Define digestion in one sentence.

Explanation

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

1. **Understanding Digestion**: Digestion is a biological process that involves breaking down food substances.

2. **Catabolic Process**: It is specifically a catabolic process, meaning it involves the breakdown of complex molecules into simpler ones.

3. **Non-Diffusible to Diffusible**: The purpose of digestion is to convert non-diffusible products (which cannot easily pass through cell membranes) into diffusible and absorbable products.

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