Which of the following statements regarding co-factors, prosthetic groups, and co-enzymes are correct?
Statement I: Co-factors are non-protein components required for the catalytic activity of enzymes, where the protein portion is called the apoenzyme. Statement II: Prosthetic groups are organic compounds that are tightly and permanently bound to the apoenzyme (e.g., haem in catalase). Statement III: Co-enzymes are organic compounds whose association with the apoenzyme is transient during catalysis (e.g., NAD containing Niacin). Statement IV: Removing a co-factor from an enzyme increases its catalytic rate by 100-fold.
Statement IV is incorrect because removing a co-factor causes catalytic activity to be completely lost. Statements I, II, and III faithfully state co-factor definitions.
Question 82 of 100
📘 CLASS XI
Which of the following statements regarding polysaccharide structures and the iodine test are correct?
Statement I: Starch forms helical secondary structures that trap iodine (I₂) molecules, turning blue. Statement II: Cellulose lacks complex helices and cannot hold iodine. Statement III: Glycogen is a branched storage polysaccharide in animals with a reducing right end and non-reducing left end. Statement IV: Inulin is a polymer of glucose monosaccharides linked by peptide bonds.
Statement IV is incorrect because inulin is a polymer of fructose monosaccharides linked by glycosidic bonds. Statements I, II, and III correctly describe helical iodine binding and glycogen polarity.
Question 83 of 100
📘 CLASS XI
Which of the following statements regarding cellular mass percentage composition (NCERT Table 9.4) are correct?
Statement I: Water is the most abundant chemical in living cells (70–90% of total mass). Statement II: Proteins are the most abundant organic macromolecules in cells (10–15% of total mass). Statement III: Nucleic acids constitute 5–7% of total cellular mass. Statement IV: Lipids constitute 20% of total cellular mass, while carbohydrates make up only 0.1%.
Statement IV is incorrect because lipids constitute 2% and carbohydrates constitute 3% of total cellular mass according to NCERT Table 9.4. Statements I, II, and III are accurate.
Question 84 of 100
📘 CLASS XI
Which of the following statements regarding zwitterionic chemistry of amino acids are correct?
Statement I: Amino acids are substituted methanes possessing an amino group, carboxyl group, hydrogen, and variable R-group on the α-carbon. Statement II: Glycine has hydrogen as its R-group, alanine has a methyl group, and serine has a hydroxy methyl group. Statement III: In zwitterionic form, an amino acid carries both positive (-NH₃⁺) and negative (-COO⁻) charges. Statement IV: In strongly alkaline pH, amino acids exist primarily in a protonated cationic form.
Statement IV is incorrect because in strongly alkaline pH, amino acids exist predominantly in an anionic (negatively charged) form. Statements I, II, and III accurately specify substituted methane structure and zwitterions.
Question 85 of 100
📘 CLASS XI
Which of the following statements regarding fatty acids, glycerides, and oils are correct?
Statement I: Palmitic acid contains 16 carbon atoms including the carboxyl carbon. Statement II: Arachidonic acid contains 20 carbon atoms including the carboxyl carbon. Statement III: Glycerol is trihydroxy propane. Statement IV: Fats have lower melting points than oils and remain liquid during winter.
Statement IV is inverted and incorrect because oils have lower melting points and remain liquid during winter, whereas fats have higher melting points. Statements I, II, and III accurately state fatty acid carbon numbers and glycerol chemistry.
Question 86 of 100
📘 CLASS XI
Which of the following statements regarding secondary metabolite categories (NCERT Table 9.3) are correct?
Statement I: Carotenoids and anthocyanins are pigments. Statement II: Monoterpenes and diterpenes are terpenoids. Statement III: Vinblastin and curcumin are drugs. Statement IV: Rubber, gums, and cellulose are alkaloids.
Statement IV is incorrect because rubber, gums, and cellulose are classified as polymeric substances, whereas morphine and codeine are alkaloids. Statements I, II, and III strictly match NCERT Table 9.3.
Question 87 of 100
📘 CLASS XI
Which of the following statements regarding nitrogenous bases, nucleosides, and nucleotides are correct?
Statement I: Adenine and Guanine are purines, while Cytosine, Uracil, and Thymine are pyrimidines. Statement II: Adenosine, Guanosine, Cytidine, Uridine, and Thymidine are nucleosides. Statement III: Adenylic acid, Guanylic acid, Cytidylic acid, Uridylic acid, and Thymidylic acid are nucleotides. Statement IV: Phosphate group attached to a pentose sugar via an ester linkage forms a nucleoside.
Statement IV is incorrect because esterification of phosphate to a pentose sugar forms a nucleotide, whereas a nucleoside lacks a phosphate group. Statements I, II, and III correctly distinguish purines, pyrimidines, nucleosides, and nucleotides.
Question 88 of 100
📘 CLASS XI
Which of the following statements regarding the mechanism of enzyme catalysis and energy barriers are correct?
Statement I: Enzymes lower the activation energy barrier to accelerate the conversion of substrate S to product P. Statement II: Substrate binding induces a conformational change in the enzyme to fit tightly around the substrate. Statement III: Transient intermediate states between substrate and product are unstable. Statement IV: Enzymes shift the equilibrium constant (Keq) 100-fold toward products in exothermic reactions.
Statement IV is incorrect because enzymes do not alter the equilibrium constant (Keq); they only accelerate the rate at which equilibrium is attained. Statements I, II, and III faithfully state transition state principles.
Question 89 of 100
📘 CLASS XI
Which of the following statements regarding factors affecting enzyme activity and saturation kinetics are correct?
Statement I: Enzyme activity curves against temperature and pH show a bell-shaped profile with a distinct optimum point. Statement II: Low temperature preserves enzymes in a temporarily inactive state. Statement III: High temperature causes irreversible thermal denaturation of proteins. Statement IV: Reaction velocity (V) increases endlessly beyond Vmax upon adding excess substrate.
Statement IV is incorrect because once enzyme active sites are saturated, velocity reaches a plateau at Vmax and cannot be increased further by adding substrate. Statements I, II, and III accurately describe enzyme kinetics.
Question 90 of 100
📘 CLASS XI
Which of the following statements regarding competitive inhibition and pathogen control are correct?
Statement I: Competitive inhibitors are structural analogs that compete with the substrate for active site binding. Statement II: Malonate inhibits succinic dehydrogenase by competing with succinate. Statement III: Competitive inhibitors are used in controlling bacterial pathogens. Statement IV: Competitive inhibition can be reversed by adding more inhibitor molecules to the medium.
Statement IV is incorrect because competitive inhibition is reversed by increasing substrate concentration, not inhibitor concentration. Statements I, II, and III accurately state competitive inhibition principles.
