Question 1

How does a competitive inhibitor affect enzyme activity?

Accepted Answer

Correct Option: B. Solution: A competitive inhibitor resembles the substrate and competes for binding at the enzyme's active site, thereby reducing enzyme activity.

Question 2

Which of the following is a component of the acid-insoluble fraction of living tissues?

Accepted Answer

Correct Option: B. Solution: Proteins are part of the acid-insoluble fraction, which includes macromolecules with high molecular weights.

Question 3

What happens to enzyme activity when the temperature exceeds the optimum level?

Accepted Answer

Correct Option: C. Solution: Enzyme activity decreases when the temperature exceeds the optimum level because high temperatures can denature proteins, including enzymes.

Question 4

Which factor does NOT affect enzyme activity?

Accepted Answer

Correct Option: D. Solution: Enzyme activity is affected by temperature, pH, and substrate concentration, but not by the color of the enzyme.

Question 5

Which statement correctly describes the zwitterionic form of amino acids?

Accepted Answer

Correct Option: A. Solution: The zwitterionic form of amino acids occurs when the amino group is protonated ($NH_3^+$) and the carboxyl group is deprotonated ($COO^-$), resulting in a molecule with both positive and negative charges.

Question 6

Which of the following biomacromolecules is NOT a polymer?

Accepted Answer

Correct Option: D. Solution: Lipids are not considered polymers because they do not consist of repeating monomeric units, unlike proteins, nucleic acids, and polysaccharides.

Question 7

Which of the following factors does NOT affect enzyme activity?

Accepted Answer

Correct Option: D. Solution: Enzyme activity is affected by temperature, pH, and substrate concentration, but not by the color of the enzyme.

Question 8

During transcription, which enzyme synthesizes RNA from a DNA template?

Accepted Answer

Correct Option: A. Solution: RNA polymerase is the enzyme that synthesizes RNA from a DNA template during transcription.

Question 9

Which of the following amino acids is considered aromatic?

Accepted Answer

Correct Option: C. Solution: Tyrosine is an aromatic amino acid due to the presence of a phenolic group in its R group.

Question 10

Which of the following amino acids is classified as an aromatic amino acid based on its R group?

Accepted Answer

Correct Option: C. Solution: Tyrosine is classified as an aromatic amino acid due to its phenolic R group, which contains a benzene ring.

Question 11

What is the primary structure of a protein?

Accepted Answer

Correct Option: A. Solution: The primary structure of a protein is the linear sequence of amino acids linked by peptide bonds.

Question 12

Which polysaccharide forms helical secondary structures and can hold iodine molecules, resulting in a blue color?

Accepted Answer

Correct Option: B. Solution: Starch forms helical structures that can trap iodine molecules, producing a characteristic blue color.

Question 13

Which of the following polysaccharides is a homopolymer consisting of glucose units?

Accepted Answer

Correct Option: A. Solution: Cellulose is a homopolymer made up of glucose units, forming long chains that provide structural support in plant cell walls.

Question 14

Which of the following is a small molecular weight biomolecule found in living tissues?

Accepted Answer

Correct Option: C. Solution: Amino acids are small molecular weight biomolecules found in living tissues, unlike polysaccharides, proteins, and DNA which are macromolecules.

Question 15

Which of the following statements best describes the role of lipids in the acid-insoluble fraction of a living tissue?

Accepted Answer

Correct Option: B. Solution: Lipids, despite their small molecular weight, are part of the acid-insoluble fraction because they are associated with membrane structures that form vesicles and are not water soluble.

Question 16

Which component of nucleic acids serves as the genetic material in cells?

Accepted Answer

Correct Option: C. Solution: Nucleotides are the building blocks of nucleic acids (DNA and RNA), which carry genetic information in cells.

Question 17

In the context of biomacromolecules, what is the primary structure of a protein?

Accepted Answer

Correct Option: A. Solution: The primary structure of a protein is defined by the linear sequence of amino acids in its polypeptide chain.

