Sci Rep. Complex and multi-allelic copy number variation in human disease. Briefings in Functional Genomics. Low copy number of the salivary amylase gene predisposes to obesity. The physiologic and phenotypic significance of variation in human amylase gene copy number. Am J Clin Nutr. High endogenous salivary amylase activity is associated with improved glycemic homeostasis following starch ingestion in adults. J Nutr. Salivary Amylase: Digestion and Metabolic Syndrome. Current Diabetes Reports.
BMC Med. Rethinking the starch digestion hypothesis for AMY1 copy number variation in humans. Am J Phys Anthropol. Oxford University Press is a department of the University of Oxford.
It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account.
Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Salivary amylase gene variations influence the physiologic response to starchy foods: 2 sides of the story. Emily Sonestedt Emily Sonestedt. Address correspondence to ES e-mail: emily. Oxford Academic. Select Format Select format.
Permissions Icon Permissions. When carbohydrates reach the stomach no further chemical breakdown occurs because the amylase enzyme does not function in the acidic conditions of the stomach. But mechanical breakdown is ongoing—the strong peristaltic contractions of the stomach mix the carbohydrates into the more uniform mixture of chyme. The chyme is gradually expelled into the upper part of the small intestine.
Upon entry of the chyme into the small intestine, the pancreas releases pancreatic juice through a duct. This pancreatic juice contains the enzyme, pancreatic amylase, which starts again the breakdown of dextrins into shorter and shorter carbohydrate chains.
Additionally, enzymes are secreted by the intestinal cells that line the villi. These enzymes, known collectively as disaccharidase, are sucrase, maltase, and lactase. Sucrase breaks sucrose into glucose and fructose molecules. Maltase breaks the bond between the two glucose units of maltose, and lactase breaks the bond between galactose and glucose. Once carbohydrates are chemically broken down into single sugar units they are then transported into the inside of intestinal cells.
When people do not have enough of the enzyme lactase, lactose is not sufficiently broken down resulting in a condition called lactose intolerance.
The undigested lactose moves to the large intestine where bacteria are able to digest it. The bacterial digestion of lactose produces gases leading to symptoms of diarrhea, bloating, and abdominal cramps. Lactose intolerance usually occurs in adults and is associated with race. The severity of the symptoms depends on how much lactose is consumed and the degree of lactase deficiency. The cells in the small intestine have membranes that contain many transport proteins in order to get the monosaccharides and other nutrients into the blood where they can be distributed to the rest of the body.
The first organ to receive glucose, fructose, and galactose is the liver. The liver takes them up and converts galactose to glucose, breaks fructose into even smaller carbon-containing units, and either stores glucose as glycogen or exports it back to the blood. How much glucose the liver exports to the blood is under hormonal control and you will soon discover that even the glucose itself regulates its concentrations in the blood.
Glucose levels in the blood are tightly controlled, as having either too much or too little glucose in the blood can have health consequences.
Glucose regulates its levels in the blood via a process called negative feedback. An everyday example of negative feedback is in your oven because it contains a thermostat. The glucose thermostat is located within the cells of the pancreas. After eating a meal containing carbohydrates glucose levels rise in the blood.
Insulin-secreting cells in the pancreas sense the increase in blood glucose and release the hormone, insulin, into the blood.
In the case of muscle tissue and the liver, insulin sends the biological message to store glucose away as glycogen. The presence of insulin in the blood signifies to the body that glucose is available for fuel.
As glucose is transported into the cells around the body, the blood glucose levels decrease. Insulin has an opposing hormone called glucagon. Glucagon-secreting cells in the pancreas sense the drop in glucose and, in response, release glucagon into the blood. All living beings need energy to survive. It is from the food we consume that we get our energy. We know that the energy we are getting is by the process of digestion that breaks down the complex substance of starch into simpler molecules of glucose, which are further metabolized into CO2 and water through the process of glycolysis.
The human digestive tract starts at the mouth and ends at the anus. The digestion of the food starts as soon as we put food in our mouth. Our teeth cut the food into small pieces and the salivary glands secrete saliva that mixes with these food materials. The saliva contains an enzyme called salivary amylase which hydrolyses starch into maltose. The complete digestion of starch occurs only in the small intestine by the action of pancreatic amylase.
All enzymes are proteinaceous in nature.
0コメント