The semantics of this question made me vomit blood.

One day a patient will look me in the eyes and ask, "Where are tripetides broken down?" I will smile at them and say, "the intestinal mucosa and not the duodenum." They'll smile back and I'll walk away and think of this moment as I jump from the window.

The duodenal lumen (and pancreatic proteases like CHYMOTRYPSIN) is the site where pancreatic enzymes (“endopeptidases”) cleave large polypeptides into smaller bits (=dipeptides,tripeptides). It is at the BRUSH BORDER where the smallest kinds of peptides (dipeptides,tripeptides) are broken down into their amino acids, which finally can be co-transported with Na+ into the intestinal cell.

I think about it this way:

• stomach acid denatures and “opens up” proteins (without specific cleavage);
• pancreatic enzymes then cleave denatured polypeptides into smaller bits;
• brush border enzymes finally break down tiniest peptides into absorbable amino acids.

The semantics of this question made me vomit blood.

At least one day a patient will look me in the eyes and ask " where are tripetides broken down at". I will smile at them and say "the intestinal mucosa and not the duodenum". They'll smile back and then i'll then i'll walk away and think of this moment as I jump from the window.

Why is duodenal lumen incorrect? I thought pancreatic enzymes (chymotrypsin, carboxypeptidase) would be located here.