Question

List enzymes and their action on food in the stomach and intestine.

Answer 1

In human beings, the digestive system consists of the alimentary canal and the associated glands. These glands help in the digestion of food. The process of digestion of food is accomplished by the mechanical and chemical processes.

Complete answer:
Enzymatic action in the stomach:
The proenzyme pepsinogen secreted by the parietal cells of gastric glands, on the exposure to hydrochloric acid gets converted into the active enzyme pepsin. The pepsin is the proteolytic enzyme of the stomach.
Pepsin converts proteins into proteases and peptones (peptides).
Enzymatic action in the intestine:
Proteins, proteases and peptones (partially hydrolysed proteins) in the chyme reaching the intestine are acted upon by the proteolytic enzymes of pancreatic juice. Proteins, peptones and proteoses are converted into dipeptides upon the action of trypsin/ chymotrypsin.
Carbohydrates in the chymes are hydrolysed by pancreatic amylase into disaccharides. Polysaccharides (starch) is converted into disaccharides on the action of amylase or amylopsin.
Fats are broken down by lipases with the help of bile into di- and monoglycerides. Fats upon the action of lipase are converted into diglycerides and monoglycerides.
Nucleases in the pancreatic juice act on nucleic acids to form nucleotides.
The enzymes in the succus entericus act on the ends products of the above-mentioned reactions to form the respective simple absorbable forms.
Dipeptides are converted into amino acids on the action of dipeptidases. Maltose is converted into two molecules of glucose on the action of maltase enzymes. Lactose is converted into glucose and galactose by lactase. Sucrose is converted into fructose and glucose by sucrase.

Additional Information:
The mucosa of the stomach has gastric glands. Gastric glands have three major types of cells namely

Mucous neck cells which secrete mucus.
Peptic or chief cells which secrete the proenzyme pepsinogen.
Parietal or oxyntic cells which secrete hydrochloric acid and intrinsic factors.

Note:
The pancreatic juice contains inactive enzymes- trypsinogen, chymotrypsinogen, procarboxypeptidase, analyses, lipases and nucleases. Trypsinogen is activated by enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin, which in turn activates the other enzymes in the pancreatic juice.