What is the total gain of energy during glycosis?

Options

A. One molecule of ATP
B. Two molecule of ATP
C. Four molecule of ATP
D. Eight molecule of ATP

Answer

To determine the total gain of energy during glycolysis, we can break the process down step by step:

### Step 1: Understanding Glycolysis
Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing energy in the form of ATP and NADH. It occurs in the cytoplasm and does not require oxygen (anaerobic).

**Hint:** Remember that glycolysis is the first step in both aerobic and anaerobic respiration.

### Step 2: ATP Investment Phase
In the initial phase of glycolysis, two ATP molecules are consumed to convert glucose into fructose 1,6-bisphosphate. The steps include:
- Glucose to glucose 6-phosphate (1 ATP used)
- Glucose 6-phosphate to fructose 6-phosphate (no ATP used)
- Fructose 6-phosphate to fructose 1,6-bisphosphate (1 ATP used)

**Total ATP used:** 2 ATP

**Hint:** Focus on the preparatory phase where ATP is invested to activate glucose.

### Step 3: Energy Harvesting Phase
In the subsequent phase, energy is produced:
1. The fructose 1,6-bisphosphate splits into two triose phosphates (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate).
2. Each triose phosphate is converted to pyruvate, yielding:
- 2 NADH (1 from each triose phosphate, equivalent to 3 ATP each in oxidative phosphorylation)
- 4 ATP (2 ATP from each triose phosphate during conversion to pyruvate)

**Total ATP produced:** 4 ATP (net gain of 2 ATP after subtracting the 2 ATP used) + 2 NADH (which can yield 6 ATP)

**Hint:** Remember that NADH contributes to the total ATP yield when considering oxidative phosphorylation.

### Step 4: Total Energy Gain Calculation
Now, let's summarize:
- **ATP produced:** 4 ATP (2 net gain after accounting for the 2 used)
- **NADH produced:** 2 NADH (which can yield 6 ATP in the electron transport chain)

**Total ATP equivalent from NADH:** 6 ATP

### Final Calculation
- Total ATP from glycolysis = 2 (net gain) + 6 (from NADH) = 8 ATP

### Conclusion
The total gain of energy during glycolysis, considering both the direct ATP produced and the ATP equivalent from NADH, is **8 ATP**.

**Final Answer:** The total gain of energy during glycolysis is 8 ATP.

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