How many TCA cyles are required during the complete oxidation of one sucrose molecule ?

Options

A. 4
B. 2
C. 1
D. 3

Answer

To determine how many TCA cycles are required for the complete oxidation of one sucrose molecule, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Composition of Sucrose**:
- Sucrose is a disaccharide composed of two monosaccharides: glucose and fructose.

2. **Oxidation of Glucose**:
- During cellular respiration, one molecule of glucose undergoes glycolysis to produce two molecules of pyruvate.
- Each pyruvate is then converted into one molecule of acetyl-CoA through a process called decarboxylation.
- Therefore, from one glucose molecule, we get **2 acetyl-CoA**.

3. **TCA Cycle Entry**:
- Each acetyl-CoA enters the TCA cycle once. Thus, from one glucose molecule, **2 TCA cycles** are run.

4. **Oxidation of Fructose**:
- Fructose also enters glycolysis, where it is converted into fructose-6-phosphate, which can then be metabolized similarly to glucose.
- Like glucose, one molecule of fructose will also yield **2 acetyl-CoA** after glycolysis and subsequent decarboxylation.

5. **Total TCA Cycles for Sucrose**:
- Since sucrose yields 2 acetyl-CoA from glucose and 2 acetyl-CoA from fructose, the total number of acetyl-CoA produced from one sucrose molecule is **4**.
- Consequently, this means that **4 TCA cycles** are required for the complete oxidation of one sucrose molecule.

6. **Final Answer**:
- The correct answer is **4 TCA cycles**.

### Summary:
For the complete oxidation of one sucrose molecule, **4 TCA cycles** are required.

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