Question 18

An enzyme is observed to have its highest activity at a temperature of 37°C and a pH of 7.4. Which of the following scenarios is most likely to decrease the enzyme's activity significantly?

Accepted Answer

Correct Option: A. Solution: Increasing the temperature to 50°C can lead to denaturation of the enzyme, significantly decreasing its activity. Enzymes generally function optimally within a narrow temperature range, and high temperatures can disrupt their tertiary structure.

Question 19

Which of the following statements best describes how enzymes lower the activation energy of a reaction?

Accepted Answer

Correct Option: B. Solution: Enzymes lower the activation energy by providing an alternative pathway for the reaction, which stabilizes the transition state and reduces the energy barrier for the reaction.

Question 20

Which of the following polysaccharides is primarily used for energy storage in animal cells?

Accepted Answer

Correct Option: C. Solution: Glycogen is the polysaccharide used for energy storage in animal cells, whereas starch is used in plants.

Question 21

In a hypothetical scenario, if a cell is unable to synthesize nucleosides, which of the following processes would be directly affected?

Accepted Answer

Correct Option: B. Solution: Nucleosides are precursors to nucleotides, which are essential for DNA replication. Without nucleosides, nucleotide synthesis would be impaired, directly affecting DNA replication.

Question 22

Which of the following statements about enzymes is true?

Accepted Answer

Correct Option: C. Solution: Enzymes are proteins that catalyze biochemical reactions by lowering the activation energy required, thus increasing the rate of the reactions. They are typically sensitive to temperature and pH and may require cofactors to be active.

Question 23

In the context of small molecular weight biomolecules, which of the following statements is true?

Accepted Answer

Correct Option: B. Solution: Fatty acids are small molecular weight biomolecules, whereas nucleotides, proteins, and polysaccharides are considered macromolecules.

Question 24

Which of the following is a characteristic feature of lipids?

Accepted Answer

Correct Option: B. Solution: Lipids, including fatty acids and phospholipids, are essential for cell membrane structure and are characterized by their hydrophobic nature.

Question 25

Which of the following correctly describes the difference between a nucleoside and a nucleotide?

Accepted Answer

Correct Option: A. Solution: A nucleoside is composed of a nitrogenous base and a sugar. When a phosphate group is added to a nucleoside, it becomes a nucleotide.

Question 26

Which type of enzyme catalyzes the rearrangement of atoms within a molecule, resulting in the conversion of isomers?

Accepted Answer

Correct Option: C. Solution: Isomerases are enzymes that catalyze the rearrangement of atoms within a molecule, resulting in the conversion of one isomer to another, including optical, geometric, or positional isomers.

Question 27

A mutation in the gene coding for a protein changes one amino acid in the primary structure. Which level of protein structure is directly altered by this mutation?

Accepted Answer

Correct Option: A. Solution: The primary structure is the sequence of amino acids in a protein. A mutation that changes one amino acid directly alters this sequence.

Question 28

In the enzyme classification system, which class of enzymes is responsible for catalyzing the transfer of a functional group from one molecule to another?

Accepted Answer

Correct Option: B. Solution: Transferases are enzymes that catalyze the transfer of a functional group, such as a methyl or phosphate group, from one molecule (donor) to another (acceptor).

Question 29

Consider a protein that primarily consists of beta-pleated sheets. What type of secondary structure does this protein exhibit?

Accepted Answer

Correct Option: B. Solution: Beta-pleated sheets are a type of secondary structure characterized by sheet-like formations stabilized by hydrogen bonds.

Question 30

Which of the following statements correctly describes the role of secondary metabolites in plants?

Accepted Answer

Correct Option: C. Solution: Secondary metabolites such as alkaloids and flavonoids are not essential for basic physiological processes but have ecological roles and human uses.

Question 31

Which of the following is NOT a biomacromolecule?

Accepted Answer

Correct Option: D. Solution: Lipids are not considered biomacromolecules because their molecular weights do not exceed 800 Da, unlike proteins, nucleic acids, and polysaccharides.

