Carbs

• Polysaccharides: 20+ monosaccharides linked together, starch, cellulose, and glycogen
• Glycogen: glucose linked together in liver and muscle, storage form
• Monosaccharides are the only carbs our body can directly digest (glucose, fructose, galactose)
• Disaccharides: sucrose, lactose, maltose
• Glycoproteins: protein with a sugar attached, Hgb A1C: marker of blood sugar levels
• Red blood cells and the brain use carbs for energy
• Stach contains amylose and amylopectin
• Amylose: linear chains of glucose molecules attached via alpha 1,4-glycosidic bonds
• Amylopectin: branched chain of glucose molecules attached via alpha 1,6 glycosidic bond
• Starch has a reducing end and a non-reducing end
• Alpha-amylase: hydrolyzes 1,4 glycosidic bonds
• Amylose is digested into maltotriose and maltose
• Amylopectin is digested into alpha-limit dextrins: branches smaller polysaccharide
• Alpha-glucosidases: enzymes released from the brush border to break down sugars
• Sucrase-isomaltase: enzyme that breaks down disaccharides and maltotriose
• Maltase-glucoamylase: breaks down dextrin
• Isomaltase: only enzyme able to break alpha 1,6 linkages
• Diabetic drugs targe alpha-glucosidases to limit the absorption of sugars
• Sodium glucose transporter (SGLT1) is on the apical side (brush border) and moves glucose into the submucosa
• GLUT5 is on the apical side and moves fructose into the submucosa
• GLUT2 is on the basal lateral side and moves glucose into the blood stream where the sugar goes to the liver
• Resistant starch: fraction of dietary starch is not digested because of reduced access of digestive enzymes to the starch molecule
• Liver is the initial storage site for monosaccharides
• GLUT1 and GLUT3 are in the brain and RBCs, they do not require insulin and have high affinity
• GLUT2: is in kidney, intestine and liver. they do not require insulin and have low affinity
• GLUT4: is in skeletal muscle, cardiac muscle and adipose tissues. they require insulin to be activated
• GLUT5: is in intestinal cells and are specific for fructose