NCERT Exemplar Class 11 Biology Solutions Chapter 9 Biomolecules

Multiple Choice Questions:

Question:1

It is said that the elemental composition of living organisms and that of inanimate objects (like earth's crust) are similar in the sense that all the major elements are present in both. Then what would be the difference between these two groups?

Choose the correct answer from among the following: -

a. Living organisms have more gold in them than inanimate objects
b. Living organisms have more water in their body than inanimate objects
c. Living organisms have more carbon, oxygen, and hydrogen per unit mass than inanimate objects.
d. Living organisms have more calcium in them than inanimate objects.

Answer:

Option (c) is the answer.
Explanation:
Carbon, oxygen, and hydrogen constitute the main component of organic compounds. So this will be the exact clue for having more amount of carbon, oxygen and hydrogen per unit mass than an inanimate object.

Question:2

Many elements are found in living organisms, either free or the form of compounds. Which of the following is not found in living organisms?
a. Silicon
b. Magnesium
c. Iron
d. Sodium

Answer:

Solution:
Option (a) is the answer.
Explanation:
Elements other than Silicon, are all important constituents of a living organism. Living organism have a significant constituent requirement of Iron, Magnesium and Sodium.

Question:3

Aminoacids have both an amino group and a carboxyl group in their structure. Which one of the following is an amino acid?
a. Formic acid
b. Glycerol
c. Glycolic Acid
d. Glycine

Answer:

Solution:
Option (d) is the answer.
Explanation:
From the list of the amino acid, most of them end with “ine.” So, Glycine is the correct answer.

Question:4

An amino acid under certain conditions has both positive and negative charges simultaneously in the same molecule. Such a form of amino acid is called

a. Acidic form
b. Basic form
c. Aromatic form
d. Zwitterionic form

Answer:
Option (d) is the answer.
Explanation:
Going through all the options, we see that the word Zwitterionic is German form which means neutral with both negative and positive charge within it.

Question:5

Which of the following sugars have the same number of carbon as present in glucose?
a. Fructose
b. Erythrose
c. Ribulose
d. Ribose

Answer:

Option (a) is the answer.
Explanation:
Among the options, it is fructose which falls in the category of monosaccharides. In fact, glucose and fructose both fall in this category, and they have 6 atoms of carbon.

Question:6

An acid-soluble compound formed by phosphorylation of nucleoside is called:
a. Nitrogen base
b. Adenine
c. Sugar phosphate
d. Nucleotide

Answer:
Option (d) is the answer.
Explanation:
When one adds a phosphate group to a nucleoside, one gets another acid-soluble biomolecule called Nucleotide.

Question:7

When we homogenise any tissue in an acid, the acid-soluble pool represents
a. Cytoplasm
b. Cell membrane
c. Nucleus
d. Mitochondria

Answer:
Option (a) is the answer.
Explanation:
When we homogenise any tissue in acid, the acid-soluble pool it represents Cytoplasm.It is because organic compounds are found in the acid-soluble pool. Cytoplasm contains various soluble compound and hence called a soluble acid pool.

Question:8

The most abundant component of living organisms is
a. Protein
b. Water
c. Sugar
d. Nucleic acid

Answer:

Option (b) is the answer.
Explanation:
Going by constituent present in the human body, water constitutes 70% of the entire body weight.

Question:9

A homopolymer has only one type of building block called monomer repeated ‘n’ number of times. A heteropolymer has more than one type of monomer. Proteins are heteropolymers usually made of
a. 20 types of monomers
b. 40 types of monomers
c. 30 types of monomers
d. only one type of monomer

Answer:

Option (a) is the answer.
Explanation:
Going by facts, Proteins consists of 20 types of monomers

Question:10

Proteins perform many physiological functions. For example, some functions as enzymes. Which of the following represents an additional function that some proteins discharge?
a. Antibiotics
b. Pigment conferring colour to skin
c. Pigments making colours of flowers
d. Hormones

Answer:

Option (d) is the answer.
Explanation:
Antibiotics that have enzymes present do not possess any protein, but a lot of antibodies might not have protein or enzymes. Moreover, pigments are not proteins.

