How many ATP molecules are released when one molecules of glucose is oxidised in our liver cells ?

Options

A. 36
B. 38
C. 2
D. 8

Answer

To determine how many ATP molecules are released when one molecule of glucose is oxidized in liver cells, we will follow the process of aerobic respiration step by step.

### Step-by-Step Solution:

1. **Glycolysis**:
- In the cytoplasm, one molecule of glucose is converted into two molecules of pyruvate.
- During this process, **2 ATP** molecules are produced directly.
- Additionally, **2 NADH** molecules are formed, which will contribute to ATP production later.

2. **Link Reaction**:
- Each pyruvate is converted into acetyl CoA, and during this conversion, **2 NADH** molecules are produced (1 NADH per pyruvate, and since there are 2 pyruvates, we have 2 NADH).
- No ATP is produced during this step.

3. **Krebs Cycle (Citric Acid Cycle)**:
- Each acetyl CoA enters the Krebs cycle. Since there are 2 acetyl CoA molecules (from the original glucose), the cycle turns twice.
- In each turn of the cycle, **1 ATP** is produced. Therefore, for 2 turns, **2 ATP** are produced.
- Additionally, **6 NADH** and **2 FADH2** are produced (3 NADH and 1 FADH2 per turn).

4. **Total ATP from Glycolysis, Link Reaction, and Krebs Cycle**:
- From Glycolysis: **2 ATP** + **2 NADH**
- From Link Reaction: **2 NADH**
- From Krebs Cycle: **2 ATP** + **6 NADH** + **2 FADH2**
- Total ATP from direct production: **2 ATP (Glycolysis) + 2 ATP (Krebs Cycle) = 4 ATP**
- Total NADH: **2 (Glycolysis) + 2 (Link Reaction) + 6 (Krebs Cycle) = 10 NADH**
- Total FADH2: **2 FADH2 (Krebs Cycle)**

5. **Electron Transport Chain**:
- Each NADH can produce approximately **3 ATP** when oxidized in the electron transport chain, and each FADH2 can produce approximately **2 ATP**.
- From **10 NADH**: 10 NADH x 3 ATP/NADH = **30 ATP**
- From **2 FADH2**: 2 FADH2 x 2 ATP/FADH2 = **4 ATP**

6. **Total ATP Calculation**:
- Total ATP from substrate-level phosphorylation: **4 ATP**
- Total ATP from oxidative phosphorylation: **30 ATP (from NADH) + 4 ATP (from FADH2) = 34 ATP**
- Adding these together gives us: **4 ATP + 34 ATP = 38 ATP**

### Final Answer:
When one molecule of glucose is oxidized in liver cells, a total of **38 ATP molecules** are produced.

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