Which of the following sugars is absorbed from the small intestine by facilitated diffusion?
A. Glucose
B. Galactose
C. Fructose
D. Sucrose
The
answer is C.
Facilitated diffusion is the major
transport route for fructose. The duodenum and jejunum are the principal sites
of carbohydrate absorption in humans. Digestion of carbohydrates is
accomplished by amylase and brush border enzymes and results in a mixture of
glucose, fructose, and galactose. A common sodium-dependent secondary active
transporter absorbs glucose and galactose. Sucrose and lactose are
disaccharides that break down into glucose and fructose, and glucose and
galactose, respectively.
