The enzyme which catalyzes geometric or structural changes within a molecule is?

DSSSB - 29 August 2019 (Shift-2)

Biochemistry & Nutrition

Easy

Appeared in: DSSSB - 29 August 2019 (Shift-2)

Explanation

Isomerases are enzymes that catalyze the conversion of a molecule into one of its isomers.
This involves rearranging the existing atoms within the molecule to change its geometric or structural configuration.
Examples include converting a cis-isomer to a trans-isomer or an L-amino acid to a D-amino acid.
The question's description of catalyzing 'geometric or structural changes within a molecule' is the precise definition of an isomerase's function.

Option B: Hydrolases break down complex molecules into simpler ones by adding water to break a chemical bond (hydrolysis). They do not simply rearrange the structure of a single molecule.
Option C: Ligases do the opposite of breaking down molecules; they join two separate molecules together to form a larger one. This process usually requires energy, often supplied by ATP.
Option D: Lyases break various chemical bonds by means other than hydrolysis and oxidation, often resulting in the formation of a new double bond or a ring structure. This involves removing a group from the molecule, not just rearranging it.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification and function of enzymes as background academic context rather than a clinical decision trigger.
Understanding enzyme classes is fundamental to biochemistry and pharmacology. Many diseases are caused by enzyme deficiencies, and many drugs work by inhibiting specific enzymes.
For example, a deficiency in the isomerase enzyme 'triosephosphate isomerase' leads to a rare but severe metabolic disorder affecting glycolysis, causing hemolytic anemia and progressive neurological dysfunction.
What if a patient has a genetic defect in a ligase enzyme? This could lead to conditions like 'DNA ligase I deficiency', characterized by immunodeficiency, growth retardation, and sun sensitivity, because the cell's ability to repair DNA is compromised.

How to Approach the Question

First, identify the key action described in the question stem: 'catalyzes geometric or structural changes within a molecule'.
Break down this phrase: 'within a molecule' implies an intramolecular reaction, and 'geometric or structural changes' points to rearrangement.
Recall the six major classes of enzymes and their primary functions.
Match the action from the stem to the definition of each enzyme class.
Isomerases are defined as enzymes that rearrange atoms within a molecule to create isomers. This is a perfect match.
Eliminate the other options by confirming their functions are different: Hydrolases break bonds with water, Ligases join molecules, and Lyases break bonds without water.

Concept Tested & Keywords

Concept Tested: Classification and function of enzymes
Stem keywords: enzyme, catalyzes, geometric changes, structural changes, molecule
Lead-in keywords: is

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 44-46

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 44-46