Final answer:
The absorption of glucose in the intestine does not involve the phosphorylation of glucose upon entry into the epithelial cells. Instead, glucose is absorbed through secondary active transport, brush border enzyme activity, and facilitated diffusion. The correct option is a) phosphorylation of glucose as soon as it enters the epithelial cells.
Step-by-step explanation:
The absorption of glucose from the gut through the intestinal epithelial cells into the blood involves all of the following EXCEPT: phosphorylation of glucose as soon as it enters the epithelial cells. This option is not a part of the glucose absorption process in the intestine. Instead, glucose absorption involves the following steps:
- Glucose is transported across the brush border membrane via the sodium-dependent glucose transporter (SGLT1), which is a form of secondary active transport involving the co-transport with sodium ions.
- The disaccharides are cleaved into monosaccharides by brush border enzymes prior to absorption.
- Then, glucose leaves the epithelial cells through the basolateral membrane via facilitated diffusion and enters the capillaries.
The active transport of glucose from the lumen into the cell uses energy derived from the Na+/K+ ATPase pump, which maintains a low concentration of Na+ inside the cell by exchanging Na+ for K+ and hydrolyzing ATP. This active transport allows glucose to move against its concentration gradient. The correct option is a) phosphorylation of glucose as soon as it enters the epithelial cells.