Digestion And Absorption Of Carbs

Question 1

Cellulose

Answer 1

-glucose polymer cannot be digested by mammalian
enzymes
-fiber
-helps bowel movement, metabolic process and controlling insulin release

Question 2

Dietary carbs mostly come from…

Answer 2

Starch
➡️amylose and amylopectin

Question 3

Amylopectin made up of what type of bonds

Answer 3

-α-1,4 Glycosidic Bonds
-α-1,6 Glycosidic Bonds

Question 4

Amylose made of what type of bonds

Answer 4

α-1,4 Glycosidic Bonds

Question 5

Salivary α-Amylase

Answer 5

“Ptyalin”

-Mainly secreted by extrinsic glands
-Only targets the α-1,4 glycosidic bonds and breaks down Amylopectin and Amylose

Question 6

Amylose is broken down into…

Answer 6

-maltose➡️ disaccharides

-maltitriose➡️ oligosaccharides

• α-Limit dextrins →oligosaccharides

Question 7

Digestion starts in _ and continues in GI tract all the way to _

Answer 7

Oral cavity; stomach

Oral cavity → Pharynx → esophagus → Stomach

Question 8

Salivary amylase is inactivated by…

Answer 8

Gastric acid

Question 9

Digestion of carbs in pancreas

Answer 9

-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

Question 10

Digestion of carbs in small intestine

Answer 10

-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

Question 11

Brush border enzymes of small intestine

Answer 11

-Lactase
-Maltase-glucoamylase
-Sucrase
-isomaltase

Question 12

Lactase

Answer 12

-Lactose= disaccharides = Glucose-Galactose
-lactase
➡️breaks down the bond between Glu-Gal
➡️Glu, Gal

Question 13

Maltase

Answer 13

-= Glucoamylase
-Maltase → breaks down the bond Glu-Glu
-Maltose → 2 Glu
-Maltotriose →3 Glu

Question 14

Sucrase-isomaltase

Answer 14

-Sucrase → breaks down Maltose, Maltotriose, some α- Limit dextrins and Sucrose
-Sucrose = Glucose-Fructose

Question 15

Isomaltase

Answer 15

-Targets α-1,6 Glycosidic Bonds o →
-α-Limit dextrin → Glu, Glu, …

Question 16

From the lumen to enterocyte

Answer 16

Monosaccharides’ Uptake across the Apical Membrane (From Lumen to Enterocyte)

-GLUT-5
-Fructose
-SGLT
-Glucose
-Galactose

Question 17

From the lumen to enterocyte

Answer 17

Monosaccharides’ Uptake across the Apical Membrane (From Lumen to Enterocyte)

-GLUT-5
-Fructose
-SGLT
-Glucose
-Galactose

Question 18

From the lumen to enterocyte: fructose uptake

Answer 18

-Facilitated Diffusion by GLUT-5
-GLUT-5= Glucose Transporter Type 5

Question 19

From the lumen to enterocyte: glucose and galactose uptake

Answer 19

-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&raquo_space; Na+ in the enterocyte → Glu and Gal follow Na+ from lumen to enterocyte

Question 20

Absorption from enterocyte into the 🩸

Answer 20

-Basolateral Membrane
-GLUT-2
Not specific →Transports all monosaccharides from the basolateral membrane of enterocytes into the blood

Question 21

Absorption in the liver

Answer 21

-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