All living organisms retain the enzymatic machinery to partially oxidise glucose without the help of oxygen. This breakdown of glucose to pyruvic acid is called.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Process**: The question states that all living organisms can partially oxidize glucose without the need for oxygen. This indicates a metabolic process that occurs in anaerobic conditions.

2. **Identifying the Breakdown**: The specific breakdown of glucose mentioned in the question is to pyruvic acid. This is a key point as it helps identify the metabolic pathway involved.

3. **Naming the Process**: The process of breaking down glucose (C6H12O6) to pyruvic acid (C3H4O3) is known as glycolysis. This is a well-established metabolic pathway that occurs in both prokaryotic and eukaryotic organisms.

4. **Details of Glycolysis**: Glycolysis is a series of ten enzyme-catalyzed reactions. During this process, one molecule of glucose is converted into two molecules of pyruvic acid. Additionally, glycolysis results in the production of energy in the form of ATP and NADH.

5. **Conclusion**: Therefore, the breakdown of glucose to pyruvic acid in the absence of oxygen is called glycolysis.

**Final Answer**: The breakdown of glucose to pyruvic acid is called glycolysis.

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