Which of the following statements regarding primary and secondary protein structures are correct?
I. Primary structure of a protein describes the positional information and linear sequence of amino acids. II. The N-terminal amino acid is the first amino acid represented on the left end, while the C-terminal is on the right end. III. In proteins, only right-handed helices are observed in secondary structure. IV. Secondary structure includes regions folded into α-helix and β-pleated sheets.
Which of the above statements are correct?
All four statements are correct according to NCERT. Primary structure defines amino acid sequence, the chain is represented from N-terminal to C-terminal, and secondary structure includes right-handed α-helices and β-pleated sheets.
Question 42 of 100
📘 CLASS XI
Which of the following statements regarding tertiary and quaternary protein architecture are correct?
I. Tertiary structure involves a long protein chain folding upon itself like a hollow woolen ball. II. Tertiary structure provides a three-dimensional view and is absolutely necessary for the biological activities of proteins. III. Quaternary structure represents the spatial arrangement of multiple polypeptide subunits relative to each other. IV. Adult human haemoglobin consists of four identical α-type polypeptide chains.
Which of the above statements are correct?
Statement IV is incorrect because adult human haemoglobin consists of two α-type and two β-type polypeptide subunits. Statements I, II, and III correctly describe tertiary and quaternary protein structure.
Question 43 of 100
📘 CLASS XI
Which of the following statements regarding nucleic acid macromolecules and nucleotide components are correct?
I. Nucleic acids (DNA and RNA) are polynucleotides found in the acid-insoluble macromolecular fraction. II. A nucleotide consists of a heterocyclic nitrogen base, a monosaccharide pentose sugar, and phosphoric acid. III. RNA contains 2'-deoxyribose sugar while DNA contains ribose sugar. IV. Adenine and Guanine are purines with skeletal double rings, while Cytosine, Uracil, and Thymine are pyrimidines.
Which of the above statements are correct?
Statement III is incorrect because RNA contains ribose sugar, whereas DNA contains 2'-deoxyribose sugar. Statements I, II, and IV correctly describe nucleic acids, nucleotides, and nitrogenous base classification.
Question 44 of 100
📘 CLASS XI
Which of the following statements comparing inorganic catalysts and biological enzymes are correct?
I. Inorganic catalysts work efficiently at high temperatures and high pressures. II. Most enzymes get damaged and denatured at temperatures above 40°C. III. Thermophilic organisms isolated from hot vents and sulfur springs possess enzymes stable up to 80°–90°C. IV. Thermal stability is a quality of thermophilic enzymes achieved because they lack tertiary structure.
Which of the above statements are correct?
Statement IV is incorrect because enzymes require tertiary structure to create active site pockets for catalysis. Thermophilic enzymes retain their tertiary structure even at high temperatures. Statements I, II, and III correctly compare inorganic catalysts and biological enzymes.
Question 45 of 100
📘 CLASS XI
Which of the following statements regarding chemical reaction kinetics and carbonic anhydrase speed are correct?
I. Rate of a physical or chemical process is expressed as δP / δt. II. A general rule of thumb is that reaction rate doubles or decreases by half for every 10°C change in temperature in either direction. III. Uncatalysed formation of carbonic acid (H₂CO₃) produces about 200 molecules per hour. IV. Carbonic anhydrase accelerates reaction rate by 10 million times to produce 600,000 molecules per minute.
Which of the above statements are correct?
Statement IV is incorrect because carbonic anhydrase produces about 600,000 molecules every second, not every minute. Statements I, II, and III correctly describe reaction kinetics and uncatalysed reaction rates.
Question 46 of 100
📘 CLASS XI
Which of the following statements regarding activation energy profiles and transition states are correct?
I. Substrate 'S' binds to the active site of an enzyme to form a transient enzyme-substrate (ES) complex. II. During catalysis, substrate structure is transformed into a high-energy, unstable transition state structure. III. If product 'P' is at a lower potential energy level than substrate 'S', the reaction is endothermic. IV. Activation energy is the difference in average energy content of 'S' from that of the transition state.
Which of the above statements are correct?
Statement III is incorrect because if product P is at a lower potential energy level than substrate S, the reaction is exothermic. Statements I, II, and IV correctly explain ES complex formation, transition state, and activation energy.
Question 47 of 100
📘 CLASS XI
Which of the following statements regarding the steps in the catalytic cycle of enzyme action are correct?
I. The substrate first binds to the active site of the enzyme, fitting into the cleft. II. Substrate binding induces the enzyme to alter its shape, fitting more tightly around the substrate. III. The active site breaks or forms chemical bonds, generating an enzyme-product (EP) complex. IV. Upon product release, the enzyme is degraded and must be resynthesized for the next cycle.
Which of the above statements are correct?
Statement IV is incorrect because the enzyme is released unchanged after product formation and is available for another catalytic cycle. Statements I, II, and III correctly describe the catalytic cycle.
Question 48 of 100
📘 CLASS XI
Which of the following statements regarding factors affecting enzyme activity and Vmax saturation are correct?
I. Each enzyme shows maximal catalytic activity at an optimum pH and optimum temperature. II. Low temperature preserves enzymes in a temporarily inactive state, whereas high temperature denatures proteins. III. Increasing substrate concentration causes velocity to rise until it reaches maximum velocity (Vmax). IV. After enzyme saturation, adding more substrate further increases velocity indefinitely beyond Vmax.
Which of the above statements are correct?
Statement IV is incorrect because once all enzyme active sites are saturated, reaction velocity cannot exceed Vmax regardless of further substrate addition. Statements I, II, and III correctly describe enzyme kinetics.
Question 49 of 100
📘 CLASS XI
Which of the following statements regarding competitive inhibition and the succinic dehydrogenase mechanism are correct?
I. A competitive inhibitor closely resembles the substrate in molecular structure and competes for active site binding. II. Inhibition of succinic dehydrogenase by malonate (which closely resembles succinate) is a classic example of competitive inhibition. III. Competitive inhibitors are frequently used in the control of bacterial pathogens. IV. Competitive inhibitors permanently alter the primary structure of enzymes to increase Vmax.
Which of the above statements are correct?
Statement IV is incorrect because competitive inhibitors compete for the active site without altering the primary structure of enzymes or increasing Vmax. Statements I, II, and III correctly describe competitive inhibition.
Question 50 of 100
📘 CLASS XI
Which of the following statements regarding enzyme classification classes and subclasses (NCERT Section 9.8.5) are correct?
I. Enzymes are classified into 6 classes, each with 4–13 subclasses, designated by a four-digit number. II. Transferases catalyze group transfer G (other than hydrogen) between a pair of substrates S and S'. III. Lyases catalyze hydrolysis of ester, ether, peptide, and glycosidic bonds. IV. Ligases catalyze the linking together of two compounds by joining C-O, C-S, C-N, or P-O bonds.
Which of the above statements are correct?
Statement III is incorrect because Hydrolases catalyze hydrolysis of ester, ether, peptide, glycosidic and related bonds, whereas Lyases remove groups without hydrolysis, generally forming double bonds. Statements I, II, and IV correctly summarize enzyme classification.
