AP BIOLOGY

Detailed explanation-1: -When the acidic chyme enters into the small intestine from stomach, stomach secretes bicarbonate ions in a large amount in the intestine. It acts as a buffer to break down and dilute the acidic content and increases the pH of the chyme. So, that pancreatic digestive enzyme becomes active for further digestion.

Detailed explanation-2: -In the lower digestive tract, bicarbonate secretion not only protects the intestinal mucosal barrier but also is the most important mechanism regulating the acid/alkaline balance apart from kidney function.

Detailed explanation-3: -Chyme is produced in the stomach and transferred to the Intestine for further digestion. Due to the presence of gastric juices, chyme becomes acidic. This acidity can damage the intestines. Hence to neutralize it basic fluid such as sodium bicarbonate is secreted into the intestine.

Detailed explanation-4: -Secretin stimulates the pancreas to secrete basic juice (rich in HCO3–) and helps to neutralize the acidity of the chyme that has entered the small intestine.

Detailed explanation-5: -There are two major functions of chyme – the first is to increase the surface area of food to allow digestive enzymes to complete their work, and the second is to stimulate various digestive glands to release their secretions. The action of enzymes requires direct contact with the molecules of the substrate.