1. Unit 2, Lesson 4 - Enzymes
B – Enzymes are proteins, which are composed of amino acids and contain an active site. The substrate in the reactant the enzyme acts on (not part of the enzyme)
D – Catalase is the enzyme which is not consumed in the reaction. Hydrogen peroxide is the substrate. Water and oxygen are the products of the reaction.
C – Galactose increases and lactase remains the same.
D – Substrate is already in excess and not the limting factor in the reaction.

2. Unit 2, Lesson 4 – Enzymes Part A Answer:
The graph shows that pepsin functions best in low pH (acidic environment) suggesting that the stomach has a pH between 2 and 3. Trypsin functions best at a pH of about 6 or 7, suggesting that the pH of the small intestine is about neutral.

3. Unit 2, Lesson 4 – Enzymes Part B Answer:
When it travels to the small intestine, pepsin will become denatured by the high pH level. It will no longer catalyze the breakdown of protein.

4. Unit 2, Lesson 4 – Enzymes Part C Answer:
The advantage to having two enzymes is that each enzyme can function in the specific environments of the stomach and small intestine. At least one enzyme functions in each part of the digestive tract ensuring the complete digestion of the proetein in food.