On a single process of the Krebs Cycle, decarboxylation takes place in ___ steps.

Options

A. Five
B. Four
C. Three
D. Two

Answer

To solve the question regarding the number of steps in the Krebs Cycle where decarboxylation occurs, we can follow these steps:

### Step 1: Understand the Krebs Cycle
The Krebs Cycle, also known as the Citric Acid Cycle or TCA Cycle, is a series of biochemical reactions that take place in the mitochondria of eukaryotic cells. It is crucial for energy production through the oxidation of acetyl coenzyme A.

**Hint:** Familiarize yourself with the Krebs Cycle and its overall purpose in cellular respiration.

### Step 2: Identify Decarboxylation
Decarboxylation is a chemical reaction that involves the removal of a carboxyl group (-COOH) from a molecule, releasing carbon dioxide (CO2). In the context of the Krebs Cycle, we need to identify where this process occurs.

**Hint:** Look for the specific reactions in the Krebs Cycle that involve the conversion of a carbon compound into a compound with fewer carbon atoms, indicating decarboxylation.

### Step 3: Locate the Steps of Decarboxylation
In the Krebs Cycle, decarboxylation occurs specifically in two steps:
1. **Step 4:** Isocitrate (6-carbon compound) is converted into alpha-ketoglutarate (5-carbon compound) with the release of CO2.
2. **Step 5:** Alpha-ketoglutarate (5-carbon compound) is converted into succinyl coenzyme A (4-carbon compound), also releasing CO2.

**Hint:** Remember the specific enzymes involved in these reactions: isocitrate dehydrogenase for the first decarboxylation and alpha-ketoglutarate dehydrogenase for the second.

### Step 4: Conclusion
Based on the above analysis, we conclude that decarboxylation takes place in **two steps** during a single process of the Krebs Cycle.

**Final Answer:** The number of steps in the Krebs Cycle where decarboxylation occurs is **two**.