Question 32

In an enzyme-catalyzed reaction, what is the role of the enzyme-substrate complex?

Accepted Answer

Correct Option: B. Solution: The enzyme-substrate complex is a temporary intermediate that facilitates the conversion of the substrate into the product by stabilizing the transition state.

Question 33

Which of the following lipids is most likely to be found in the neural tissues due to its complex structure?

Accepted Answer

Correct Option: D. Solution: Sphingomyelin is a type of sphingolipid that is abundant in the myelin sheath of nerve cells, providing insulation and facilitating rapid transmission of nerve impulses.

Question 34

What is the primary function of enzymes in biochemical reactions?

Accepted Answer

Correct Option: B. Solution: Enzymes catalyze biochemical reactions by lowering the activation energy required for the reaction to proceed.

Question 35

In a hypothetical scenario, a protein loses its quaternary structure but retains its tertiary structure. What is the most likely consequence of this change?

Accepted Answer

Correct Option: B. Solution: The quaternary structure involves the assembly of multiple polypeptide subunits. Losing this structure means the protein can no longer form multi-subunit complexes.

Question 36

Which of the following is an example of competitive inhibition in enzyme activity?

Accepted Answer

Correct Option: A. Solution: Competitive inhibition occurs when an inhibitor resembles the substrate and competes for the active site. Malonate resembles succinate and inhibits succinic dehydrogenase.

Question 37

Which of the following statements best describes the role of phospholipids in cellular structures?

Accepted Answer

Correct Option: B. Solution: Phospholipids are essential components of cell membranes because they have hydrophilic heads and hydrophobic tails, allowing them to form bilayers that separate the internal environment of the cell from the external environment.

Question 38

Which of the following is a coenzyme that participates in redox reactions and is derived from niacin?

Accepted Answer

Correct Option: B. Solution: NAD (Nicotinamide adenine dinucleotide) is a coenzyme derived from niacin and is involved in redox reactions, acting as an electron carrier.

Question 39

In the process of DNA replication, which enzyme is primarily responsible for adding nucleotides to the growing DNA strand?

Accepted Answer

Correct Option: B. Solution: DNA polymerase is the enzyme responsible for adding nucleotides to the growing DNA strand during DNA replication.

Question 40

In a peptide bond formation, which functional groups of amino acids react together?

Accepted Answer

Correct Option: B. Solution: In peptide bond formation, the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water.

Question 41

Which of the following is a nucleoside?

Accepted Answer

Correct Option: B. Solution: A nucleoside consists of a nitrogenous base attached to a sugar. Adenosine is a nucleoside composed of adenine and ribose.

Question 42

Which of the following statements best describes the role of an enzyme's active site?

Accepted Answer

Correct Option: B. Solution: The active site of an enzyme is a flexible region that changes shape to fit the substrate, allowing for the formation of the enzyme-substrate complex.

Question 43

Which of the following is a characteristic feature of proteins that allows them to perform a wide variety of functions in living organisms?

Accepted Answer

Correct Option: C. Solution: Proteins are heteropolymers made of amino acids, which allows them to have diverse structures and functions, including acting as enzymes, hormones, and antibodies.

Question 44

Which of the following statements best describes the enzyme-substrate complex?

Accepted Answer

Correct Option: B. Solution: The enzyme-substrate complex is a transient formation that facilitates the conversion of substrate into product.

Question 45

Which level of protein structure is primarily responsible for the 3D folding of a single polypeptide chain, forming a functional protein?

Accepted Answer

Correct Option: C. Solution: The tertiary structure is responsible for the 3D folding of a single polypeptide chain, forming a functional protein by arranging the secondary structures into a specific shape.

Question 46

Which level of protein structure is characterized by the formation of alpha-helices and beta-sheets?

Accepted Answer

Correct Option: B. Solution: The secondary structure of proteins involves the formation of alpha-helices and beta-pleated sheets through hydrogen bonding.

