil marks remain.

Q12. Find out how much cellulose is made by all the plants in the biosphere and compare it with how much paper is manufactured by man, and hence what the consumption of plant material by man is annually. What a loss of vegetation!

Answer:

Paper consists of wood pulp, which is predominantly composed of cellulose. Cellulose is a polymer of glucose molecules. Approximately 85 billion tonnes of cellulose are generated every year in the biosphere. Paper production requires 0.5 billion tonnes of wood. The rise in the usage of wood has caused immense loss of vegetation.