What is the names of enzymes produced in different parts of the digestive system and their substrates?

Answer 1

The digestive tract begins at the oral cavity and continues through the pharynx, esophagus, stomach,

small intestine, and large intestine, which opens to the exterior at the anus.

The Oral Cavity

limited digestion of carbohydrates and lipids.

The Tongue

secretion of mucins and the enzyme lingual lipase.

The parotid salivary glands produce a serous secretion containing large amounts of salivary amylase, an enzyme that breaks down starches (complex carbohydrates).

Cells of the submandibular glands secrete a mixture of buffers, glycoproteins called mucins, and salivary amylase.

The primary function of the esophagus is to convey solid food and liquids to the stomach.

The stomach

Disruption of chemical bonds in food material through the action of acids and enzymes,

production of intrinsic factor, a glycoprotein whose presence in the digestive tract is required for the absorption of vitamin B12in the small intestine.

Parietal cells in the stomach secrete hydrochloric acid (HCl).

Chief cells secrete pepsinogen, an inactive proenzyme. Pepsinogen is converted by the acid in the

gastric lumen to pepsin, an active proteolytic enzyme.

Glands in the pylorus produce primarily a mucous secretion, rather than enzymes or acid. In addition, several types of enteroendocrine cells are scattered among the mucus-secreting cells.

Gastrin is produced by G cells, which are most abundant in the gastric pits of the pyloric antrum.

The pyloric glands also contain D cells, which release somatostatin, a hormone that inhibits the release of gastrin.

The stomach is a holding tank in which food is saturated with gastric juices and exposed to stomach acids and the digestive effects of pepsin.

The mucosa of the small intestine produces only a few of the enzymes involved.

The pancreas provides digestive enzymes, as well as buffers that help neutralize chyme.

The liver secretes bile, a solution stored in the gallbladder for subsequent discharge into the small intestine.

Bile contains buffers and bile salts, compounds that facilitate the digestion and absorption of lipids.

Brush border enzymes are integral membrane proteins located on the surfaces of intestinal microvilli.

These enzymes perform the important digestive function of breaking down materials that come in contact with the brush border.

Enterokinase, one brush border enzyme that enters the lumen in this way, does not directly participate in digestion, but it activates a key pancreatic proenzyme, trypsinogen.

Intestinal glands also contain enteroendocrine cells responsible for the production of several intestinal hormones, including gastrin, cholecystokinin, and secretin.

The pancreas is primarily an exocrine organ, producing digestive enzymes and buffers.

The specific pancreatic enzymes involved include the following:

Pancreatic alpha-amylase, a carbohydrase- an enzyme that breaks down certain starches.

Pancreatic alpha-amylase is almost identical to salivary amylase.

Pancreatic lipase, which breaks down certain complex lipids, releasing products (such as fatty acids) that can be easily absorbed. Nucleases, which break down nucleic acids.

Proteolytic enzymes, which break certain proteins apart. The proteolytic enzymes of the pancreas

include proteases, which break apart large protein complexes, and peptidases, which break small peptide chains into individual amino acids.

Duodenal enteroendocrine cells produce the following hormones known to coordinate digestive functions: Secretin is released when chyme arrives in the duodenum. Secretin's primary effect is an increase in the secretion of bile and buffers by the liver and pancreas.

Cholecystokinin (CCK) is secreted when chyme arrives in the duodenum, especially when the chyme contains lipids and partially digested proteins.

Gastric inhibitory peptide (GIP) is secreted when fats and carbohydrates-especially glucose-enter the small intestine.

Vasoactive intestinal peptide (VIP) stimulates the secretion of intestinal glands, dilates regional capillaries, and inhibits acid production in the stomach.

Gastrin is secreted by G cells in the duodenum when they are exposed to large quantities of incompletely digested proteins.

The functions of gastrin include promoting increased stomach motility and stimulating the production of acids and enzymes.

Enterocrinin, a hormone released when chyme enters the small intestine, stimulates mucin production by the submucosal glands of the duodenum.

Phew!