Question 47

What is the role of an enzyme in a biochemical reaction?

Accepted Answer

Correct Option: B. Solution: Enzymes lower the activation energy of reactions, making it easier for the substrate to be converted into the product.

Question 48

Which of the following proteins is the most abundant in the biosphere?

Accepted Answer

Correct Option: B. Solution: Ribulose bisphosphate Carboxylase-Oxygenase (RuBisCO) is the most abundant protein in the whole of the biosphere.

Question 49

In the context of enzyme activity, what is the effect of a competitive inhibitor?

Accepted Answer

Correct Option: C. Solution: A competitive inhibitor resembles the substrate and competes for the active site, thus decreasing enzyme activity.

Question 50

Which of the following small molecular weight biomolecules is correctly matched with its primary role in living organisms?

Accepted Answer

Correct Option: C. Solution: Sugars are small molecular weight biomolecules that provide energy through metabolic pathways and serve as structural components in cells, such as in the formation of polysaccharides.

Question 51

How does the tertiary structure of a protein differ from its secondary structure?

Accepted Answer

Correct Option: B. Solution: The tertiary structure of a protein refers to the three-dimensional folding of a single polypeptide chain, which is essential for its biological function.

Question 52

What is the primary difference between DNA and RNA?

Accepted Answer

Correct Option: A. Solution: DNA contains deoxyribose sugar, while RNA contains ribose sugar. This is a key structural difference between the two nucleic acids.

Question 53

Which of the following statements about enzymes is TRUE?

Accepted Answer

Correct Option: B. Solution: Enzymes lower the activation energy required for reactions, thus increasing the reaction rate.

Question 54

In the formation of a peptide bond, which of the following occurs?

Accepted Answer

Correct Option: A. Solution: A peptide bond is formed when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of $H_2O$.

Question 55

In a hypothetical scenario, a mutation causes a structural change in the active site of an enzyme. Which of the following outcomes is most likely?

Accepted Answer

Correct Option: C. Solution: A structural change in the active site of an enzyme can lead to a loss of substrate binding ability, thereby reducing or eliminating the enzyme's catalytic activity.

Question 56

Which type of enzyme catalyzes the conversion of a substrate by adding a water molecule, resulting in the cleavage of a bond?

Accepted Answer

Correct Option: C. Solution: Hydrolases are enzymes that catalyze the hydrolysis of various bonds, such as ester, ether, peptide, glycosidic, C-C, C-halide, or P-N bonds, by adding a water molecule.

Question 57

Which nitrogenous base is found in RNA but not in DNA?

Accepted Answer

Correct Option: B. Solution: Uracil is found in RNA instead of thymine, which is found in DNA.

Question 58

Which nitrogenous bases are found in nucleic acids?

Accepted Answer

Correct Option: A. Solution: The nitrogenous bases found in nucleic acids are adenine, guanine, cytosine, thymine (in DNA), and uracil (in RNA).

Question 59

What is the primary difference in the chemical composition of living tissues compared to the earth's crust?

Accepted Answer

Correct Option: B. Solution: The primary difference is the higher relative abundance of carbon and hydrogen in living tissues compared to the earth's crust.

Question 60

How do enzymes increase the rate of chemical reactions?

Accepted Answer

Correct Option: B. Solution: Enzymes increase the rate of chemical reactions by lowering the activation energy required, making it easier for the reaction to proceed.

Question 61

Which of the following proteins is known as the most abundant protein in the biosphere?

Accepted Answer

Correct Option: B. Solution: RuBisCO (Ribulose bisphosphate Carboxylase-Oxygenase) is considered the most abundant protein in the entire biosphere due to its role in the Calvin cycle of photosynthesis.

Question 62

In which form do animals store polysaccharides for energy?

Accepted Answer

Correct Option: C. Solution: Animals store polysaccharides in the form of glycogen, which serves as an energy reserve.

Question 63

What is the primary structural difference between starch and cellulose?

