Problem 4 - Campbell Biology

Question

Which of the following is not a major activity of the stomach? (A) storage (B) HCl production (C) nutrient absorption (D) enzyme secretion

Step-by-Step Solution

Answer

(C) Nutrient absorption

Step 1: Identify major activities of the stomach

The stomach is primarily responsible for storage of food, production of hydrochloric acid (HCl), and secretion of enzymes involved in digestion.

Step 2: Analyze each option

(A) is correct because the stomach stores food. (B) is also correct as the stomach produces hydrochloric acid (HCl). (C) is incorrect because nutrient absorption primarily occurs in the small intestine, not the stomach. (D) is correct because the stomach secretes digestive enzymes.

Step 3: Determine the correct answer

Based on the analysis, (C) Nutrient absorption is not a major activity of the stomach.

Key Concepts

Food Storage

The primary function of the stomach includes the storage of food. When you eat, the stomach acts as a reservoir that holds ingested food until it is ready to be processed further. This allows you to consume a meal without the immediate need to digest everything at once. Your stomach can expand significantly to accommodate large amounts of food due to the flexibility of its walls. This ability is vital for allowing the staggered release of food into the small intestine, ensuring efficient digestion and nutrient absorption downstream.

Hydrochloric Acid Production

Hydrochloric acid (HCl) production is one of the key functions of the stomach. The stomach lining contains specialized cells known as parietal cells. These cells secrete HCl, which creates an acidic environment within the stomach. This acidic environment serves several important purposes:
• It helps to break down food particles
• Kills harmful bacteria and pathogens
• Activates the enzyme pepsin, which is crucial for protein digestion
Without adequate production of hydrochloric acid, food digestion would be significantly impaired, leading to various digestive problems.

Enzyme Secretion

The stomach secretes several important digestive enzymes that play a pivotal role in breaking down food. Chief cells in the stomach lining produce pepsinogen, an inactive enzyme, which is then activated to pepsin by the acidic environment created by HCl. Pepsin is essential for the digestion of proteins into smaller peptides. Additionally, gastric lipase is produced to assist in the digestion of fats, though it plays a lesser role compared to enzymes in the small intestine. Enzyme secretion facilitates the chemical breakdown of food, preparing it for further digestion and nutrient absorption in the intestines.

Nutrient Absorption

Unlike the processes of food storage, hydrochloric acid production, and enzyme secretion, nutrient absorption is not a major activity of the stomach. Most nutrient absorption occurs in the small intestine. The stomach's main role is to prepare food for this process by breaking it down into a semi-liquid form known as chyme. Once chyme enters the small intestine, it is mixed with bile and pancreatic juice to allow for efficient nutrient absorption. While the stomach does absorb certain substances such as alcohol and some medications, it is not the primary site for nutrient absorption.