The parts of the digestive system and their functions are listed below: Mouth - physical digestion of food using teeth and taste of food to detect toxins etc. Salivary Glands - produces saliva when the body thinks it is, or is, getting food. The saliva has enzymes and helps to break down the food Pharynx - just a passage really and also where the food is sent into the correct passageway Esophagus - the tube that carries the food bollus from the pharynx to the stomach using peristalsis Stomach - physical mixing of food, chemical digestion of proteins into oligopeptides, abosorption of some alcohol, mechanical digestion:
Proteins The digestion of protein entails breaking the complex molecule first into peptides, each having a number of amino acidsand second into individual amino acids. The pepsins are enzymes secreted by the stomach in the presence of acid that breaks down proteins proteolysis.
The pepsins account for about 10 to 15 percent of protein digestion. They are most active in the first hour of digestion, and their ability to break down protein is restricted by the necessity for an acidic environment with a pH between 1.
The trypsins proteolytic enzymes secreted by the pancreas are much more powerful than pepsins, so the greater part of protein digestion occurs in the duodenum and upper jejunum.
Therefore, even after total removal of the stomach, protein digestion usually is not impaired.
Pancreatic secretion contains inactive protease precursors that become enzymatically active after interacting with another enzyme, enterokinasewhich is secreted from the microvillous component of the enterocytes in the duodenal and jejunal mucosa.
Trypsinogen is activated in the intestine by enterokinase, which is liberated from duodenal lining cells by the interaction of bile acids and CCK. This activation of trypsinogen to trypsin is initiated by the cleavage from it of six terminal amino acid residues.
The other proteases are activated by free trypsin.
The net effect of these proteases is to reduce dietary proteins to small polypeptide chains of two to six amino acids and to single amino acids. Trypsin activates the other pancreatic proteases, including chymotrypsin and elastase.
Trypsin, chymotrypsin, and elastase are known as endopeptidases and are responsible for the initial breakdown of the protein chains to peptides by hydrolysis. The next step, the breakdown of these peptides to smaller molecules and then to individual amino acids, is brought about by the enzymic activity of carboxypeptidases, which are also secreted by the pancreas.
Peptidase activity commences outside the enterocytes in the mucus and brush border and continues inside the cell. A different peptidase appears to be involved in each stage of the breakdown of protein to amino acids. Likewise, the transport of different peptides involves different mechanisms.
Dipeptides peptides that release two amino acids on hydrolysis and tripeptides peptides that release three amino acids are moved from the surface brush border into the cell by an energy-requiring process involving a carrier protein. Small peptides with few amino acids are absorbed directly as such.
The greater part of the breakdown of peptides to amino acids takes place within the enterocyte. Curiously, small peptides are absorbed more rapidly than amino acids, and, indeed, the precise details of the mechanism for absorption of amino acids are largely unknown.
It is known that some amino acids have a specific individual transport system while others share one. Amino acids may be classified into groups, depending upon their optical rotatory characteristics i.
Levorotatory amino acids are absorbed extremely rapidly—much more rapidly than are dextrorotatory amino acids.
In fact, levorotatory amino acids are absorbed almost as quickly as they are released from protein or peptide. Neutral amino acids have certain structural requirements for active transport, and if these specific structural arrangements are disturbed, active transport will not occur.
Basic amino acids, which have a pH above 7, are transported at about 5 to 10 percent of the rate of neutral levorotatory amino acids.The digestive system is a group of organs working together to break down food into tiny molecules.
Digestion of food is important so that we can obtain energy from our food. The human digestive system is a series of organs that converts food into essential nutrients that are absorbed into the body and eliminates unused waste material.
It is essential to good health. Digestive system is the food processing system of human body. The whole digestive system is in the form of a long, hollow, twisted and turned tube, called the alimentary canal, which starts from the oral cavity and ends at the anus.
Mitochondria - Turning on the Powerhouse Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system which takes in nutrients, breaks them down, and creates energy rich molecules for the cell.
The biochemical processes of the cell are known as cellular iridis-photo-restoration.com of the reactions involved in cellular respiration happen in the mitochondria.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder).Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.
The process of digestion has many stages. The first stage is the cephalic phase of. 1 Biology Human Digestive System Anatomy Objectives: 1.
Learn the anatomy of the digestive system. You should be able to find all terms in.