Digestion And Absorption Of Carbs Flashcards
Cellulose
-glucose polymer cannot be digested by mammalian
enzymes
-fiber
-helps bowel movement, metabolic process and controlling insulin release
Dietary carbs mostly come from…
Starch
➡️amylose and amylopectin
Amylopectin made up of what type of bonds
-α-1,4 Glycosidic Bonds
-α-1,6 Glycosidic Bonds
Amylose made of what type of bonds
α-1,4 Glycosidic Bonds
Salivary α-Amylase
“Ptyalin”
-Mainly secreted by extrinsic glands
-Only targets the α-1,4 glycosidic bonds and breaks down Amylopectin and Amylose
Amylose is broken down into…
-maltose➡️ disaccharides
-maltitriose➡️ oligosaccharides
- α-Limit dextrins →oligosaccharides
Digestion starts in _ and continues in GI tract all the way to _
Oral cavity; stomach
Oral cavity → Pharynx → esophagus → Stomach
Salivary amylase is inactivated by…
Gastric acid
Digestion of carbs in pancreas
-Acinar cells → Pancreatic Amylase →hydrolyses α-1,4 Glycosidic Bonds
-→ Maltose
- → Matlotriose
-→ α-Limit dextrins
-CCK= Cholecystokinin
-Stimulate acinar cells to produce pancreatic amylase
-Relaxes the Sphincter of Oddi → ejection of the pancreatic amylase to the duodenum
Digestion of carbs in small intestine
-Enterocytes→ epithelial cell found in the small intestine
-Most of the absorption occurs in the small intestine
-Water and electrolytes can be absorbed from the large intestine
-Structural Modifications that increase surface area in the small intestine →↑Digestion and ↑Absorption
-Circular Folds o Villi
-Microvilli
-Enterocyte
➡️little cytoplasmic extensions
➡️⬆️the surface area for chemical digestion and absorption
➡️microvilli
➡️high concentration of brush border enzymes
Brush border enzymes of small intestine
-Lactase
-Maltase-glucoamylase
-Sucrase
-isomaltase
Lactase
-Lactose= disaccharides = Glucose-Galactose
-lactase
➡️breaks down the bond between Glu-Gal
➡️Glu, Gal
Maltase
-= Glucoamylase
-Maltase → breaks down the bond Glu-Glu
-Maltose → 2 Glu
-Maltotriose →3 Glu
Sucrase-isomaltase
-Sucrase → breaks down Maltose, Maltotriose, some α- Limit dextrins and Sucrose
-Sucrose = Glucose-Fructose
Isomaltase
-Targets α-1,6 Glycosidic Bonds o →
-α-Limit dextrin → Glu, Glu, …
From the lumen to enterocyte
Monosaccharides’ Uptake across the Apical Membrane (From Lumen to Enterocyte)
-GLUT-5
-Fructose
-SGLT
-Glucose
-Galactose
From the lumen to enterocyte
Monosaccharides’ Uptake across the Apical Membrane (From Lumen to Enterocyte)
-GLUT-5
-Fructose
-SGLT
-Glucose
-Galactose
From the lumen to enterocyte: fructose uptake
-Facilitated Diffusion by GLUT-5
-GLUT-5= Glucose Transporter Type 5
From the lumen to enterocyte: glucose and galactose uptake
-Move against their concentration gradient
-SGLT=Sodium Glucose Transporter
-Secondary active transport → Driving Force is sodium concentration gradient
-Sodium moves down its concentration gradient into the cell, taking a Glucose or Galactose molecule with it
-Mechanism:
-Na+/K+ ATPase on the basal membrane → pump 3Na+ outand2K+ in+utilizinganATP→↓Na+ → Na+ in lumen»_space; Na+ in the enterocyte → Glu and Gal follow Na+ from lumen to enterocyte
Absorption from enterocyte into the 🩸
-Basolateral Membrane
-GLUT-2
Not specific →Transports all monosaccharides from the basolateral membrane of enterocytes into the blood
Absorption in the liver
-Hepatic portal vein which is formed by
-Superior mesenteric vein
-Inferior mesenteric vein
-Gastric vein
-Splenic Vein
-Pancreatic vein
-Hepatic portal vein takes Glucose, Fructose, Galactose into the liver
-Use in metabolic activities
-Glycogenesis
-Glycolysis
