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Sample MCAT question: pH in the stomach

  • This MCAT practice question is supplied courtesy of Next Step Test Preparation. Next Step is national leader in MCAT test prep and focuses exclusively on providing one-on-one, personalized test prep for the MCAT.

The pH inside the stomach is very closely regulated. Which of the following is a major function for the pH in the stomach?

A) Neutralizing the acidity of the chyme entering it

B) Denaturing proteins to allow for digestive processes

C) Activating trypsinogen into the active form

D) Establishing a proton gradient for ATP production

Explanation:

This question tests your knowledge of the physiological functions that result from the low pH within the stomach cavity. While the acid environment serves several functions, one important one is denaturing the tertiary structure of proteins in the food. This lets proteases break up the protein into smaller peptides.

A) The chyme is the substance that leaves the stomach, not enters it.

B) Correct

C) Trypsinogen is found in the small intestine, not the stomach.

D) A proton gradient is used for ATP production in the mitochondria, not the lumen of the stomach.

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