Regarding digestion in the stomach: "How is pepsin involved? Describe the pH of the stomach. How is smooth muscle involved here? What is chyme?" a. Pepsin helps in carbohydrate digestion; the pH is alkaline. b. Pepsin aids in protein digestion; the pH is acidic. c. Pepsin is involved in fat breakdown; the pH is neutral. d. Pepsin contributes to fiber digestion; the pH is basic.