Digestion help, please

Published Jan 14, 2003

139 Posts

can someone please check my work and tell me if i have sufficiently described the process of digestion of a polsaccharide molecule? i've done all of the work, but i am unsure if it is complete since i've stared at it since 9am this morning and might be missing something that i am unaware of. the first paragraph (blue)is the essay assignment, the following paragraphs is my answer. if anyone can give any opinions, tips, suggestions, i would really be thankful and grateful. i want to do well on this, as this is our first test grade. thanks in advance.

1.digest a carbohydrate molecule through the gastrointestinal tract. assume that this molecule is a polysaccharide. be sure to include organs involved, hormones and enzymes. after digestion is complete - how and where is this molecule absorbed.

initial hydrolosis of starch begins in the mouth as salivary amylase (ptyalin) begins to break the food down as it is chewed. mucus helps form a bolus to aid in swallowing. the bolus moves to the back of the throat at the pharynx, travels through the epiglottis and down the esophagus, and into the stomach.

once it reaches the stomach, hydrochloric acid is released by the parietal cells on the wall of the stomach and the salivary amylase becomes inactive. the food mixes with the gastric juices of the stomach via the wave-like contractions of the stomach. gastric juices are made up from hydrochloric acid, protease, gastric lipase, mucus, intrinsic factor, and gastrin. gastrin is a hormone secreted from the anrtral mucosa of the stomach that stimulates gastric secretions and motility. at this time, the food and gastric juice mixture is called chyme, and is 50% water, semi liquid solution. the chyme then moves into the duodenum.

the presence of chyme stimulates the release of secretin.secretin is a hormone which is released from the duodenal walls into the bloodstream, and stimulates the pancreas to release water and bicarbonate to neutralize the chyme. pancreatic amylase is released from the pancreas to break down the polysaccharide molecule into disaccharide and oligosaccharide molecules. enzymes from the brush border (microvilli) such as maltase, lactase, and sucrase and isomaltase break them down into monosaccharides of glucose, galactose, fructose, lactose and isomaltose.

these monosaccharides then pass through the mucosal cell, and into the bloodstream via the capillary of the villus. the portal vein carries them to the liver. glucose and galactose are absorbed by active transport, primarily by a carrier that is sodium dependant. fructose uses facilitated diffusion, a slower mode of transport, and is also sodium dependant