Starch is hydrolyzed in the mouth by:
Correct Answer: Ptyalin
Description: Ans. (b) PtyalinRef: Guyton's physiology 11th ed./ 793* Saliva contains two major types of protein secretion:# Serous secretion- contains ptyalin, an enzyme for digesting starches.# Mucus secretionGlandSecretionContentFunctionParotid glandSerous typePtyalinDigest starchesSubmandibular glandSerous and mucous typeMucinLubricating and for surface pro- tective purposesBuccal glandOnly mucusMucinLubricating* Saliva has a pH between 6.0 and 7.0, a favorable range for the digestive action of ptyalin.* The activity of the salivary amylase is blocked by acid of the gastric secretions due to low pH.* But before food and its accompanying saliva become completely mixed with the gastric secretions, as much as 30 to 40% of the starches will have been hydrolyzed mainly to form maltose.* In small intestine the remaining starch Digestion takes place by Pancreatic Amylase. Pancreatic secretion is almost identical in its function with the a-amylase of saliva but is several times more powerful.* Hence, within 15 to 30 minutes after the chyme empties from the stomach into the duodenum and mixes with pancreatic juice, nearly all the carbohydrates will have become digested.
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