GI transporters Drewes Flashcards
What 2 GI processes are under neural and hormonal control?
Secretion and motility
How does alcohol get through a membrane?
Simple diffusion
Why does carrier-mediated diffusion reach a plateau?
Because it is fully saturated with substrate
How many transmembrane segments to GLUTs have?
12
What does ABC transporter stand for?
ATP-Binding Cassette Transporter
Where does transport of nutrients and water primarily occur?
Jejunum
What type of transporters are abundant in the jejunum?
Apical or basolateral?
Active (secondary) transport
Apical
What type of transporters are on the basolateral side?
Carrier-mediated
*Going down gradient into blood
Where does reclamation of fluids, electrolytes and bile acids occur?
Transverse colon
Where does CO2 for carbonic anhydrase come from?
The blood by diffusion across the basolateral membrane
What does omeprazole bind to in the parietal cell that allows it to inhibit H+/K+ ATPase?
Sulphhydrl group
Transport between cells
paracellular
Tight junctions that are super tight do what to paracellular transport.
Decrease it
What happens to osmolarity when you digest protein and starch?
As you digest it and create more molecules…the osmolarity INCREASES and draws water in.
What is pumped into the lumen to make water follow?
NaCl
What two things cause water to move to the lumen?
NaCl
Breakdown of particles
What molecule activates CFTR?
cAMP produced by adenylyl cyclase
What toxin can constitutively turn on adenylyl cyclase causing diarrhea and hyperosmolar secretions?
CHOLERA!
Where are Na+/K+ ATPases?
Basolateral membrane
*3 sodium out, 2 K+ in
What does the peptide transporter carry?
Di and tri peptides ONLY!
Hartnup disorder
Apical neutral amino transporter defect
As the intestinal contents moves down the lumen, there are things that are not digested…bacteria begin to produce butyrate and proprionic acid…colonocyte cells use this for fuel! What transporter is a tumor suppressor gene?
MCT-1
*want this expressed! Decreased chance of colon cancer
P-glycoprotein is what type of transporter?
EFFLUXER! On Apical surface
What transporter plays a critical role in determining drug delivery?
EFFLUXERS
What factors regulate drug uptake?
Regulatory elements (promoter) controlling protein levels
Genetic polymorphisms affecting activity
Presence/co-administration of transporter inhibitor (drug or diet–grapefruit juice)
Why do we have taste receptors in the intestine?
To send signals to the brain that the nutrient has been ingested
