Search results
Results from the WOW.Com Content Network
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth , stomach , pancreas , and duodenum , before being able to be absorbed into the ...
In molecular biology, protein catabolism is the breakdown of proteins into smaller peptides and ultimately into amino acids. Protein catabolism is a key function of digestion process. Protein catabolism often begins with pepsin , which converts proteins into polypeptides.
Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. In infants and toddlers, gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach.
H + and Cl − are secreted by the parietal cells into the lumen of the stomach creating acidic conditions with a low pH of 1. H + is pumped into the stomach by exchanging it with K +. This process also requires ATP as a source of energy; however, Cl − then follows the positive charge in the H + through an open apical channel protein.
Enteropeptidase (also called enterokinase) is an enzyme produced by cells of the duodenum and is involved in digestion in humans and other animals. Enteropeptidase converts trypsinogen (a zymogen) into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes.
The breakdown of protein begins in the stomach through the actions of hydrochloric acid, and the enzyme pepsin. The stomach can also produce gastric lipase, which can help digesting fat. The contents of the stomach are completely emptied into the duodenum within two to four hours after the meal is eaten.
50-60% of total gastric acid secretion occurs during this phase. The gastric phase is a period in which swallowed food and semidigested protein (peptides and amino acids) activate gastric activity. Ingested food stimulates gastric activity in two ways: by stretching the stomach and by gastric contents stimulating receptors in the stomach. [2]
Also, the secretion of secretin is increased by the products of protein digestion bathing the mucosa of the upper small intestine. [22] Secretin release is inhibited by H 2 antagonists, which reduce gastric acid secretion. As a result, if the pH in the duodenum increases above 4.5, secretin cannot be released. [23]