The breakdown of complex carbohydrates into glucose is completed in the small intestine during digestion. What protein acts as a catalyst to speed up the reaction?

Amylase is the protein which acts as a catalyst to break complex carbohydrates. Sucrase breaks sucrose into glucose and fructose molecules.

Explanation:

The digestion of carbohydrates starts the earliest in the mouth. Mechanical digestion takes place in the mouth.

When food in the form of chyme, enters in the small intestine from the stomach, the pancreas secrete pancreatic juice. The pancreatic juice is rich in the enzyme, amylase. The enzyme amylase breaks down complex carbohydrates and starch into simpler sugars. Sucrose is converted into glucose and fructose by the enzyme sucrase.