Protein: Digestion And Absorption Flashcards
In gastric digestion of protein, what is the name of the protease that begins cleaving off bonds in peptides?
Pepsin
What are the 2 types of proteases?
Endopeptidase and exopeptidases
What are the 2 zymogens secreted in the gastric phase of protein digestion?
HCl and pepsinogen
Which bonds are cleaved by endopeptidases?
Those not next to the N and C terminus
Exopeptidases cleave bonds where in the peptide?
Next to the N and C terminus
HCl is secreted by which cells?
Parietal
Pepsinogen is the inactive form of what enzyme?
Pepsin
What activates pepsin?
HCl or itself
What does the pancreas secrete
Enzymes for digestion and sodium bicarbonate
What is the function of sodium bicarbonate?
To neutralize chyme in the duodenum
The pancreas is stimulated to secrete zymogens by what molecule ?
CCK from the duodenum
What are the 3 zymogens secreted by the pancreas?
Trypsinogen, chymotrypsinogen, and procarboxypeptidase
How are zymogens activated?
The brush border of the git secretes endopeptidases such as entrokinase which activate trypsinogen into trypsin which in turn activates the other zymogens and itself
Where is protein absorbed?
Duodenum and jejunum
Where is protein absorbed to?
Into the bloodstream or into the enterocyte itself
Absorption is driven by what?
Gradients
How are amino acids absorbed?
The sodium/potassium pump creates a gradient inside the enterocyte. When sodium comes into the cell, it brings in an AA through an AA carrier
How are peptides absorbed?
The enterocyte creates a proton gradient by pumping sodium in and protons out. The peptide carrier brings in a peptide and protons. The peptide is then hydrolyzed inside the enterocyte into an AA
How are AA transported in the blood ?
As a free amino acid
Where do the AA go?
Into portal blood, then to liver, then to tissues
What is the first tissue that uses AA?
The enterocyte itself
How can intact proteins be absorbed?
Through tight junctions of enterocyte or through endocytosis
What is closure in neonates?
When the small intestine loses the ability to absorb intact proteins, such as Immunoglobulins, for passive immunity
Which cells secrete pepsinogen?
Chief cells
