Digestion of Carbohydrates Quiz

Digestion begins in the oral cavity with saliva containing α-amylase, which hydrolyzes starch into maltose and oligosaccharides.
Salivary amylase is inactivated at pH 4.0; thus, carbohydrate digestion transitions to the small intestine.
Pancreatic amylase continues the digestion, producing maltose, glucose, and isomaltose (two glucose molecules linked by 1-6 linkage).
Intestinal disaccharidases, including maltase, sucrase, lactase, and isomaltase, further break down sugars.
Lactose intolerance occurs due to lactase deficiency, leading to osmotic diarrhea, affecting over 70% of adults globally.

Absorption methods include active transport (against concentration gradient) and facilitated transport (diffusion).
Glucose and galactose are absorbed actively, requiring specific structural configurations (OH on carbon 2, pyranose ring, methyl group at C5).
Fructose absorption is slower, also involving active transport.
Active glucose absorption relies on the sodium pump, functional in the small intestine and renal tubules.

GLUT1: Ubiquitously distributed; mediates low-level basal glucose uptake essential for cellular respiration. High levels in erythrocytes and barrier tissues, such as the blood-brain barrier.
GLUT2: Bidirectional transporter located in the gut, liver, and pancreatic islets. Allows glucose movement for glycolysis and gluconeogenesis, regulating serum glucose levels in pancreatic beta cells.
GLUT3: Predominantly found in the central nervous system and neurons, it is considered the primary glucose transporter in these tissues.
GLUT4: Located in insulin-responsive tissues including skeletal muscle, adipose tissue, and heart. Critical for glucose uptake in response to insulin.