Ptyalin is inactive by a component of gastric juice

Options

A. Rennin
B. Pepsin
C. Mucus
D. HCl

Answer

### Step-by-Step Solution:

1. **Identify the Component in Question**: The question refers to "Ptyalin," which is another name for salivary amylase. It is an enzyme produced in the saliva that helps in the digestion of starch.

2. **Function of Ptyalin**: Salivary amylase (ptyalin) converts starch into maltose. This process occurs primarily in the mouth, where food is mixed with saliva.

3. **Pathway of Digestion**: After the food is chewed and mixed with saliva, it forms a bolus and travels down the esophagus to the stomach.

4. **Environment in the Stomach**: Upon reaching the stomach, the food is mixed with gastric juice, which contains hydrochloric acid (HCl).

5. **Effect of Hydrochloric Acid**: The secretion of HCl in the stomach creates an acidic environment. This acidity is crucial because it inactivates salivary amylase. Thus, ptyalin becomes inactive in the presence of HCl.

6. **Conclusion**: Therefore, the component of gastric juice that inactivates ptyalin (salivary amylase) is hydrochloric acid (HCl).

### Final Answer:
The component of gastric juice that inactivates ptyalin is **hydrochloric acid (HCl)**.

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