This is What Happens to Antacids on the SAT

N.B: This is for SAT Subject Test: Biology E/M

---

The graph above shows the relationship between pH and the activity of two digestive enzymes pepsin and trypsin. These enzymes work in two different parts of the human digestive system, the stomach and the small intestine.

Questions:

1. How would taking an antacid affect the activity of pepsin?

(A) The activity would decrease because of the pH would increase.
(B) The activity would decrease because of the pH would decrease.
(C) The activity would increase because of the pH would increase.
(D) The activity would decrease because of the pH would decrease.
(E) Taking an antacid would have no affect on the activity of pepsin.

2. Where in the digestive tract would trypsin most likely be found?

(A) mouth
​(B) stomach
(C) small intestine
(D) large intestine
(E) rectum

3. What is the pH at which trypsin works best?

(A) 5.5
(B) 6
(C) 7
(D) 8
(E) 10

4. What is the pH at which pepsin works best?

(A) 0
(B) 2
(C) 4
(D) 6
(E) 8

5. Which of the following statements is true about the digestive enzymes pepsin and trypsin?

(A) Pepsin works best in a basic environment and trypsin works best in an acidic environment.
(B) Pepsin and trypsin work best in acidic environments.
(C) Pepsin and trypsin are both formed in the stomach.
(D) Pepsin works best in an acidic environment and trypsin works best in a basic environment.
(E) Pepsin and trypsin both work well in acidic and basic environments. 

Answer:

1. A.
An antacid would increase the pH in the stomach and decrease the activity of the pepsin.

2. C.
The small intestine neutralizes the acid from the stomach and creates a basic environment. Trypsin works best in a basic environment.

3. D. 
Trypsin has a peak performance at a pH of 8.

4. B.
Pepsin has a peak performance at a pH of 2.

5. D.
The enzymes each have a peak performance based on the pH of where they are found.