**Role of acid in our stomach:**

The acid in our stomach plays a crucial role in the process of digestion. It helps in breaking down the food we consume, enabling the absorption of nutrients and providing protection against harmful bacteria. The main acid present in the stomach is hydrochloric acid (HCl), which is secreted by the stomach lining cells called parietal cells.

**1. Activation of enzymes:**
The acid in the stomach helps in activating certain enzymes necessary for digestion. For example, it activates pepsinogen into pepsin, an enzyme that breaks down proteins into smaller peptides. This process is essential for the digestion of proteins.

**2. Breakdown of food:**
The acidic environment in the stomach aids in the breakdown of food into smaller particles. The acid denatures proteins, making them more accessible to digestive enzymes. It also helps in the breakdown of complex carbohydrates and fats.

**3. Optimal pH for enzyme activity:**
The stomach acid creates an acidic pH environment (pH 1-3) that is ideal for the activity of digestive enzymes. The low pH provides an optimum condition for enzymes to function effectively, ensuring proper digestion and absorption of nutrients.

**4. Killing bacteria and pathogens:**
Stomach acid plays a crucial role in protecting our body from harmful bacteria and pathogens that may enter through the food we consume. The highly acidic environment kills most of these microorganisms, preventing infections and diseases.

**5. Activation of vitamin B12:**
The acid in the stomach is responsible for separating vitamin B12 from the proteins in food. This allows vitamin B12 to bind with a compound called intrinsic factor, which is essential for its absorption in the small intestine. Adequate vitamin B12 absorption is necessary for the production of healthy red blood cells and proper nerve function.

In conclusion, the acid in our stomach plays a vital role in the process of digestion. It activates enzymes, breaks down food, creates an optimal pH for enzyme activity, kills bacteria, and facilitates the absorption of essential nutrients. Understanding the role of stomach acid helps us appreciate the complexity of the digestive system and the importance of maintaining a healthy stomach environment.

The acid in our stomach is HCl. Its function is to kill the germs present in the food and it also makes the medium of the food acidic for the enzyme pepsin to act.