Internal respiration is called a physico- chemical process . Why ?

Explanation

**Step-by-Step Solution:**

1. **Definition of Internal Respiration**: Internal respiration refers to the exchange of gases (oxygen and carbon dioxide) between the blood and the body cells. It is a crucial part of the overall respiratory process.

2. **Physical Process - Diffusion**: The first aspect of internal respiration is the physical process of diffusion. Oxygen moves from areas of higher concentration (in the blood) to areas of lower concentration (in the cells) and carbon dioxide moves in the opposite direction. This movement occurs naturally and does not require energy, which is characteristic of physical processes.

3. **Chemical Process - Oxidative Phosphorylation**: The second aspect involves the chemical process of oxidative phosphorylation. In this process, glucose is broken down in the presence of oxygen to produce ATP (adenosine triphosphate), which is the energy currency of the cell. This process involves a series of chemical reactions that release energy.

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