Stomach Secretions:
· HCL –Hydrochloric Acid. Enough of this is added to bring the stomach contents to a ph of 1.5-2.0,
                              making this the most acid area in your body. This acid has 3 important roles:
o It kills most of the microorganisms ingested with our food
o It denatures proteins, making them easier to digest
o It aids in the formation of Pepsin and provides the acid environment in which Pepsin works most efficiently
                                   (Pepsin does not well at a ph above 2.4)
· Pepsin: a protein-digesting enzyme. (only cleaves peptide bonds involving phenyalanine or tryrosine)

Bile:
· Bilirubin—a waste pigment from the heme portion of hemoglobin (4 heme subunits/hemoglobin molecule). The liver recycles the iron and amino acids from the hemoglobin of old dead erythrocytes (RBCs), but the bilirubin is discarded in the bile. Bilirubin is indirectly responsible (altered by bacterial action) for the brownish color of our feces—without it they would be cream colored.
· Excess Cholesterol—Cholesterol is a nutrient, but one your body can make for itself (used in making some hormones, etc.) When more comes in through the diet than is needed, the liver can remove some of it and excrete it in the bile. Too bad it can’t remove all the excess cholesterol, as we often intake a substantial excess of this lipid.
· Bile Salts—which physically breakup (disperse—emulsify) large lipid droplets into millions of microscopic droplets. This is done to increase the surface area of the lipids for more efficient digestion by lipases.

Pancreas Secretions:
· Bicarbonate ions (HCO3)—these are basic and neutralize the acid stomach contents as they move into the small intestines. Enough is added to bring the ph to about 8, just slightly basic. The enzymes added in the small intestines work very well at this ph, but they would not work well in a more acid environment.
· Amylase—the same enzyme as was found in saliva. It continues the same job here, working on starch and
                        cleaving off maltose units.
· Lipases—to digest the lipids ( fats, oils, waxes, etc. )
· Nucleases—to digest the DNA, RNA, etc. into nucleotides.
· More Protein-digesting enzymes to split peptide bonds that were not split by Pepsin, back in the stomach. They include:
                           o Trypsin (breaks only bonds involving lysine or arginine)
                           o Chymotrypsin
                           o Carboxypeptidase

                                                           Ser—Ile—His—Pro—Arg—Pro—Ser—Val—Tyr—Ala—Met