Digestion Lecture

Question 1

Cell types in the small intestine

enterocytes

Answer 1

respon. for digestion, absorption, secretion

turnover rate 3-6 days

susceptible to irradiation and chemotherapy

Question 2

Cell types in the small intestine

goblet cells

Answer 2

mucous secreting

produce physical, chemical and immunological barrier

Question 3

Cell types in the small intestine

patneth cells

Answer 3

part of defense, secrete agents that destroy bacteria

Question 4

forms of enterocyte membrane control

Answer 4

pinocytosis (at base of microvilli)
passive diffusion
active diffusion
facilitated diffusion

Question 5

transporters on the apical membrane of the enterocyte designed for taking in monosaccharides via _____transport

Answer 5

SGLT 1 is a Glucose-Na cotransporter, Galactose-Na cotransporter; uses secondary transport (duh)

GLUT2 is a fructose transporter

Question 6

transporters on the basolateral membrane of the enterocyte designed for taking in monosaccharides via _____transport

Answer 6

Glut2, it takes in everything (glucose, galactose, fructose)

Question 7

where is lactase located

Answer 7

on the brush boarder. deficiency causes osmotic diarrhea

undigested lactose is fermented into methane and hydrogen gas, causing excess flatulence

Question 8

Stomach: protein digesting enzymes

“endopeptidases”

Answer 8

pepsin, typsin, chymotrypsin, elastase

“endopeptidases”

degrade peptides from interior peptide bonds

Question 9

Stomach: protein digesting enzymes

“exopeptidases”

Answer 9

carboxypeptidase A
carboxypeptidase B

degrade peptides beginning at C terminus

Question 10

Trypsinogen

Answer 10

converted to trypsin by ENTEROpeptidase

trypsin converts the ENDOpeptidases into their active form

Question 11

what are the inactive/active form of the endopeptidases?

Answer 11

trypsinogen—> trypsin
chymotrypsinogen –> chymotrypsin
Proelastase —> elastase
Pro-carboxypeptidase A and B –> A and B carboxypeptidase

Question 12

where are proteases actives?

Answer 12

in the stomach AND the SI

Question 13

autocatalysis

Answer 13

trypsin’s conversion of trypsinogen into trypsin

pancreatic enzymes digest one another

Question 14

Protein in the stomach is digested to ___ by ____

Answer 14

amino acids and oligopeptides by pepsin

Question 15

protein in the small intestines is digested to ______ by ______

Answer 15

amino acids, dipeptides, tripeptides, oligopeptides

oligopeptides are further degraded by peptidase on the brush border to amino acids, dipeptides and tripeptides

Question 16

Amino acid transporters in the small intestine in the apical membrane

Answer 16

secondary a.a.-Na cotransporter

there are four: one for acidic a.a., neutral a.a., imino a.a.s, basic a.a’s

dipeptides/tripeptides have an H-Di/Tri cotransporter as well

Question 17

Amino acid transporters in the small intestine in the basolateral surface

Answer 17

four transporters for each group of amino acids using facilitated diffusion

internally there’s a peptidase to degrade dipeptides and tripeptides to a.a.s

dipeptides and tripeptides can diffuse out of the cell

Question 18

pancreatic preteases

Answer 18

trypsin, chymotrypsin, elastase, caeboxypeptidase A and carboxypeptidase B

Question 19

after degrading proteins, what happens to pancreatic enzymes?

Answer 19

they degrade one another and are reabsorbed

Question 20

cystinuria

Answer 20

defect or absence of Na-amino acid cotransporters

transporter for di-basic amino acids (cystine, lysine, arginine, and ornithine) are absent from small intestine and kidney

genetic disorder

amino acids are secreted into feces

Question 21

Hartnup Disease

Answer 21

Cannot absorb neutral amino acids e.g. tryptophan

recessive genetic disorder

symptoms resemble those cause by pellagra
deficiency of niacin)

symptoms: diarrhea, mood changes, neurologic problems, 
res scaly skin
photosensitivity 
short stature 
uncoordinated movements 

urine has high concentration of neutral amino acids

Question 22

Cystic fibrosis transporter mutations

Answer 22

associated with deficiency of amino acid transporters
CFTR transporter in the apical region of duct cells in pancreas

CFTR secretes chlorine, which moves back into the cell down a gradient, and pushing HCO3 into the duct lumen

CFTR mutations decrease bicarbonate secretion

pH elevation prevents activated trypsin from catalyzing the trypsinogen to trypsin conversion

ability to flush active enzymes from the duct may be lost

result– acute or recurrent peancreatits

Question 23

Where are lipids digested?

Answer 23

in the stomach and small intestine

Question 24

Triglycerides are digested via 3 enzymes

Answer 24

lingual lipase, gastric and prancreatic lipase

Question 25

cholesterol esters are degrade by one important enzyme

Answer 25

cholesterol esterase hydrolase

Question 26

phospholipids are degraded by

Answer 26

phospholipase A2

phospholipid —> lysolecithin-FA

Question 27

what must occur initially for lipid digestion

Answer 27

solubilized, formed into micelles by bile and transported to the apical region of the enterocytes

Question 28

pancreatic lipase

Answer 28

cholesterol ester hydrolase, phospholipase A2, and pancreatic lipase