Partially digested food entering the stomach is composed of di and tri saccharides, polypeptides, and lipids. The production of gastric fluid (juice) was introduced, along with the production of hydrochloric acid. The enzyme pepsin secreted was shown to be a protease enzyme, which is activated in an acidic medium. The acid serves a variety of purposes, to activate the enzyme, to help in the dissolution of minerals like calcium, and to aid in the killing of bacteria swallowed with the food. The action of the pepsin on the proteins was shown to speed up the hydrolysis of the polypeptides into di and tri peptides. The stomach contents are becoming the consistency of a mash (chyme) consisting of partially digested carbohydrates, partially digested proteins, and lipids.
The sphincter muscle opens and allows the food to enter the small intestines in controlled amounts.
The action of the intestinal glands and the pancreatic glands was briefly described, the major functions to be discussed.

The structure of amino acids was presented, along with how they bond to form a chain of amino acids we call a protein. The importance of proteins as enzymes, hormones, muscles, and cell membranes was listed. The hydrolysis of animal protein into amino acids by hydrolysis, then into human proteins was presented as the pathway to obtain proteins in humans.

A lab exercise designed to show how salivary amylase acts as an enzyme to aid in the digestion of polysaccharides into glucose.
Control test tubes and experimental test tubes were set up, with the data recorded in a data table. The conclusions following the testing were listed on the lab sheet, based on the results.

A review of chemical digestion in the mouth preceded the discussion involving chemical digestion in the stomach. The structural formula of amino acids was presented, along with the terms polypeptide, monopeptide, and peptide bonds. The hydrolysis of polypetpides(proteins) into usable amino acids was shown, and the enzyme from gastric juice presented.

A review of why digestion is needed was used to start the class. The chemical composition of carbohydrates was presented along with the nutrients which are carbohydrates. The structure and definition of a polysaccharide as well as a monosaccharide was sketched. The need to convert polysaccharides into monosaccharides in order for absorption into the blood stream and absorption into the cells was discussed. The hydrolysis of starch was outlined, showing the conversion into di and tri saccharides. The chemcical composition of saliva was presented, and that of the enzyme amylase. The action of amylase as a catalyst was explained, as speeding up the chemical reaction of polysaccharide into monosaccharide. The pH of the mouth was looked up, stressing that the enzyme worked best in neutral or slightly basic media.

The anatomy and physiology of the small intestine was examined using charts and photos. Chemical digestion study was initiated by examining the makeup of carbohydrates, specifically polysaccharide molecules like starch,and monosaccharides like sugar. The reason for the digestion of polysaccharides was outlined, and the molecular model of the starch and sugar examined through pictures.

The anatomy of the small intestine, and the digestive enzymes present in the intestine are discussed in terms of chemical digestion.

The chemical makeup of gastric juice was presented, and the physiological response for each one noted. The secretion of gastric juice due to the thought of food, the presence of food in the mouth, and the presence of food in the stomach was presented. The digestion of protein in the stomach was presented using the treatment done on the trapper St. Martin in the 1700's. The overproduction of gastric juice, specifically the hydrochloric acid, was shown to attribute to the formation of gastric ulcers, especially in hyperactive, type A personalities.

Discussion regarding the anatomy and physiology of the stomach. examine the muscular makeup of the stomach and how it is involved in mechanical digestion. The action of peristalsis in the esophagus directs the bolus of food toward the stomach, regardless of the subject's body position.
The chemical composition of gastric juice was listed, and the secretion by specific gastric glands noted. The effect of each of the materials in the gastric juice on the process of digestion, how the production of each is initiated and the possible unwanted results of over secretion will be our next lesson.

The anatomy and physiology of the mouth and its role in the process of digestion... This involves the teeth in mechanical digestion, the anatomy of the tongue and the role it plays in taste as well as bolus formation and swallowing. The salivary glands, their chemical makeup and how they affect both chemical digestion and swallowing, as well as the part played by the palate and the pharynx in reflex swallowing. We discussed peristalsis in the esophagus and how this moves the partially digested food toward the stomach, no matter what position the body is in.