In the conversion of pyruvic acid to acetyl coenzyme A, pyruvic acid is reduced.

Answer

### Step-by-Step Solution:

1. **Understanding the Context**: The question pertains to the biochemical process that occurs when pyruvic acid is converted to acetyl coenzyme A (acetyl CoA). This process is part of cellular respiration, specifically linking glycolysis to the Krebs cycle.

2. **Entry of Pyruvic Acid**: Pyruvic acid, which is produced from glycolysis, enters the mitochondria through a transport protein. This is the first step in its conversion to acetyl CoA.

3. **Oxidative Decarboxylation**: Once inside the mitochondria, pyruvic acid undergoes a process called oxidative decarboxylation. This process involves two main actions:
- **Oxidation**: Pyruvic acid is oxidized, meaning it loses electrons and hydrogen atoms. This is a crucial step as it prepares the molecule for further reactions.
- **Decarboxylation**: During this step, a molecule of carbon dioxide (CO2) is removed from pyruvic acid. This results in the formation of an acetyl group.

4. **Formation of Acetyl CoA**: After the removal of CO2, the acetyl group that remains combines with coenzyme A (CoA), which contains sulfur. This reaction forms acetyl coenzyme A (acetyl CoA), which is an important substrate for the Krebs cycle.

5. **Conclusion**: In summary, during the conversion of pyruvic acid to acetyl CoA, pyruvic acid is oxidized (not reduced) as it loses electrons and a carbon atom in the form of CO2.

### Final Answer:
In the conversion of pyruvic acid to acetyl coenzyme A, pyruvic acid is oxidized, not reduced.

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