5 public questions tagged with this topic.
Iron is a necessary cofactor for catalase, an enzyme that breaks down hydrogen peroxide.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Enzymes - Properties Classification and Cofactors
DNA synthesis proceeds via nucleophilic attack of primer 3' hydroxyl on alpha-phosphate of incoming dNTP. Two Mg2+ ions, coordinated by conserved aspartate residues in polymerase active site, orchestrate catalysis. One ion activates 3'OH lowering pKa for attack, the other stabilizes pentacovalent transition state and facilitates pyrophosphate departure. Without Mg2+, phosphodiester bond formation stalls entirely. This two-metal mechanism explains why chelators like EDTA inhibit polymerization, why Ca2+ fails to substitute effectively, and why high fidelity polymerases absolutely require magnesium for both polymerase and exonuclease activities.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: DNA Replication Mechanisms, Two-metal-ion catalysis
Divalent magnesium ions serve as an essential cofactor for DNA polymerases in PCR. Mg2+ coordinates with phosphate oxygens of dNTPs at the active site, facilitates nucleophilic attack by 3' hydroxyl, stabilizes negative charges during phosphodiester bond formation, and influences primer-template duplex stability. Concentration critically affects enzyme activity, fidelity, specificity, and primer annealing. Unlike an enzyme that catalyzes reaction itself, buffer that maintains pH, or template that encodes sequence, Mg2+ is a non-protein chemical activator indispensable for catalytic function and typically used at 1.5-2.5 mM.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Vitamin is the accurate answer because it correctly identifies the biological function or role described in this question. In Atoms and Molecules, understanding the specific functions of molecules, enzymes, or structures is fundamental. Vitamin fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Nucleic acid, Lipid, and Carbohydrate) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.
Ref: Campbell Biology, Urry et al., 12th Ed.
Tetrahydrofolate is the accurate answer because it correctly identifies the biological function or role described in this question. In Enzymes Basics, understanding the specific functions of molecules, enzymes, or structures is fundamental. Tetrahydrofolate fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Thiamine pyrophosphate, Lipoate, and Biocytin) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6
