Ion which promotes glucose absorption in the gut region: September 2007
**Core Concept**
The process of glucose absorption in the gut region involves the coordinated action of several nutrients, hormones, and ion transport mechanisms. In the small intestine, glucose is absorbed into the bloodstream through a sodium-glucose cotransporter (SGLT1) mechanism, which relies on the presence of sodium ions (Na+) to facilitate glucose uptake.
**Why the Correct Answer is Right**
The correct answer is sodium ions (Na+). Sodium ions play a crucial role in promoting glucose absorption by creating an electrochemical gradient that drives glucose uptake into the intestinal epithelial cells. The sodium-glucose cotransporter (SGLT1) uses the energy from the sodium gradient to transport glucose into the cell against its concentration gradient. This process is essential for the efficient absorption of glucose from the gut into the bloodstream. The sodium-glucose cotransporter is specifically located in the apical membrane of the intestinal epithelial cells, where it can interact with sodium ions and glucose molecules.
**Why Each Wrong Option is Incorrect**
* **Option A:** Chloride ions (Cl-) are not directly involved in glucose absorption in the gut region. While chloride ions play a role in maintaining the integrity of the intestinal epithelial barrier, they are not essential for glucose uptake.
* **Option B:** Calcium ions (Ca2+) are important for muscle contraction and other cellular processes but are not directly involved in glucose absorption in the gut region.
* **Option C:** Potassium ions (K+) are involved in maintaining the resting membrane potential and are not directly involved in glucose absorption in the gut region.
**Clinical Pearl / High-Yield Fact**
The sodium-glucose cotransporter (SGLT1) is a key transporter involved in glucose absorption in the gut region, and its activity is essential for maintaining normal glucose homeostasis. Inhibitors of SGLT1, such as phlorizin, can impair glucose absorption and are used in the treatment of diabetes mellitus.
**Correct Answer:** A. Sodium ions (Na+)