An advertisement promotes energy bars containing fructose as ideal food to take on extreme mountain-climbing expeditions. Which of the following statements concerning fructose absorption is true?

Question

Quizplus · Accepted Answer

Fructose is absorbed into intestinal epithelial cells by facilitated transport via the GLUT5 transporter, which does not require energy. Carbohydrate absorption occurs at enterocytes of the upper region of small intestinal villi. Fructose absorption is via the facilitated transporters GLUT5 across the apical enterocyte membrane and GLUT2 across the basolateral enterocyte. Glucose and galactose on the other hand are transported into enterocytes on carriers in combination with a sodium ion. 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, 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.

An Advertisement Promotes Energy Bars Containing Fructose as Ideal Food