Class 11 Biology Chapter 9 Biomolecules

Key Concept: Activation Energy

b) They lower the activation energy, making it easier for the reaction to proceed.

[Solution Description] Enzymes are catalysts that function by lowering the activation energy of a reaction. This means they reduce the amount of energy needed for reactants to form the transition state, thus accelerating the reaction rate without being consumed in the process.

Key Concept: Complex Composition

c) N-acetyl galactosamine

[Solution Description] N-acetyl galactosamine is a chemically modified sugar often found in mucopolysaccharides and glycoproteins. It has an acetyl group attached to nitrogen.

Key Concept: Basic Components

d) Glycerol

[Solution Description] Triglycerides are composed of glycerol and three fatty acids. Glycerol acts as the backbone to which the fatty acids are attached through ester bonds.

Key Concept: Elemental Comparison

d) Carbon

[Solution Description] In living organisms, carbon is significantly more abundant than in non-living matter like the earth’s crust. Carbon forms the backbone of all organic molecules, making it essential for life.

Key Concept: Function of Nucleic Acids

c) Genetic information storage

[Solution Description] Nucleic acids primarily serve as genetic material, storing and transmitting hereditary information necessary for growth, development, functioning, and reproduction.

Key Concept: Fraction Separation

d) Filtrate

[Solution Description] The process of grinding living tissues in trichloroacetic acid leads to the separation into two fractions; the liquid part that passes through is called the filtrate.

Key Concept: Definition Recall

b) Morphine

[Solution Description] Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of organisms. Examples include morphine, curcumin, and vinblastin.

Key Concept: Reaction Type Identification

c) Removal of groups forming double bonds

[Solution Description] Lyases are involved in reactions that result in the formation of double bonds upon removing groups from substrates.

Key Concept: Enzyme Classification

c) Transferases

[Solution Description] Transferases are the class of enzymes that catalyze the transfer of functional groups other than hydrogen from one molecule to another. This is a key characteristic that defines this group of enzymes.

Key Concept: Source Identification

b), Plants

[Solution Description] Essential oils are concentrated plant extracts that retain the natural smell and flavor of their source. They are commonly derived from plants such as lemon grass.

Key Concept: Common Examples

b) Glycogen

[Solution Description] Glycogen is the polysaccharide responsible for energy storage in animals. It is similar to starch in plants but has a more highly branched structure, which allows for rapid release of glucose.

Key Concept: Role of Water in Hydrolysis

d) Acts as a reactant

[Solution Description] In a hydrolysis reaction catalyzed by hydrolases, water acts as a reactant that splits the substrate molecule into smaller parts, often resulting in the cleavage of a specific bond.

Key Concept: Enzyme Classes

d) Ligases

[Solution Description] Ligases are the class of enzymes responsible for catalyzing the joining of two molecules or compounds. This process involves forming new bonds and is crucial in various biological processes such as DNA synthesis.

Key Concept: Elemental Comparison

d) Carbon

[Solution Description] The main elements present in the human body are oxygen, carbon, hydrogen, and nitrogen. In the earth’s crust, silicon and aluminum are more abundant. Among these, carbon is significantly more abundant in living organisms such as humans than in the earth’s crust.

Key Concept: Basic Definition

c) Catalyze inter-conversion of isomers

[Solution Description] Isomerases are enzymes that catalyze the inter-conversion of isomers, which includes changing the structure or position of molecules but not their molecular formula.

Key Concept: Enzyme Components

a) Apoenzyme

[Solution Description] The part of the enzyme that binds to the substrate is called the active site, which is part of the apoenzyme, the protein portion of the enzyme.

Key Concept: Basic Definition

c) Amino acids

[Solution Description] Primary metabolites are involved in normal physiological processes and include amino acids and sugars, which are found in animal tissues.

Key Concept: Protein Structure

d) Amino acids

[Solution Description] Proteins are composed of amino acids linked together by peptide bonds.

Key Concept: Structure Levels

a) Primary structure

[Solution Description] The primary structure of a protein is characterized by its unique sequence of amino acids, which are linked together in a chain.

