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Ch. 41 - Animal Nutrition
Chapter 41, Problem 5

If you put the following events in the order they occur in the human digestive system, the third event in the series would be a. Cells in gastric pits secrete protons. b. Pepsin activates pepsinogen. c. HCl activates pepsinogen. d. Partially digested food enters the small intestine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gastric Secretion

Gastric secretion involves the release of digestive substances from the stomach lining, primarily hydrochloric acid (HCl) and digestive enzymes. HCl creates an acidic environment that is crucial for activating pepsinogen, an inactive enzyme secreted by gastric cells. This process is essential for protein digestion and prepares the food for further breakdown in the small intestine.
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Pepsinogen Activation

Pepsinogen is an inactive precursor of the enzyme pepsin, which is responsible for breaking down proteins into smaller peptides. The activation of pepsinogen occurs in the acidic environment of the stomach, where HCl converts it into active pepsin. This step is critical for initiating protein digestion before the food moves into the small intestine.
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Digestive Process Sequence

The digestive process follows a specific sequence of events that begins in the mouth and continues through the stomach and intestines. Understanding this sequence is vital for identifying the order of events in digestion. In this case, the sequence includes gastric secretion, activation of digestive enzymes, and the movement of partially digested food into the small intestine for further digestion and nutrient absorption.
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