Important Questions Class 11 Biology Chapter 9

Important Questions Class 11 Biology Chapter 9: Biomolecules

Biology is a subject that helps study the multidisciplinary phenomena of the world around us and its constituents. Biology Chapter 9 of Class 11 is about Biomolecules. Understanding Biomolecules is a key fundamental concept in the scientific concepts of Biology. Biomolecules are the primary building blocks of living organisms and are important for the right functioning. They promote the biological processes necessary for life and vary in structure and size. They support growth, sustainability as well as reproduction in organisms. Biomolecules primarily consist of hydrogen and oxygen. Some key topics explained in this chapter include proteins, carbohydrates, nucleic acids, and lipids. 

In our question bank of Important Questions Class 11 Biology Chapter 9,  comprises questions that Extramarks experts have collated with questions and answers about all the main topics of the chapter Biomolecules. These questions are based on the key concepts and the definitions covered. These key concepts give students a clear understanding of each concept they have learnt and thus retain their learning for a much longer period of time. As a result of understanding better and retaining a lot of content, students develop a very good command of the subject and thus score very well in their examinations.

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Biomolecules Class 11 Questions and Answers

Our subject matter experts believe students must practise questions to write quick and concise  answers. For this purpose, they have prepared Class 11 Biology Chapter 9 Important Questions. They have collated these questions from NCERT textbooks, CBSE sample papers and reference books. Apart from it, they have also written the answers following the CBSE guidelines. The Important Questions Class 11 Chapter 7 include all the possible questions from this chapter. 

A few of the important questions and their answers from our question bank are as follows:

Q1. What are monosaccharides? Give examples.

Answer 1 

Monosaccharides are the simplest carbohydrates molecules that cannot be hydrolysed into smaller carbohydrates molecules. The general formula of carbohydrates is Cn H2n OH; their examples are Ribose, Glucose and Fructose.

Q 2. What is a disaccharide?  Write briefly.

Answer 2- 

1. A sugar molecule composed of two monosaccharide molecules is referred to as a  disaccharide; e.g. one molecule each of glucose and fructose dehydrated together forms a disaccharide.

Q3. Why do fats release more energy than carbohydrates in the oxidation process?

Answer 3- 

Like carbohydrates, fats are also made up of Carbon, Hydrogen, and Oxygen. Still, as they contain fewer oxygen molecules than carbohydrates, so on oxidation, they consume more oxygen releasing extra energy.

Q4. What is the function of calcium ions in our human body? In what form are calcium ions deposited in the middle lamella of our body?

Answer 4- 

Calcium is impregnated in bones and teeth, which provides them with strength and rigidity. It is also deposited in the middle lamella in the form of calcium pectate.

Q5. Explain how the glycosidic bonds are made.

Answer 5- 

Formation of the Glycosidic Bonds: A monosaccharide’s aldehyde or ketone group reacts and binds with an alcoholic group of anotherorganic compound to join the two compounds. This bond is known as the glycosidic bond, and this bond may be hydrolysed to give the original compounds. Monosaccharides are also united through glycosidic bonds that give rise to compound carbohydrates.

Q6. Describe the different functions of polysaccharides in living organisms.

Answer 6- 

Polysaccharides have many different types of functions which can be classified as – 

Food storage polysaccharides: As the name suggests, these are the type of saccharides that store food. Common examples of food-storing polysaccharides are starch and glycogen.

1. Starch: It is formed as a product of the photosynthesis process. It is found in large quantities in edible items like rice, wheat, cereals, legumes, potato, tapioca, and bananas. It is the major energy-giving substance as it performs the storage of food.
2. Glycogen: It is present in mammals’ muscles and liver that store energy. They also contain the distinct advantages of storing carbohydrates in the form of polysaccharides.

During the formation of polysaccharides, many molecules of water are removed, and the bulk is reduced. 

Polysaccharides are relatively easy to store and easily break down by many enzymes to release energy.

Structural Polysaccharides: These contain the polysaccharides responsible for an organism’s formation. They contain cellulose and chitin. 

1. Cellulose: It is specifically a plant product and the most abundant material found in the living world. It forms the cell walls and is a fibrous polysaccharide containing high tensile strength. Substances like wood and cotton have large quantities of cellulose.
2. Chitin: Chitin is distinctly like cellulose in many ways. The only exception is that its basic unit is not glucose but a similar molecule called N-acetyl glucosamine that contains nitrogen. Chitin is a soft and leathery substance that becomes hard when filled with calcium carbonate or certain proteins. Chitin is insoluble in water which helps it retain its form. The retaining of its form also helps in strengthening the structure of organisms.

Q7. Explain in brief the tertiary structure of proteins.

