This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Digestion and Absorption, Subject name: Physiology
Salivary amylase is Inactivated by - 
Select and explain. 
A. Enteropeptidase, B. Low pH of the stomach, C. High pH of the intestine, D. None
B: Low pH of the stomach
Answer: B: Low pH of the stomach 
Explanation: Ans. is 'b' i.e., Low pH of the stomach o Saliva contains amylase (salivary amylase or ptyalin), which hydrolyzes starch into disaccharide maltose and a mixture of oligosaccharides. o Its action is very short- lasting because it is inactivated by acidic gastric pH (< 3) shortly after entering the stomach. Salivary amylase optimally active at pH of around 6.9 (6.5 - 7). o It is inactive at a pH below 4.5.