In eukaryotes complete oxidation of a glucose molecule results in the net gain of how many ATP molecules?

Options

A. 2
B. 4
C. 36
D. 38

Explanation

To determine the net gain of ATP molecules from the complete oxidation of a glucose molecule in eukaryotes, we can break down the process into three main stages:

### Step 1: Glycolysis
- **Process**: Glycolysis is the first step in the breakdown of glucose, which occurs in the cytoplasm. During this process, one glucose molecule (6 carbon atoms) is converted into two molecules of pyruvic acid (3 carbon atoms each).
- **ATP Yield**: In glycolysis, a net gain of **2 ATP** molecules is produced directly. However, if we consider the total ATP produced (including those used), it can be counted as **4 ATP** produced, but since 2 ATP are consumed in the process, the net gain is **2 ATP**.

### Step 2: Oxidative Decarboxylation
- **Process**: The pyruvic acid produced in glycolysis is then transported into the mitochondria, where it undergoes oxidative decarboxylation to form acetyl-CoA. This step also releases carbon dioxide.
- **ATP Yield**: During this process, **2 NADH** are produced, which can be converted to **6 ATP** (since each NADH can produce approximately 3 ATP in the electron transport chain).

### Step 3: TCA Cycle (Krebs Cycle)
- **Process**: The acetyl-CoA enters the TCA cycle, where it is further oxidized, leading to the production of carbon dioxide and high-energy electron carriers.
- **ATP Yield**: In one turn of the TCA cycle, **3 NADH**, **1 FADH2**, and **1 ATP (or GTP)** are produced. Since each NADH yields about 3 ATP and each FADH2 yields about 2 ATP, for two turns (since one glucose molecule produces two acetyl-CoA), we get:
- From NADH: 6 NADH x 3 ATP = 18 ATP
- From FADH2: 2 FADH2 x 2 ATP = 4 ATP
- From ATP (or GTP): 2 ATP
- **Total from TCA Cycle**: 18 ATP + 4 ATP + 2 ATP = **24 ATP**.

### Final Calculation
Now, we can sum up all the ATP produced from each step:
- Glycolysis: **2 ATP** (net gain)
- Oxidative Decarboxylation: **6 ATP** (from 2 NADH)
- TCA Cycle: **24 ATP**

**Total ATP Yield**: 2 + 6 + 24 = **32 ATP**.

### Conclusion
The complete oxidation of one glucose molecule in eukaryotes results in a net gain of **approximately 30-32 ATP molecules** (considering the efficiency of the electron transport chain).