Question:11

Glycogen is a homopolymer made of
a. Glucose units
b. Galactose units
c. Ribose units
d. Aminoacids

Answer:
Option (a) is the answer.
Explanation:
Glycogen is a homopolymer made of Glucose units. This is because the glyo in glycose means that it is derived from glucose.

Question:12

The number of ‘ends’ in a glycogen molecule would be
a. Equal to the number of branches plus one
b. Equal to the number of branch points
c. One
d. Two, one on the left side and another on the right side

Answer:
Option (d) is the answer.
Explanation:
One should remember that the number of ‘ends’ in a glycogen molecule would be equal to the number of branches plus one.

Question:13

The primary structure of a protein molecule has
a. Two ends
b. One end
c. Three ends
d. No ends

Answer:

Option (a) is the answer.

Question:14

Which of the following reactions is not enzyme-mediated in the biological system?
a. Dissolving CO₂ in water
b. Untwining the two strands of DNA
c. Hydrolysis of sucrose
d. Formation of peptide bond

Answer:
Option (a) is the answer.

Very Short Answer Type Questions:

Question:1

Medicines are either man-made (i.e., synthetic) or obtained from living organisms like plants, bacteria, animals etc. and hence the latter are called natural products. Sometimes natural products are chemically altered by man to reduce toxicity or side effects. Write against each of the following whether they were initially obtained as a natural product or as a synthetic chemical.

a. Penicillin ___________________________
b. Sulfonamide ___________________________
c. Vitamin C ___________________________
d. Growth Hormone ___________________________

Answer:
A. Penicillin - Natural product
B. Sulfonamide- Synthetic product
C. Vitamin C - Natural product
D. Growth Hormone - Natural product

Question:2

Select an appropriate chemical bond among ester bond, glycosidic bond,peptide bond and hydrogen bond and write against each of the following.
a. Polysaccharide ___________________________
b. Protein ___________________________
c. Fat ___________________________
d. Water ___________________________

Answer:
a. Polysaccharides – Glycosidic bond
b. Protein - Peptide bond
c. Fats - Ester bond
d. Water - H-bond

Question:3

Write the name of any one amino acid, sugar, nucleotide, and fatty acid.

Answer:

Nucleotide- Adenosine

1. Amino acid- Glycine
2. Fatty acid- Oleic acid
3. Sugar- Glucose

Question:4

The reaction given below is catalysed by oxidoreductase between two substrates A and A’, complete the reaction.
A reduced + A’ oxidised

Answer:

A reduced + A’ Oxidised → A oxidised + A’reduced

Question:5

How are prosthetic groups different from co-factors?

Answer:

Enzymes are made up of a single or multiple polypeptide chains. But in several cases,there are non-protein constituents that are bound to the enzyme, they are known as co-factors, which makes the enzyme catalytically active. Co-factors can be of three types, i.e. enzymes, prosthetic groups, and metal ions.
Co-factors and prosthetic groups differ in the sense that prosthetic groups are tightly bound to the apoenzyme.

Question:6

Glycine and Alanine are different with respect to one substituent on the α - carbon. What are the other common substituent groups?

Answer:

COOH, NH 2 , and H are the common substituents in Glycine and Alanine.

Question:7

Starch, Cellulose, Glycogen, Chitin are polysaccharides found among the following. Choose the one appropriate and write against each.

a) Cotton fibre __________________________
b) Exoskeleton of cockroach __________________________
c) Liver __________________________
d) Peeled potato __________________________

Answer:

a) Cotton fibre - Cellulose
b) Exoskeleton of cockroach - Chitin
c) Liver - Glycogen
d) Peeled Potato - Starch

Short Answer Type Questions:

Question:1

Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure. These functional groups are, many of them at least, ionisable. As they are weak acids and bases in chemical nature, this ionisation is influenced by the pH of the solution. For many enzymes, activity is influenced by the surrounding pH. This is depicted in the curve below, explain.

Answer:

Explanation of this question can be summed up as below:
1. This variation triggers changes in charge of amino acid.
2. Dependence of enzyme on pH is because of the existence of charged amino acid at its active site.
3. The enzymatic activity reduces when pH is fewer than the optimal pH.

Question:2

Is rubber a primary metabolite or a secondary metabolite? Write four sentences about rubber.

