Gastrointestinal System

The stomach produces pepsinogen which activates to pepsin which begins the digestion of protein. Fat is not significantly digested in the stomach (gastric lipase initiates the digestion of milk protein).

Amino acids are the smallest molecules resulting from protein hydrolysis. Some two amino acid units (dipeptides) and three amino acid units (tripeptides) can also be absorbed from the gut.

The liver is not part of the digestive tract (chyme does not pass through it); rather, it contributes bile to the gut contents via the common bile duct.

Producing smaller droplets of fat increases the surface area available for lipase and allows digestion to proceed faster.

Hydrolysis refers to the splitting (lysis) of large molecules into smaller ones using water (hydro).

The pH of the stomach contents is about 2 (strongly acidic), while the pH of the small intestine is about 8 (weakly alkaline). The numbers in choices C and D are wrong. Thus B is the best answer.

Humans are unable to hydrolyse cellulose; blood clotting proteins are synthesised in the liver; intrinsic factor is secreted by the stomach.

The large surface area allows the products of digestion ample opportunity to make contact with the absorbing surface.

The crypts produce the secretion known as intestinal juice.

Gut contents are outside of the body until absorbed through the mucosal lining.