Biology Forums - Study Force

1. What is the normal pH of the stomach lumen?

I know its pH level 2, ranges between mostly 1-3. I don;t knw question 2 and 3.

2. What happens to the activity of pepsin when pH is increased to 7.0?

3. What happens to the activity of pepsin when pH is increased to 9.0?

Could you provide the exercise # and activity information?

Sorry,
Exercise 8: Chemical and Physical Processes of Digestion - Activity 3: Assessing Pepsin Digestion of Protein

See if these correspond to the questions, livestrong136.

1. The optimum pH matches the pH secreted by gastric glands. Gastric juice is also about pH 2.

2. Since the pH of the mouth is closer to neutrality, you would expect pepsin to be slightly active but not as active as it is in the stomach at pH 2.

3. The subunit products of digestion are peptides and amino acids.

I know for question #3,

- pepsin is irreversibly denatured (enzymes break down).

I am confused though because any ph above for this will denature all proteins, so why ask questions about 7 and 9. I assume, at ph7, the activity of pepsin become inactive but is a reversible process but at 9, its irreversibly denatured. Let me know what you think?

I think what they're hinting on is will the enzyme denature at a basic (alkaline) pH. I'm not 100% sure, but I've always learned that enzymes denature in acidic environments.