GATE BT 2024 • Q25
MCQ • 1 Mark
Section 2: General Biotechnology
Bioenergetics and Metabolism
Subtopic: Thermodynamics & ATP Bioenergetics
Question Statement:
Krebs (TCA) cycle is ________ pathway.
Options:
-
(A) only an anabolic
-
(B) only a catabolic
-
(C) an amphibolic
-
(D) a pyogenic
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2024 Q.25)**
**1. Governing Concept**:
- **Topic**: Cellular Respiration & Intermediary Metabolism
- The Krebs (Citric Acid / Tricarboxylic Acid) cycle serves dual biological functions:
- **Catabolic function**: Oxidizes acetyl-CoA derived from carbohydrates, fats, and amino acids to $\text{CO}_2$, yielding reducing equivalents ($\text{NADH}, \text{FADH}_2$) and $\text{GTP}/\text{ATP}$.
- **Anabolic function**: Cycle intermediates serve as biosynthetic precursors for gluconeogenesis (oxaloacetate), amino acid synthesis ($\alpha$-ketoglutarate, oxaloacetate), and heme synthesis (succinyl-CoA).
- A pathway possessing both catabolic and anabolic roles is termed **amphibolic**.
**2. Option Analysis**:
- **Option (A) [only an anabolic] is INCORRECT**: Ignores its primary role in catabolic terminal oxidation.
- **Option (B) [only a catabolic] is INCORRECT**: Ignores cataplerotic biosynthetic precursor generation.
- **Option (C) [an amphibolic] is CORRECT**: Fully captures both catabolic energy harvesting and anabolic precursor provision.
- **Option (D) [a pyogenic] is INCORRECT**: Pyogenic means pus-inducing, completely irrelevant to biochemical pathways.
**3. Final Answer**:
- **Correct Choice**: **C**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.
Launch CBT Mock Test