Answer 7- 

The tertiary structure of proteins contains many amino acid units that form polypeptides. The peptide bonds hold the amino acids together in a particular way, constituting the protein molecules’ primary structure. A functional protein is described as a protein that contains one or more polypeptide chains.

Through the formation of hydrogen bonds, the peptide chains assume a secondary structure where the secondary protein may be in the form of a twisted helical structure or a pleated sheet structure.

When the individual peptide chains made of amino acids of the secondary structure of the protein are further coiled and folded into sphere-like structures with the hydrogen bonds between the amino and carboxyl group, cross-linking on-chain to another occurs as they form the tertiary structure.

Also, the ability of proteins to carry out specific reactions depends on their primary, secondary, and tertiary structure.

Q8. Describe phospholipid. Describe their arrangement in the cell membrane.

Answer 8- 

Phospholipids: Phospholipids are classified as a class of lipids that serve as the backbone of the structural component of the cell membrane. Phospholipids contain only two fatty acids, which are attached to the glycerol, while the third glycerol binding site holds a phosphate group. This phosphate group is bound to the alcohol.

These lipids have both hydrophilic and hydrophobic units due to a charge on a molecule’s phosphoric acid or alcohol head and lack of a charge on the long tail of the molecule, which is made of fatty acids. When exposed to an aqueous solution, these charged heads are attracted to the water phase, while the non-polar tails are repelled from the water phase.

Phospholipids- 

Phospholipids are when the two layers of the polar lipids come together to form a double layer. The outer hydrophilic face of every single layer of the phospholipids orients itself towards the solution, through which the hydrophobic part becomes immersed in the core of the bilayer structure.

Also, water acts as a solvent for polar molecules, and the arrangement of phospholipids in the lipid bilayer of membranes depends on water.

Q9. Classify the following terms into one of the appropriate glycosidic, ester, peptide, and hydrogen bonds.

The terms are –

1. a) Polysaccharide b) Protein c) Fat and d) Water

A.2. a) Polysaccharide – glycosidic bond

1. b) Protein-peptide bond
2. c) Fat–ester bond
3. d) Water – hydrogen bond

Q10. Explain why nucleic acids display a secondary structure.

Answer 10. 

The secondary structure of nucleic acid molecules is in the context of base-pairing interactions of a single molecule or a group of interacting molecules. The secondary structure of RNA and DNA varies respectfully. For example, the secondary structure of deoxyribonucleic acid consists of two complementary strands of polydeoxyribonucleotide that are highly coiled on a common axis forming a helical structure. This double-stranded helical structure of the deoxyribonucleic acid is supported by phosphodiester bonds, ionic interactions, and hydrogen bonds.

Q11. Describe the living state briefly as a non-equilibrium steady state. 

Answer 11 

The most important fact of the biological systems is that all living organisms exist in a steady state characterised by concentrations of each of the following biomolecules. These biomolecules are in a metabolic flux where any chemical or physical process moves spontaneously to equilibrium. The steady state of the biomolecules is a non-equilibrium state where one should remember that systems at the equilibrium cannot perform work. Also, as living organisms work continuously, they cannot afford to reach the equilibrium state. Thus, the living state is in a non-equilibrium steady-state to be able to perform work that is attained via energy provided by metabolism.

Q12.What are the main functions of carbohydrates?

Answer 12- 

The major functions of carbohydrates are:

Regulation of the blood glucose level.

Involved in the metabolism of fat and prevents ketosis.

Provide energy and food to the body and the nervous system.

Functions are the basic food component, including fibre, starch, and sugars.

They are the primary source of energy. Therefore, it is involved in the breakdown of starch into glucose and proteins to produce energy for metabolism.

Q13. What are amino acids?

Answer 13-

 As the name suggests,  amino acids contain an amino group and a carboxyl group, both in their structure. Also, all naturally occurring amino acids usually found in proteins are called L-amino acids. 

Q14. Guess from which of the following compounds the simplest amino acid is made of?

(a) Formic acid 

(b) Methane

 (c) Phenol acid

 (d) Glycine

Ans: Option (d) is the right answer. 

Explanation – Glycine is an amino acid (which has both an amino group and a carboxyl group in its structure).

Q14. Enzymes are bio catalysts in nature. They catalyse major biochemical reactions. In general, they also reduce the activation energy of reactions. Many of the physicochemical processes are enzyme-mediated. Some examples of enzyme-mediated reactions are given below. Explain the wrong answer.

(a) Dissolving Carbon dioxide in water

(b) Unwinding the two strands of the DNA.

(c) Process of hydrolysis of sucrose 

(d) Formation of the peptide bond

Ans: Option (a) is the right answer.

Explanation- Dissolving Carbon dioxide in water is a physical process.

Q15.Comment on the following statement “living state is a non-equilibrium steady state that can perform work”.

