Digestion and Absorption of Shit

Question 1

Carbohydrate Absorption

Answer 1

Glucose and Galactose are absorbed via co-transport w/ Na+ and then cross to blood via GLUT 2
-Na+ gradient maintained by Na+/K+ on basolateral side

*Fructose undergoes facilitated diffusion on both sides via GLUT 5 and GLUT 2

Question 2

Lactose intolerance

Answer 2

Lactase deficiency causing lactose to remain in GI tract w/ water
=>diarrhea, borborygmi, gas

*Undigested lactose metabolized by bacteria

Question 3

Protein Digestion

Answer 3

Enterokinase activates trypsinogen, chymotrypsinogen, and proelastase

=> Hydrolyze interior peptide bonds to di and tripeptides

Question 4

Peptide Absorption

Answer 4

Di and Tri-peptides use H+-dependent PEPT1 and are hydrolyzed to AAs in the enterocyte

-Reach blood via facilitated diffusion

Question 5

Hartnup disease

Answer 5

Affects uptake of neutral AAs

Question 6

Cystinuria

Answer 6

Affects uptake of basic AAs

Question 7

Iron absorption

Answer 7

Gastric acid dissolves ferric iron and complexes it w/ Vit C

-Uses Dcytb to become ferrous iron

=>Crosses into enterocyte via DMT1 and gets stored as ferritin

Question 8

Iron mobilization

Answer 8

Ferritin gets transported out of enterocyte via ferroportin and is converted to Fe3+

-Binds to transferrin and lives happily ever after

Question 9

Hepcidin

Answer 9

Liver released enzyme that binds to ferroportin when plasma [Fe3+] is high

-Iron cannot be sent into blood and is lost when enterocyte dies

Question 10

Hemochromatosis

Answer 10

Defect in HFE gene causes drop in hepcidin levels

=>Excess iron collects in liver, pancreas, arteries

Question 11

Na+ absorption

Answer 11

Duodenum/Jejunum= Na+/glucose, AA, or H+

ileum= Na+/Cl-

Colon= Facilitated diffusion

Question 12

Cl- absorption

Answer 12

Paracellular and HCO3- exchange

Question 13

Carbohydrate Digestion

Answer 13

Converted to maltose, maltotriose, and dextrin by a-amylases

-Later hydrolyzed to glucose by brush-border enzymes