GI Phys: Absorption & Large Intestine Flashcards
What sugars are produced in the breakdown of sucrose?
- Glucose
- Fructose
What sugars are produced in the breakdown of lactose?
- Glucose
- Galactase
What is trehalose?
A. Dimer of glucose and galactose B. Dimer of fructose and glucose C. Dimer of glucose D. Reduced form of glucose E. Oxidized form of glucose
C. a dimer of glucose
What glucose transporters are present in the apical membrane of small intestine epithelial cells?
- SGLT 1 (glucose & Galactose)
- GLUT 5 (Fructose)
What glucose transporters are present on the basolateral side of the small intestine epithelial cells?
-GLUT 2
What is insulin’s effect on glucose transporters in the intestinal epithelial cells? What are the implications for an individual with diabetes?
- Removes GLUT 2 from both apical and basolateral membranes
- lack of insulin in diabetic patients results in permanent glucose transporters in apical membrane, thus high rate of sugar absorption is maintained despite abnormally elevated blood glucose
What activates most carbohydrate digestion enzymes in the small intestine?
-Trypsin
What amino acid transporters are located on the apical side of the small intestine epithelial cells?
-Sodium AA/peptide symporters
What amino acid transporters are located on the basolateral side of the small intestine epithelial cells?
-Amino acid channel for facilitated diffusion
What is the advantage of absorbing di or tri peptides?
-If a transporter for an essential amino acid is defective or absent, that amino acid may still be absorbed by oligo carriers
Patients with a congenital absence of one of the
essential amino acid carriers do NOT become deficient
in that amino acid due to the fact that:
A. The amino acid is absorbed by passive diffusion
B. The amino acid can make use of other carriers
C. The amino acid is absorbed by facilitated diffusion
D. Peptides containing the amino acid are absorbed by
different carriers
E. The amino acid is an essential amino acid
D. Peptides containing the amino acid are absorbed by different carriers
What is the difference in absorption between fatty acids that are 14 to 18 carbons versus smaller chain fatty acids?
- fatty acids 14 to 18 carbons are packaged into chylomicrons and sent via lymphatic system
- Smaller fatty acids are more soluble and go directly into the blood stream and to the liver via portal vein
Small to medium chain fatty acids absorbed in the jejunum are delivered to the liver via the: A. Cystic artery B. Hepatic veins C. Hepatic artery D. Central veins E. Hepatic portal vein
E. Hepatic Portal Vein
What happens to indigestible carbs in the large intestine?
-Many are transformed into short-chain fatty acids by enzymes present in our microbiome, and are absorbed in the colon
What vitamin promotes Ca absorption?
-Vitamin D
How is calcium absorbed in the small intestine?
Transcellular:
- facilitated diffusion into cell
- pumped out via Na/Ca antiporter and H/Ca antiporter
Paracellular
-Passive diffusion
Active absorption only in the duodenum
How is iron absorbed in the small intestine?
- Fe binds transferrin, which binds to transferrin receptor on epithelial cell and endocytosed
- also absorbed as heme