Answer
The correct answer is $c. secretin.$
Work Step by Step
The correct answer is $c. secretin.$
$Secretin$ is not an enzyme; it is a hormone produced by the duodenum (part of the small intestine) in response to the presence of acidic chyme (partially digested food) in the stomach. Secretin plays a role in regulating the digestive process by stimulating the pancreas to release bicarbonate-rich pancreatic juice into the small intestine. This bicarbonate-rich fluid helps neutralize the acidic chyme coming from the stomach.
The other options mentioned are enzymes:
$a. Chymotrypsin$ - An enzyme produced by the pancreas that digests proteins in the small intestine.
$b. Enterokinase$ - An enzyme produced in the small intestine that activates trypsinogen to trypsin, which is involved in protein digestion.
$d. Pepsin$ - An enzyme produced in the stomach that begins the digestion of proteins by breaking them down into smaller peptides.
$e. Nucleosidase$ - An enzyme that catalyzes the hydrolysis of nucleosides into nucleic acid components (e.g., purines and pyrimidines).
So, among the options provided, $secretin$ is not an enzyme but rather a hormone involved in regulating digestion.
