Q.21 Find the odd one among the following:
- James Sumner → Urease
- Holoenzyme → Functional enzyme plus coenzyme and/or metal ion
- Apoenzyme → Enzyme + prosthetic group
- Hexokinase → Mg2+ dependent
James Sumner → Urease is the odd one out, as it represents a historical scientist-enzyme association rather than a biochemical definition of enzyme components or properties.
Option Analysis
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James Sumner → Urease. Correct odd one. James Sumner crystallized urease from jack beans in 1926, proving enzymes are proteins (Nobel Prize 1946), but this links a person to their discovery, unlike the other definitional statements.
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Holoenzyme → Functional enzyme plus coenzyme and/or metal ion. Accurate. Holoenzyme is the complete, active enzyme comprising apoenzyme + cofactors (coenzymes like NAD⁺ or metal ions like Mg²⁺), distinguishing it from inactive forms.
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Apoenzyme → Enzyme + prosthetic group. Accurate. Apoenzyme is the protein (inactive) portion; adding a prosthetic group (tightly bound cofactor, e.g., heme) forms the functional unit, though phrasing implies the complete form.
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Hexokinase → Mg²⁺ dependent. Accurate. Hexokinase phosphorylates glucose using ATP, requiring Mg²⁺ to neutralize ATP’s phosphates for kinase activity, a classic metal-dependent enzyme example.
Introduction to Odd One in Enzymes
The odd one among James Sumner → Urease, holoenzyme, apoenzyme, and hexokinase Mg²⁺ dependent is James Sumner → Urease, as it denotes historical discovery while others define enzyme structure/function. Crucial for GATE Life Sciences exam prep on enzymology basics.
Why James Sumner-Urease Stands Out
Sumner crystallized urease, first proving enzymes’ protein nature, but it’s biographical. Holoenzyme (apo + cofactors), apoenzyme (protein sans prosthetic group), and hexokinase (Mg²⁺ for ATP binding) are mechanistic definitions.
Option Type Description James Sumner → Urease Historical link Crystallization proved enzymes = proteins Holoenzyme Definition Apoenzyme + coenzyme/metal = active form Apoenzyme Definition Protein part + prosthetic group Hexokinase Property Mg²⁺ cofactor dependent kinase Exam Tips for Enzyme Concepts
Questions test distinctions: history vs. components (holo/apo) vs. dependencies (metals). Urease requires Ni²⁺, but hexokinase exemplifies Mg²⁺ in glycolysis.
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