Answer:

Rubber is actually a secondary metabolite because the of its unknown function in plants physiology

The following can be further said about rubber being of significance to humans: -
1. Rubber is for human commercial importance.
2. It undergoes the process of vulcanisation to be of use to humans.
3. It does not have any known function in plants, so it is called a secondary metabolite.
4. It is used for the production of various products like tyres, gloves, toys etc.

Question:3

Schematically represent primary, secondary and tertiary structures of a hypothetical polymer say for example a protein.

Answer:

Question:4

Nucleic acids exhibit secondary structure, justify with example.

Answer:

DNA and RNA are known to exist in the form of a helix. Since a long chain of polymer is arranged as a helix. And a helix is called secondary structure.

RNA forms a single- stranded helical form while DNA forms a double helix. As a helix is regarded to be a secondary structure, therefore, nucleic acids are present in the secondary structure.

Question:5

Comment on the statement “living state is a non-equilibrium steady-state to be able to perform work”.

Answer:

Metabolic reactions in a biological system, are always going on wherein influx and efflux of metabolites take place regularly. Hence it will be appropriate to state that the living state is a non-equilibrium steady state which is able to perform work.

Long Answer Type Questions:

Question:1

Formation of the enzyme-substrate complex (ES) is the first step in catalysed reactions. Describe the other steps until the formation of the product.

Answer:

The first step in catalysed reactions is the formation of the enzyme-substrate complex (ES). The further steps are described below:

1. As described above, in the first step, the substrate binds at the active site that, in turn, results in the formation of the enzyme-substrate complex.
2. The second stage is the transient stage which is the altered structure state. In the absence of enzymes, the activation energy required would have been higher. But as the enzyme is present, the reaction takes place even with less amount of energy.
3. In the final stage, which is the product formation stage, the product is formed, and the system’s potential energy reduces drastically. Then the enzyme is free to bind with other substrate.

Question:2

What are the different classes of enzymes? Explain any two with the type of reaction they catalyse.

Answer:

There are six different enzyme classes which can be categorised as Lysates, Isomerase, Oxidoreductase, Transferase, Hydrolase, and Ligase.

a) Oxidoreductase:
These enzymes assist with the process of simultaneous oxidation as well as reduction of two substrates.
S reduced + S’reduced → S oxidised + S’ oxidised

b) Hydrolases:
Hydrolysis of a molecule is facilitated by these enzymes.
Sucrose → Glucose + Fructose

Question:3

Nucleic acids exhibit secondary structure. Describe through Watson Crick Model.

Answer:

It is known that DNA and RNA exist in the form of a helix. Since a long chain of polymer is arranged as a helix. And a helix is called secondary structure. RNA forms a single-stranded helical form while DNA forms a double helix. It is known that helix is regarded as a secondary structure; thus, in secondary structure, nucleic acids exist.

Arranged in a double helix, two polypeptide chains make up the DNA. Nitrogenous bases are present towards the inner side in the DNA while the backbone is made up of sugar-phosphate. The nitrogenous bases connect with each other through H bonds.This H bond provides stability to the helix.

Question:4

What is the difference between a nucleotide and nucleoside? Give two examples of each with their structure.

Answer:

The difference between a nucleotide and nucleoside can be described as below:
Talking about Nucleotides, they are formed of nucleoside and phosphate group and are the monomers of nucleic acid. As a matter of fact, nucleosides are the constituent of nucleotides. Some examples of nucleosides are guanosine, thymidine, adenosine, uridine and cytidine. Some examples of nucleotides are guanylic acid, uridylic acid adenylic acid, thymidylic acid, and cacodylic acid.

Question:5

Describe various forms of lipid with a few examples.

Answer:

Lipids are classified into three categories:
1. Simple lipids: - Simple lipids are the esters of fatty acids and can be further divided into: -

- Waxes: - Esters of high fatty acids with alcohol.
- Fats: - Eaters of higher fatty acids with glycerol.
For example Triglycerol etc.
2. Compound lipids: - Compound lipids are those lipids that contain other groups as well in addition to alcohol and glycerol. They can be further categorised into: -

1. Sphingo Lipids
2. Glycerophospholids
3. Glycolipids

For example: Cephalin, Gangliosides etc.

3. Derivatives lipids: - When lipids consist of hydrocarbon ring and the long chain of hydrocarbons they are called derivatives
For Examples: Steroids, Cholesterol etc.