Answer 15- 

The most important fact of the biological systems is that all living organisms exist in a steady state characterised by concentrations of each of the following biomolecules. These biomolecules are in a metabolic flux where any chemical or physical process moves spontaneously to equilibrium. The steady state of the biomolecules is a non-equilibrium state where one should remember that systems at the equilibrium cannot perform work. Also, as living organisms work continuously, they cannot afford to reach the equilibrium state. Hence the living state is also a non-equilibrium steady state that can perform work; the living process is a constant effort to prevent it from falling into equilibrium. The energy input also achieves this. The metabolism process also provides a mechanism for the generation of energy. Hence the living state and the metabolism are synonymous. Without metabolism, there can’t be a living state.

Q16. Nucleic acids exhibit a secondary structure, so describe it through the Watson-Crick Model.

Answer 16- 

Nucleic acids exhibit a wide variety of secondary structures. For example, one of the major secondary structures exhibited by acid is the famous Watson- Crick model which states that Deoxyribonucleic acid exists as a double helix. This model further states that the two strands of the polynucleotides are antiparallel, i.e., they run in the opposite direction. Also, the backbone is formed by the sugar-phosphate and the sugar chain. The nitrogen bases present in them are projected perpendicular to the backbone of the DNA. The A and G nitrogenous bases of one strand compulsorily base pairs with T and C bases on the other strand. Two hydrogen bonds are present between the A and T bonds, and three are present between the G and C bonds. Each strand appears like a spiral staircase. Where a pair of bases represent each step of the ascent. Also, the strand turns 36° degrees at each step of the ascent. 

One full turn (360*) of the helical strand involves around ten steps or ten base pairs. The pitch of the DNA is 34 A, where the rise per base pair would be 3.4 A. This form of DNA with the stated above are B-DNA’s salient features.

Q17. Formation of the enzyme-substrate complex called ES complex is the starting step in catalysed reactions. Describe the other steps that form the product briefly.

Answer 17- 

The catalytic cycle of enzyme action is described in the following steps:

(1) In the first step, the substrate binds to the enzyme’s active site and fits into the active site.

(2) The binding of the substrate then induces the enzyme to alter its shape, which results in the fitting of the enzyme more tightly around the substrate.

(3) The active site of the enzyme, which is now near the substrate, breaks the chemical bonds of the substrate, and the following enzyme-product complex is generated.

(4) The enzyme releases the products of the reaction, and then the free enzyme is ready to bind to another molecule of the substrate and run through the catalytic cycle once again.

Q18. Describe starch, cellulose, and phospholipids briefly.

Answer 18- 

Chitin: Chitin is distinctly like cellulose in many ways. The only exception is that its basic unit is not glucose but a similar molecule called N-acetyl glucosamine that contains nitrogen. Chitin is a soft and leathery substance that becomes hard when filled with calcium carbonate or certain proteins. Chitin is insoluble in water which helps it retain its form. The retaining of its form also helps in strengthening the structure of organisms.

Starch: It is formed as a product of the photosynthesis process. It is found in large quantities in edible items like rice, wheat, cereals, legumes, potato, tapioca, and bananas. It is the major energy-giving substance as it performs the storage of food.

Phospholipids- 

Phospholipids are when the two layers of the polar lipids come together to form a double layer. The outer hydrophilic face of every single layer of the phospholipids orients itself towards the solution, through which the hydrophobic part becomes immersed in the core of the bilayer structure.

When exposed to an aqueous solution, these charged heads are attracted to the water phase, while the non-polar tails are repelled from the water phase.

Q 19. What are Esters?

Answer 19. Esters, in biology, refer to an organic molecules generated after a combination of an acid with an alcohol. The process is done by removing water from both elements and is generally known as ‘esterification’. Esters are commonly found everywhere and may be used as fragrances with low molecular weight. They are also added to essential oils.

Q 20. What are essential fatty acids?

Answer 20. Essential fatty acids are the fatty acids that must be consumed as the body needs them to maintain good health and for biological processes; however, it cannot synthesise them. These do not include fats that serve as fuel only. They are called essential, as the body cannot produce them on its own, and they must be consumed as a part of the diet and are key to the right functioning of the body.

Q 21. What is the role of biomolecules in the diagnosis of diseases?

Answer 21. . Biomolecules are vital in all life processes and activities, including the process of disease development. Hence, accurately detecting biomolecules is important in diagnosing diseases and therapy.

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Following are some of the benefits for students to practise from Extramarks NCERT curriculum-based Important Questions Class 11 Biology Chapter 9:

• The important Question Class 11 Biology Chapter 9 are based on the NCERT book while adhering to the CBSE’s latest curriculum.
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• Questions are covered from all the major topics of the chapter, ensuring no topic has been spared. Subject matter experts have prepared these important questions with years of experience to provide the students with a smooth and deep learning experience so that they do not need to look elsewhere for any assistance. 
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