Accepted Answer

Correct Option: B. Solution: Starch forms helical structures, allowing it to hold $I_2$ molecules, whereas cellulose forms linear chains without complex helices.

Question 64

A patient is found to have a deficiency in fatty acids. Which of the following symptoms might they exhibit due to this deficiency?

Accepted Answer

Correct Option: A. Solution: Fatty acids are crucial for maintaining the integrity and fluidity of cell membranes. A deficiency can lead to weakened cell membranes, making cells more susceptible to damage and infection.

Protein	Functions
Collagen	Intercellular ground substance
Trypsin	Enzyme
Insulin	Hormone
Antibody	Fights infectious agents
Receptor	Sensory reception
GLUT-4	Enables glucose transport into cells

Biomolecules

Learning Objectives

Revision Notes & Summary

Chapter 9: Biomolecules

9.1 How to Analyse Chemical Composition?

9.2 Primary and Secondary Metabolites

Table 9.3: Some Secondary Metabolites

9.3 Biomacromolecules

9.4 Proteins

Table 9.5: Some Proteins and their Functions

9.5 Polysaccharides

9.6 Nucleic Acids

9.7 Structure of Proteins

9.8 Enzymes

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Multiple Choice Questions

Q1.How does a competitive inhibitor affect enzyme activity?

Correct Answer: B

Q2.Which of the following is a component of the acid-insoluble fraction of living tissues?

Correct Answer: B

Q3.What happens to enzyme activity when the temperature exceeds the optimum level?

Correct Answer: C

Q4.Which factor does NOT affect enzyme activity?

Correct Answer: D

Q5.Which statement correctly describes the zwitterionic form of amino acids?

Correct Answer: A

Q6.Which of the following biomacromolecules is NOT a polymer?

Correct Answer: D

Q7.Which of the following factors does NOT affect enzyme activity?

Correct Answer: D

Q8.During transcription, which enzyme synthesizes RNA from a DNA template?

Correct Answer: A

Q9.Which of the following amino acids is considered aromatic?

Correct Answer: C

Q10.Which of the following amino acids is classified as an aromatic amino acid based on its R group?

Correct Answer: C

Q11.What is the primary structure of a protein?

Correct Answer: A

Q12.Which polysaccharide forms helical secondary structures and can hold iodine molecules, resulting in a blue color?

Correct Answer: B

Q13.Which of the following polysaccharides is a homopolymer consisting of glucose units?

Correct Answer: A

Q14.Which of the following is a small molecular weight biomolecule found in living tissues?

Correct Answer: C

Q15.Which of the following statements best describes the role of lipids in the acid-insoluble fraction of a living tissue?

Correct Answer: B

Q16.Which component of nucleic acids serves as the genetic material in cells?

Correct Answer: C

Q17.In the context of biomacromolecules, what is the primary structure of a protein?

Correct Answer: A

Q18.An enzyme is observed to have its highest activity at a temperature of 37°C and a pH of 7.4. Which of the following scenarios is most likely to decrease the enzyme's activity significantly?

Correct Answer: A

Q19.Which of the following statements best describes how enzymes lower the activation energy of a reaction?

Correct Answer: B

Q20.Which of the following polysaccharides is primarily used for energy storage in animal cells?

Correct Answer: C

Q21.In a hypothetical scenario, if a cell is unable to synthesize nucleosides, which of the following processes would be directly affected?

Correct Answer: B

Q22.Which of the following statements about enzymes is true?

Correct Answer: C

Q23.In the context of small molecular weight biomolecules, which of the following statements is true?

Correct Answer: B

Q24.Which of the following is a characteristic feature of lipids?

Correct Answer: B

Q25.Which of the following correctly describes the difference between a nucleoside and a nucleotide?

Correct Answer: A

Q26.Which type of enzyme catalyzes the rearrangement of atoms within a molecule, resulting in the conversion of isomers?

Correct Answer: C

Q27.A mutation in the gene coding for a protein changes one amino acid in the primary structure. Which level of protein structure is directly altered by this mutation?

Correct Answer: A