Which statement best describes how a catalyst can speed up a chemical reaction ? a. the catalyst makes lower energy pathways available. b. the catalyst increases the concentration of products. c. the catalyst binds to enzymes to release substrates. d. the catalyst increases the concentration of reactants.

Which of these has happened to your food by the time it reaches your small intestine? a. all the macromolecules have been broken down completely. b. lipids and starches have been partially broken down. c. starches and proteins have been partially broken down. d. proteins and lipids have been broken down into subunits.