Key Concept: Base Classification

c) Thymine

[Solution Description] Cytosine, thymine, and uracil are pyrimidines. These bases have a single-ring structure, differing from purines like adenine and guanine, which have a double-ring structure.

Key Concept: Function Identification

b) Energy storage

[Solution Description] Glycogen serves as an energy storage molecule in animals, with glucose units that can be rapidly mobilized to meet sudden energy demands.

Key Concept: Storage Function

c) Starch

[Solution Description] Starch is the primary polysaccharide used by plants to store energy. It consists of two components: amylose, which forms a helical structure, and amylopectin. Both these components are made from alpha-glucose units.

Key Concept: Sugar Type

c) Deoxyribose

[Solution Description] DNA contains deoxyribose sugar as its component. In contrast, RNA contains ribose sugar. Therefore, the correct sugar type for DNA is deoxyribose.

Key Concept: Enzyme Inhibition

d) Competitive inhibitor

[Solution Description] Competitive inhibitors resemble the substrate and compete directly for the active site, preventing substrate binding.

Key Concept: Co-factor Interaction, Metal Ion Specificity

b) The enzyme’s active site collapses, losing all catalytic activity.

[Solution Description] Zinc ions play a pivotal role in stabilizing the active site of carboxypeptidase and facilitating substrate binding through coordination bonds. Removing zinc distorts the active site, leading to loss of structural integrity. Consequently, the enzyme cannot efficiently catalyze peptide bond hydrolysis, effectively rendering it inactive.

Key Concept: Organic Compounds

d) Glucose

[Solution Description] Glucose is a simple sugar and a vital organic compound that is present widely in various forms within living organisms. It serves as an essential source of energy through cellular respiration.

Key Concept: Basic Definition

c) To catalyze oxidation-reduction reactions

[Solution Description] Oxidoreductases are enzymes that catalyze oxidation-reduction reactions, where one substrate is oxidized and another is reduced.

Key Concept: Molecular Weight Comparison

b) Macromolecules have molecular weights more than 10,000 Da.

[Solution Description] Macromolecules have a molecular weight greater than 10,000 Da. They are large biomolecules that include proteins, nucleic acids, and polysaccharides.

Key Concept: Protein Folding Dynamics, Subunit Interaction

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] For a protein to function properly, it must fold into its correct three-dimensional shape, which allows for specific interactions between subunits necessary for assembling the quaternary structure. While the sequence of amino acids (primary structure) influences the initial protein folding, it does not solely determine the interactions in quaternary structures. Other factors such as environmental conditions and post-translational modifications also play significant roles in facilitating these interactions. As a result, while both statements have elements of truth, the Reason does not accurately explain the Assertion.

Key Concept: Activation Energy

c) They lower the activation energy needed for the reaction.

[Solution Description]

Enzymes act as catalysts that lower the activation energy required for a reaction, thus speeding up the process without being consumed by it.

Key Concept: Primary vs Secondary

c) Alkaloids

[Solution Description] Secondary metabolites are compounds that are not directly involved in the normal growth, development, or reproduction of an organism. They often have ecological roles such as defense mechanisms and can include substances like alkaloids and flavonoids.

Key Concept: Component Identification

b) Proteins

[Solution Description] Proteins are polymers made up of amino acids and they form part of the acid-insoluble fraction. Lipids, water, and sodium are not considered polymeric substances.

Key Concept: Elemental Comparison

c) Carbon

[Solution Description] Living organisms primarily contain carbon, hydrogen, and oxygen, with carbon being significantly more abundant than in non-living matter.

Key Concept: Enzyme Stability

c) 80°-90°C

[Solution Description] Enzymes from thermophilic organisms remain stable and functional at high temperatures typically between 80°-90°C.

Key Concept: Enzyme Function

b) They increase the reaction rate.

[Solution Description] Enzymes act as catalysts to increase the rate of chemical reactions by lowering the activation energy required.

