Pepsinogen is an inactive enzyme released by the gastric gland of stomach.
On which nutrient does it act upon?

Explanation

**Step-by-Step Solution:**

1. **Understanding Pepsinogen**: Pepsinogen is an inactive enzyme (also known as a proenzyme) that is secreted by the gastric glands in the stomach. It is important to note that it does not have any enzymatic activity in its inactive form.

2. **Activation of Pepsinogen**: When pepsinogen enters the acidic environment of the stomach, it comes into contact with hydrochloric acid (HCl). The acidic conditions (specifically the hydrogen ions from HCl) trigger a transformation of pepsinogen into its active form, which is called pepsin.

3. **Function of Pepsin**: Once activated, pepsin acts as a digestive enzyme. Its primary role is to break down proteins into smaller peptides. This process is crucial for protein digestion, as proteins in food need to be broken down into smaller units to be absorbed by the body.

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