Which food molecules are altered in the stomach?

The stomach plays a vital role in the initial stages of digestion, where it primarily alters carbohydrates, proteins, and fats. Here are the specific food molecules that undergo modifications in the stomach:

Carbohydrates:

1. Starches: Starches are complex carbohydrates found in foods like potatoes, rice, and bread. In the stomach, salivary amylase, an enzyme produced in the mouth, continues to break down starches into smaller units called dextrins. However, the acidic environment of the stomach eventually inactivates amylase, halting the digestion of carbohydrates in the stomach.

Proteins:

1. Pepsinogen Activation: Pepsinogen, an inactive form of the enzyme pepsin, is secreted by chief cells in the stomach. The acidic environment in the stomach converts pepsinogen into active pepsin.

2. Protein Breakdown: Pepsin is the primary enzyme responsible for protein digestion in the stomach. It breaks down proteins into smaller peptide fragments, initiating the process of protein hydrolysis.

Fats:

1. Emulsification: Fats, such as those found in meat, dairy products, and cooking oils, are not directly broken down in the stomach. However, the stomach performs a crucial step called emulsification, which prepares fats for further digestion.

2. Formation of Chyme: The churning motion of the stomach muscles and the presence of gastric juices result in the formation of a semi-fluid mixture called chyme. Chyme contains partially digested food, including emulsified fats, proteins, and carbohydrates.

It's worth noting that while carbohydrates, proteins, and fats undergo initial modifications in the stomach, their complete digestion occurs further along the digestive tract, primarily in the small intestine, where various enzymes and bile play crucial roles in breaking down these nutrients into absorbable components.