This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Which of the following is not secreted by the pancreas \nSelect and explain. \nA. Procarboxypeptidase, B. Trypsinogen, C. Phospholipase A, D. Pepsinogen', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Pancreatic\xa0juice\xa0is\xa0secreted\xa0most\xa0abundantly\xa0in response to the presence of chyme in the upper portions\xa0of the small intestine, and the characteristics of the pancreatic juice are determined to some extent by the types of food in the chyme. (The pancreas also secretes insulin, but this is not secreted by the same pancreatic tissue that secretes intestinal pancreatic juice. Instead, insulin is secreted directly into the blood-not into the intestine-by\xa0 the\xa0 islets\xa0of\xa0Langerhans\xa0that\xa0occur\xa0in\xa0islet\xa0patches throughout the pancreas). The\xa0most\xa0important\xa0of\xa0the\xa0pancreatic\xa0enzymes\xa0for digesting proteins are trypsin, chymotrypsin, and carboxypolypeptidase. By far the most abundant of these is trypsin.\nTrypsin\xa0and\xa0chymotrypsin\xa0split\xa0whole\xa0and\xa0partially digested proteins into peptides of various sizes but do not cause\xa0 release\xa0 of\xa0 individual\xa0 amino\xa0 acids.\xa0However,\xa0 carboxypolypeptidase\xa0splits\xa0 some\xa0peptides\xa0into\xa0individual amino acids, thus completing digestion of some proteins all the way to the amino acid state. The pancreatic enzyme for digesting carbohydrates is\xa0 pancreatic\xa0 amylase,\xa0which\xa0hydrolyzes\xa0starches, glycogen,\xa0and\xa0most\xa0other\xa0carbohydrates\xa0 (except cellulose)\xa0to\xa0form\xa0mostly\xa0disaccharides\xa0and a\xa0few trisaccharides.The main enzymes for fat digestion are\n(1) pancreatic lipase, which is capable of hydrolyzing neutral fat into\xa0 fatty\xa0 acids\xa0 and\xa0 monoglycerides;\xa0\n(2)\xa0cholesterol esterase, which causes hydrolysis of cholesterol esters;and\xa0\n(3)\xa0 phospholipase,\xa0 which\xa0splits\xa0fatty\xa0acids\xa0 from phospholipids.\nWhen\xa0first\xa0synthesized\xa0in\xa0the\xa0pancreatic\xa0cells,\xa0the proteolytic\xa0digestive\xa0enzymes\xa0are\xa0in\xa0the\xa0inactive\xa0forms trypsinogen, chymotrypsinogen, and procarboxypolypeptidase, which are all inactive enzymatically. They become activated only after they are secreted into the intestinal tract. Trypsinogen is activated by an enzyme called enterokinase, which is secreted by the intestinal mucosa when chyme comes in contact with the mucosa. Also, trypsinogen can be autocatalytically activated by trypsin that has already been formed from previously secreted trypsinogen.\xa0 Chymotrypsinogen\xa0is\xa0 activated\xa0by\xa0trypsin to\xa0form chymotrypsin, and procarboxypolypeptidase is activated in a similar manner.', 'role': 'assistant'}]