ATP is considered a high-energy compound because under cellular conditions, 7.3 kcal per mole of energy is released when a bond is broken between the :

Options

A. base adenine and the sugar ribose
B. adenosine and the phosphate groups
C. base adenine and the phosphate groups
D. adenosine diphosphate and the third phosphate

Explanation

To solve the question regarding why ATP is considered a high-energy compound, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding ATP Structure**:
- ATP (Adenosine Triphosphate) consists of three phosphate groups (phosphates) attached to an adenosine molecule. The bonds between these phosphate groups are known as high-energy bonds.

2. **Energy Release upon Bond Breaking**:
- When ATP is utilized for energy, it undergoes hydrolysis, where the terminal phosphate group is cleaved off. This process releases energy.

3. **Quantifying the Energy Released**:
- Under cellular conditions, the hydrolysis of ATP releases approximately 7.3 kilocalories per mole of energy. This energy is released when the bond between the last two phosphate groups (the pyrophosphate bond) is broken.

4. **Formation of ADP and Inorganic Phosphate**:
- The breakdown of ATP results in the formation of ADP (Adenosine Diphosphate) and an inorganic phosphate (Pi). This reaction can be summarized as:
\[ \text{ATP} \rightarrow \text{ADP} + \text{Pi} + \text{Energy} \]

5. **Conclusion**:
- The reason ATP is considered a high-energy compound is due to the significant amount of energy (7.3 kcal/mol) released when the bond between the last phosphate group and the rest of the molecule is broken, making it a crucial energy currency in biological systems.

### Final Answer:
ATP is considered a high-energy compound because under cellular conditions, 7.3 kcal per mole of energy is released when the bond is broken between the last phosphate group and ADP.

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