Digestive & Metabolism Worksheet

Betty Braziel

Anatomy & Physiology

May 4, 2013

Extra Credit

Digestive & Metabolism Worksheet

1)        Upon consumption of the ham and cheese sandwich, it follows the pathway to the stomach where the food is churned vigorously by muscular contractions of the three muscle layers if the stomach wall.  In the lumen of the stomach, secretion of large amounts of hydrochloric acid and an enzyme, pepsin.  HCI helps break down cell membrane and cause large molecules to uncoil, exposing their bonds to enzyme action.  

The starch from the bread and protein from the cheese appear coiled-shaped, and in tight globular shapes once consumed. Later to be stretched out and lengthened. The HCI provides a greatly acidic environment to allow pepsin into polypeptides of shorter length.  It finds a specific amino acid in the cheese protein and breaks the bond between itself and the adjacent amino acid.  It also breaks down most of the salivary amylase, which stops the digestion of starch.  When the stomach has finished churning and further breaking down the food, the small portion left of acidic liquid (chime) is left.

        The release of fat from the cheese and butter also arrive in the lumen. The lumen is full of watery medium, which causes the fat to clump together. Once the food has been in the stomach long enough for the pepsin to complete its job, the pyloric sphincter begins releasing materials little at a time into the duodenum. Secretions from the pancreas, liver, and gull bladder pour into the duodenum via the common bile duct. Bile secretions that are temporarily stored in gull bladders includes, amphophilic molecules called “bile salts” are slightly basic and help neutralize the stomach acid. Their main job is to breakdown the fat droplets to smaller particles, the hydrophobic ends of the salts dissolve the fat, and hydrophilic ends dissolve the surrounding water, which then disperses the fat throughout the intestinal fluid. The fat becomes tiny micro-droplets with high surface area to volume ratio, making it easier for the enzymes. Bile also includes bile pigments left over wastes from the liver breaking down hemoglobin from expired Red blood cells.

        The pancreatic fluid is rich in sodium bicarbonate (NaHCO3) which neutralizes the HCl from the stomach and making the duodenal fluid slightly basic. Pancreatic amylase picks up where salivary amylase left off, removing maltose molecules off the ends of starch. The simple chemical reaction allows the bread to digest completely to disaccharides within a half an hour after entering the stomach. Lipase breaks down the fat micro-droplets into glycerol and fatty acids, a slow process taking hours to complete. Milk fat from the cheese and butter are only digested partially. Nucleases break DNA and RNA down to their basic molecules for absorption. The pancreas releases trypsin and chymotrypsin that locate specific amino acids in the polypeptide chains, breaking them down to shorter peptides. Aminopeptidase and carboxypeptidase also take off individual amino acids from these peptides, both working from either end. When the protein in the cheese is ready to be absorbed, they dissolve individual amino acids and short chains of 2-4 amino acids.