L8 - Digestion and Absorption Flashcards
Which of the following CANNOT pass the intestinal epithelial barrier? A. Glucose B. Galactose C. Fructose D. Sucrose
D. Sucrose (dissaccharide)
Amylose
straight chain polymer of glucose
Amylopectin
branched-chain polymer of glucose
Which of the following is NOT a dissaccharide? A. Trehalose B. Sucrose C. Lactose D. Galactose
D. Galactose
B1,4-linkage
Can’t be hydrolyzed by human gut floral enzymes
Alpha-amylase will hydrolyze
A. Alpha1,6-linkage
B. Alpha1,4-linkage
C. Beta1,4-linkage
B. Alpha1,4-linkage
Straight chain parts
What is the name for the branching linkage in starch
alpha1,6-linkage
Pancreatic amylase digests a-1,4-bonds yielding a mixture of
- a-limit dextrins (oligosaccharide)
- Maltose (disaccharide)
- Maltotriose (trisaccharide)
Name 3 brush border enzymes
- a-dextrinase - digests a-limit dextrins
- maltase - digests maltose
- sucrase - digests maltotriose
What brush border enzyme can digest maltotriose AND sucrose?
Sucrase
Which of the following requires amylase digestion? A. Trehalose B. Sucrose C. Lactose D. Starch
D. Starch
Glucose + glucose =
Trehalose
Glucose + galactose =
Lactose
Glucose + fructose =
Sucrose
Which brush border enzyme can debranch alpha-1,6-linkages?
alpha-dextrinase
What’s the only transporter on the luminal side of the intestinal brush border, that utilizes Na?
SGLT1 (Na/Glc transporter 2ndary active)
Which of the following transport glucose and galactose against their concentration gradient, coupled to Na+ influx? A. GLUT 2 B. GLUT 5 C. SGLT 1 D. SGLT 2
C. SGLT 1
Which of the following are basolateral on brush border epithelial cells? A. GLUT 2 B. GLUT 5 C. SGLT 1 D. B and C
A. GLUT 2
Lactose intolerance
Defective or absent lactase. Osmotic diarrhea and dehydration result; lactose pulls water.
Which results in decreased absorption of glucose/galactose? A. Lactase deficiency B. SGLT-1 deficiency C. GLUT 5 deficiency D. A and B
D. A and B
Lactase deficiency - can’t make glucose/galactose from lactose
SGLT-1 deficiency - can’t absorb gluc/gal into brush border epithelia
Which one of these 10 aa’s are NOT essential?
Lys, His, Val, Leu, Ile, Phe, Try, Thr, Met, Pro
Pro
Which of the following is NOT an endopeptidase, but an EXOpeptidase?
A. pepsin B. Trypsin C. Chymotrypsin D. Elastase E. carboxypeptidase
E. Carboxypeptidase
hint: carboxy
“What is the key enzyme, located on the brush border, that initiates the process of digestion?”
Enterokinase (activates trypsinogen into trypsin)
Trypsin activation yields which 5 active enzymes?
- Trypsin
- Chymotrypsin
- Elastase
- Carboxypeptidase A
- Carboxypeptidase B
Amino acids co-transport with
Na+
Di- and tripeptides co-transport with
H+
In what organ does lipid digestion BEGIN?
stomach
In what organ does MOST lipid digestion occur?
Small intestine
What’s the 1st enzyme that is affected by pH imbalance?
Pancreatic lipase
Name 3 pancreatic lipolytic enzymes that work at neutral pH
Pancreatic Lipase
Phospholipase A2
Cholesterol ester hydrolase
note: this is why you get steatorrhea when the pylorus dumps chyme in too fast - acidic stomach contents deactivate these lipolytic enzymes causing fatty poopoo. Could this be a cure for obesity? ;)
What do bile acids to do pancreatic lipase?
Inactivates it
What does cofactor lipase do?
Anchors pancreatic lipase to fat droplet, even in presence of bile acid. That way bile acids can emulsify, while lipase can do its thing too.
Can micelles enter a cell?
no
Where is bile reabsorbed into enterohepatic circulation, and by what transporter?
Ileum, ASBT transporter
Note: ileal resection promotes lost bile, and steatorrhea since can’t make micelles
What’s cholestyramine?
complexes with bile so you can poop it out, and start from scratch using cholesterol.
