AAMC FL Practice Exam

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Study for the AAMC FL Exam. Prepare with comprehensive flashcards and multiple-choice questions, each equipped with hints and explanations. Gear up for your medical school entrance exam!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

Which enzyme begins protein digestion in the stomach?

Amylase
Lipase
Pepsin
Trypsin

The correct answer is: Pepsin

Protein digestion in the stomach is initiated by pepsin, an enzyme specifically designed to break down the peptide bonds in proteins into smaller polypeptides. Pepsin is activated from its inactive precursor, pepsinogen, in the acidic environment of the stomach that is created by gastric acid (hydrochloric acid). The acidic pH not only activates pepsinogen but also enhances the enzyme's ability to degrade protein structures. Amylase, on the other hand, is primarily involved in carbohydrate digestion, breaking down starches into sugars, and is found in saliva as well as pancreatic secretions. Lipase plays a role in lipid digestion, breaking down fats into fatty acids and glycerol, and is also secreted by the pancreas. Trypsin is another enzyme involved in protein digestion but is released by the pancreas and acts in the small intestine rather than in the stomach. Thus, pepsin is uniquely suited to begin the process of protein digestion in the acidic environment of the stomach, making it the correct choice.