Question

Which of the following statements about the digestion of starch is correct?

• A. The digestion of starch by -amylase is an endergonic process
• B. The digestion of starch by -amylase is an exergonic process
• C. The Gibbs free energy for the digestion of starch by -amylase is positive
• D. Starch digestion releases glucose which is actively transported from the epithelial cells into the blood

Answer 1

The correct option is B The digestion of starch by -amylase is an exergonic process

All digestive reactions are hydrolytic reactions. They are exergonic processes that do not require energy but release it. Alpha-amylase hydrolyses the 1, 4-glycosidic bonds that make up the long chains of the starch molecules. Other enzymes complete the digestion. The Gibbs free energy change for the reaction is sufficiently negative to push the equilibrium to the side of hydrolysis. The glucose released from the complete digestion of starch is absorbed into epithelial cells of the intestine by an energy-dependent process and is transported into the blood by facilitated diffusion.