Stomach Digestion: Breakdown of Bolus - Carbohydrates, Proteins & Fats

1. Carbohydrates:

- Salivary amylase continues to break down carbohydrates in the stomach.

- Gastric acid denatures salivary amylase and stops its action when the pH drops below 4.

2. Proteins:

- Pepsin is secreted in an inactive form called pepsinogen. Hydrochloric acid (HCl) activates pepsinogen into pepsin.

- Pepsin cleaves peptide bonds on the carboxyl side of aromatic amino acids (phenylalanine, tyrosine, and tryptophan).

3. Fats:

- Stomach has no enzymes to digest fats. However, fats may undergo some physical changes:

- Some triglycerides may be hydrolyzed to fatty acids and glycerol by gastric lipase.

- Emulsification of fats into smaller droplets by mechanical agitation of stomach contractions.

4. Nucleic Acids:

- Nucleases may hydrolyze some dietary nucleic acids to form nucleotides in the stomach.