Question:
In the Krebs cycle and the urea cycle, the linking amino acid is which of the following?
In the Krebs cycle and the urea cycle, the linking amino acid is which of the following?
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Its keto acid partner is oxaloacetate, a TCA intermediate.
Updated On: Jun 23, 2026
- Fumarate
- Alanine
- Arginine
- Aspartate
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The Correct Option is D
Solution and Explanation
Step 1: In the urea cycle, aspartate condenses with citrulline to form argininosuccinic acid.
Step 2: Argininosuccinic acid is then cleaved to yield arginine and fumarate, releasing fumarate back toward the mitochondrial pool.
Step 3: The keto acid counterpart of aspartate is oxaloacetate, which is a core intermediate of the TCA (Krebs) cycle. Aspartate and oxaloacetate are interconverted by transamination.
Step 4: Because aspartate feeds the urea cycle directly and connects to the Krebs cycle through oxaloacetate, it is the amino acid that links the two cycles.
Step 2: Argininosuccinic acid is then cleaved to yield arginine and fumarate, releasing fumarate back toward the mitochondrial pool.
Step 3: The keto acid counterpart of aspartate is oxaloacetate, which is a core intermediate of the TCA (Krebs) cycle. Aspartate and oxaloacetate are interconverted by transamination.
Step 4: Because aspartate feeds the urea cycle directly and connects to the Krebs cycle through oxaloacetate, it is the amino acid that links the two cycles.
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