The manufacturer of energy bars makes claim that the fructose contained in their bars serves as an ideal source of energy for extreme mountain climbing and mountain biking expeditions. Which of the following statements concerning fructose reflects the basis for these claims?

Question

Quizplus · Accepted Answer

Fructose is absorbed into intestinal epithelial cells by facilitated transport, which does not require energy, making it an efficient energy source. Carbohydrate absorption occurs at enterocytes of the proximal duodenum. Fructose absorption into the blood occurs via the facilitated transporters GLUT5 across the apical enterocyte membrane and then via GLUT2 across the basolateral membrane. Glucose and galactose on the other hand are transported into enterocytes via the actions of the sodium-dependent transporter, SGLT1. The energy for this secondary active transport is provided by the electrochemical sodium gradient that is created by Na+/K+-ATPases. Experimental conditions that collapse the sodium electrochemical gradient, such as with hypoxia, or poisoning of the Na+/ K+-ATPase by ouabain, inhibit glucose, but not fructose absorption. Nevertheless, the physiological importance of saving energy under extreme conditions such as mountain climbing through the use of fructose as energy source is questionable given that intestinal fructose absorption is much slower than absorption of glucose and galactose.

The Manufacturer of Energy Bars Makes Claim That the Fructose