During electron transport system (ETS) electron transport proceeds from carriers that have ________redox potential to those having_____redox potential. This electront transport down the energy gradient leads to the formation of ATP from ADP and Pi, which is referred to as___________.

Options

A. low, high, oxidative phosphorylation
B. low, high, oxidative decarboxylation
C. high, low, oxidative phosphorylation
D. high, low, oxidative decarboxylation

Explanation

### Step-by-Step Solution:

1. **Understanding the Electron Transport System (ETS)**:
- The electron transport system is a series of protein complexes and other molecules that transfer electrons from electron donors (like NADH and FADH2) to electron acceptors (like oxygen).

2. **Redox Potential Concept**:
- Redox potential refers to the tendency of a chemical species to acquire electrons and thereby be reduced. In the context of ETS, carriers with low redox potential donate electrons to carriers with high redox potential.

3. **Direction of Electron Transport**:
- Electrons move from carriers with lower redox potential to those with higher redox potential. This movement is crucial as it allows for the release of energy, which is harnessed to form ATP.

4. **Formation of ATP**:
- The energy released during the electron transport down the energy gradient is used to convert ADP and inorganic phosphate (Pi) into ATP. This process is known as oxidative phosphorylation.

5. **Choosing the Correct Options**:
- Based on the understanding of the electron transport system:
- The first blank should be filled with "low" (indicating low redox potential).
- The second blank should be filled with "high" (indicating high redox potential).
- The final blank should be filled with "oxidative phosphorylation" (the process of ATP formation).

6. **Final Answer**:
- Therefore, the complete answer is: During electron transport system (ETS), electron transport proceeds from carriers that have **low** redox potential to those having **high** redox potential. This electron transport down the energy gradient leads to the formation of ATP from ADP and Pi, which is referred to as **oxidative phosphorylation**.