Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is primarily absorbed in the jejunum portion of the small intestine?

1. Water and minerals

2. Proteins and carbohydrates

3. Fatty acids

4. Nucleic acids

The correct answer is: Proteins and carbohydrates

The correct answer highlights the primary role of the jejunum in nutrient absorption. The jejunum is specifically adapted for the absorption of a significant portion of digested nutrients, particularly proteins and carbohydrates. In the jejunum, the epithelial cells possess a large surface area due to the presence of villi and microvilli, which enhance the absorption process. Proteins are broken down into amino acids or small peptides, and carbohydrates are reduced to simple sugars such as glucose, both of which are absorbed efficiently in this segment of the intestine. The absorption of water and minerals takes place mainly in the ileum and the large intestine, while fatty acids are primarily absorbed in the ileum after being emulsified by bile salts earlier in the digestion process. Nucleic acids have a more minor role in absorption in the small intestine, and their breakdown products, such as nucleotides, are also absorbed but not as predominantly as proteins and carbohydrates in the jejunum. Therefore, the focus on proteins and carbohydrates emphasizes the jejunum's critical function in the digestive system.