GI9 Digestion and absorption of proteins and vitamins Flashcards
Enteropeptidase (also called enterokinase) is secreted by the ___1____ and converts ___2___ to active ___3___. This then results in the activation of other ____4____ that are secreted in pancreatic juice.
duodenal mucosa
2) trypsinogen
3) trypsin
4) pro-enzymes
what forms trypsin?
Enteropeptidase (also called enterokinase
1) What enzymes work on interior bonds of polypeptides?
2) which ones act on carboxyl and amino ends of the protein structure?
3) What are 2s are type of?
1) Trypsin, chymotrypsin and elastase and endo peptidases
2) carboxypeptidase a and b
3) exopeptidases
About ?A?% of ingested protein is digested and absorbed in the duodenum. The pancreatic proteases convert protein to peptides and ___B___
50%
b= oligopeptides
1) How many transport systems are there for proteins?
2) How many are active?
3) How many are passive
4) Why does glutamine not have a transporter?
1) 5
2) 2
3) 3
4) it is non-essential, we can synthesise it ourselves
1) What are the small polypeptides that can enter the intestinal epithelial cells?
2) What happens to them in the cytosol
3) How do the leave, what transporters are on the basolateral membrane?
4) How do they enter the intestinal epithelial cells ?
1) aminoacids, dipeptides, tripeptides, tetrapeptides
2) cystolic peptidases break the peptides down into amino acids
3) enter the blood via 1 of 5 protein transport system (2 active & 3 passive)
4) 1 of 7 specific transporters on the brush border membrane , 5 depend on sogium gradient and are active, 2 involve facilitated transport
How are fat soluble vitamins absorbed?
depend of the presence of dietary fat, and diffuse across brush border membrane
Where does most vitamin absorbtion occur
upper small intestine
How is vitamin B12 absorbed?
1) bound to proteins , released when protein broken down and bind to R-protein in stomach, and bind with a lower affinitiy to intrinsic factor
2) in duodenum, Pancreatic proteases degrade B12 -R-protein complexes
3) • B12 now binds with intrinsic factor (IF) and these complexes resist digestion by proteases
4) brush border membrane of the ileum has receptors for IF- B12 complexes
4) • Little is known of what happens in intestinal epithelial cell but there is a ~4 hour delay before B12 enters blood
5) • In blood it is bound to a carrier called transcobalamine II
What secretes intrinsic factor?
gastric parietal cells and is a glycoprotein.
How can pancreatic insufficiency lead to B12 deficiency?
R-proteins are not degraded so remain attached and don’t form IF- B12 complexes.
