POOR WAND’RING BUN
by Arthur W. Siebens, Ph.D., Copyright 2002
to the tune of “Poor Wand’ring One,” from The Pirates of Penzance by Sir William Gilbert and Sir Arthur Sullivan
Poor burger bun
Cov’ring the burger I ate
We’ll explore your fate
Into glucose you’ll break
Poor burger bun!
Poor wandering bun
As you go through the digestive (alimentary, gastrointestinal, GI) tract
The burger is cracked
Into monomers lacked
The mouth is where you’re first attacked.
Teeth break up, saliva lubricates
Amylose (starch in the bun) is (partly) hydrolyzed by (salivary) amylase
A food bolus by peristalsis
Moves through the esophagus
Then in the stomach, it turns into chyme (vomit).
There gastrin causes pepsin (as pepsinogen) and HCl secretion
Protein’s partly digested, then to the (small) intestine for completion
Chyme in the duodenum causes hormone secretion
That calls pancreatic enzymes.

Lipids (triglycerides/triacylglycerols) break to fatty acids through (the action of ) lipase
Proteins break to amino acids through protease(s) (e.g. trypsin, chymotrypsin, carboxypepdidases)
Nucleic acids break to nucleotides through nuclease(s) (e.g., ribonuclease, deoxyribonuclease)
Starch (amylose) breaks to glucose through (pancreatic) amylase.
Poor wandering bun
Like the burger you’ll break all the way
As the pancreas adds base (NaHCO3)
Enzymes hydrolyze with haste
What they can’t chop moves on as waste (e.g., cellulose/“dietary fiber”).

Chyme in the duodenum causes
Secretin and cholecystokinin (CCK)
To call pancreatic base and enzymes in
The gallbladder squirts in bile (made in the liver) to emulsify fat to droplets fine.
Now monomers* in the intestinal coils get
Absorbed so the nutrients don’t go down the toilet
Then water’s reabsorbed (following Na) in the large intestine.
With most water gone, just feces remain
To eliminate with minimal strain
Energy supplied by glucose derived from that poor wandering bun!
*Digestion to monomers is completed by membrane-bound enzymes in the intestinal mucosa such as dipeptidases, sucrase, lactase, lipase and nucleases.