Key Concept: Enzyme Stability

d) They become more stable

[Solution Description] Enzymes from thermophilic organisms are adapted to function and remain stable at high temperatures, such as those around 80°-90°C, without denaturing or losing activity.

Key Concept: Element Comparison

c) Carbon

[Solution Description]

In living organisms, carbon is one of the primary elements that is far more abundant than in most inorganic or non-living matter. Carbon forms the backbone of organic molecules such as proteins, lipids, and nucleic acids.

Key Concept: Elemental Comparison

c) Carbon

[Solution Description] The human body has a higher percentage of carbon compared to the earth’s crust. Carbon is essential for forming organic compounds and plays a significant role in cellular structures and functions.

Key Concept: Structure-Function Relationship

c) Tertiary Structure

[Solution Description] The tertiary structure refers to the three-dimensional folding of a protein, which determines its functional properties. This level of structure is crucial because it dictates how the protein interacts with other molecules.

Key Concept: End Identification

b) Non-reducing end

[Solution Description]

The left end of a polysaccharide chain is termed the non-reducing end. It is opposite to the reducing end, which is at the right side of the chain.

Key Concept: Protein and Disease, Protein Structural Hierarchy

d) Aggregation from misfolding can cause conditions like Alzheimer’s by disrupting cellular pathways.

[Solution Description] Misfolding disrupts normal protein functions, forming aggregates that interfere with cell processes. For example, in neurodegenerative diseases, such aggregates block cellular pathways or form toxic species leading to cell death. Proper folding is crucial, as errors at any structural level—primary to quaternary—can propagate to malfunction and pathology.

Key Concept: Basic Concepts

a) Proteins, nucleic acids, polysaccharides, and lipids

[Solution Description] The acid-insoluble fraction typically includes macromolecules such as proteins, nucleic acids, polysaccharides, and lipids. These molecules are characterized by their large size and insolubility in water.

Key Concept: Basic Composition

d) All of the above

[Solution Description] The acid-insoluble fraction includes proteins, nucleic acids, polysaccharides, and lipids, according to the syllabus.

Key Concept: Base Pairing

c) Guanine

[Solution Description] In DNA, cytosine pairs with guanine through three hydrogen bonds as per base pairing rules.

Key Concept: Saturation Explanation

a) All enzyme active sites are occupied

[Solution Description] The reaction velocity reaches a maximum (Vmax) because all enzyme active sites are occupied. Once all enzymes are saturated with substrate molecules, there are no free enzyme molecules available to bind additional substrate, thus limiting the reaction velocity.

Key Concept: Base Classification

c) Adenine

[Solution Description] Purines are nitrogenous bases with a double-ring structure. In nucleic acids, the two purine bases are adenine and guanine.

Key Concept: Enzyme Classification

d) Transferases

[Solution Description] Enzymes are divided into six major classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Transferases belong to their own class due to their unique function of transferring groups.

Key Concept: Substrate Concentration

d) It increases and then levels off

[Solution Description] As substrate concentration increases, the rate of reaction initially increases because more substrate molecules are available to bind with enzyme active sites. However, once all the active sites are occupied (saturation point), the reaction rate levels off and reaches Vmax.

Key Concept: Structural Analysis, Real-world Application

d) Active site conformation

[Solution Description] The active site conformation is integral to an enzyme’s substrate specificity and efficiency. Alterations here can drastically affect how well the substrate fits and how efficient the catalysis proceeds. While the hydrophobic core, surface charge distribution, and substrate binding loop play roles, they don’t have as profound an impact on both specificity and catalytic efficiency simultaneously compared to the active site.

Key Concept: Basic Definitions

d) Ten thousand daltons and above

[Solution Description] Macromolecules have molecular weights in the range of ten thousand daltons and above.

Key Concept: Nucleic Acid Components

b) Monosaccharide

[Solution Description] A nucleotide consists of a heterocyclic compound known as a nitrogenous base, a sugar (monosaccharide), and a phosphate group.

Key Concept: Basic Definition

a) Compounds with known physiological roles

[Solution Description] Primary metabolites are compounds that have a direct role in the normal growth, development, and reproduction of living organisms.