Digestion and absorption of carbohydrates

Digestion and absorption of carbohydrates
  • The first stage in the digestion of carbohydrates takes place in the mouth when the food is chewed.
  • The saliva contains an alpha amylase called ptyalin.
  • This enzyme acts on starch splitting it into dextrin and maltose.
  • Amylase acts best at neutral pH.
  • As soon as the food reaches the stomach it mixes with the acidic gastric juice and amylase activity is inhibited.
  • The digestion of carbohydrates is mainly accomplished in the small intestines where they are subjected to the action of pancreatic amylases and intestinal amylase, sucrase, lactase, maltase and isomaltase present in the intestinal juice.

Starch ------------->maltose + isomaltose
Amylase from saliva, pancreatic and intestinal juise

Maltose --------------------> glucose

Isomaltose -------------> glucose

Sucrose ------------> glucose + fructose

Lactose ------------> glucose+galactose
  • The ultimate products of digestion of carbohydrate are glucose, fructose and galactose. These are absorbed in the intestines. The non-digestible carbohydrates present in the food like cellulose, hemicellulose, pentosans, galactans, fructosans etc., are not acted upon by the digestive juices. They add bulk to the contents of large intestine and are excreted in the faeces. Some of these are fermented by bacteria present in the large intestine.

Last modified: Thursday, 21 June 2012, 9:39 AM