Our teeth break food down into small pieces when we chew. This is only a start to the process of digestion, as chewed pieces of food are still too large to be absorbed by the body. Food has to be broken down chemically into really small particles before it can be absorbed. Enzymes are the biological catalysts needed to make this happen quickly enough to be useful.
Enzymes are not living things. They are just special proteins that can break large molecules into small molecules. It is not foolproof though because some micro-organisms that cause food-poisoning are adapted to be able to survive in the stomach acids. The acid can sometimes cause stomach ulcers if the protective layer on the inside of the stomach wall is damaged. Bile is produced in the liver and stored in the gall bladder.
As food leaves the stomach, bile is squirted along the bile duct and into the duodenum. It is extremely important as it helps to neutralise the acidic contents of the stomach as they enter the top of the small intestine.
This prevents the acid from damaging the small intestine which is kept at a pH of about 7. This is the optimum pH for the carbohydrases, proteases and lipases made in the pancreas and in the small intestine itself to work. Alkaline bile raises the pH of the acidic stomach contents when they come into the small intestine. Chemical digestion.
Different organs play specific roles in the digestive process. The animal diet needs carbohydrates, protein, and fat, as well as vitamins and inorganic components for nutritional balance.
How each of these components is digested is discussed in the following sections. The digestion of carbohydrates begins in the mouth. The salivary enzyme amylase begins the breakdown of food starches into maltose, a disaccharide. As the bolus of food travels through the esophagus to the stomach, no significant digestion of carbohydrates takes place.
The esophagus produces no digestive enzymes but does produce mucous for lubrication. The acidic environment in the stomach stops the action of the amylase enzyme. The next step of carbohydrate digestion takes place in the duodenum. Recall that the chyme from the stomach enters the duodenum and mixes with the digestive secretion from the pancreas, liver, and gallbladder.
Pancreatic juices also contain amylase, which continues the breakdown of starch and glycogen into maltose, a disaccharide. The disaccharides are broken down into monosaccharides by enzymes called maltases. Maltase breaks down maltose into glucose. Other disaccharides, such as sucrose and lactose are broken down by sucrase and lactase, respectively. The monosaccharides glucose thus produced are absorbed and then can be used in metabolic pathways to harness energy.
The monosaccharides are transported across the intestinal epithelium into the bloodstream to be transported to the different cells in the body. The steps in carbohydrate digestion are summarized in Figure A large part of protein digestion takes place in the stomach. The enzyme pepsin plays an important role in the digestion of proteins by breaking down the intact protein to peptides, which are short chains of four to nine amino acids.
In the duodenum, other enzymes— trypsin, elastase , and chymotrypsin —act on the peptides reducing them to smaller peptides. Trypsin elastase, carboxypeptidase, and chymotrypsin are produced by the pancreas and released into the duodenum where they act on the chyme. Further breakdown of peptides to single amino acids is aided by enzymes called peptidases those that break down peptides.
Specifically, carboxypeptidase, dipeptidase , and aminopeptidase play important roles in reducing the peptides to free amino acids. The amino acids are absorbed into the bloodstream through the small intestines.
The steps in protein digestion are summarized in Figure Lipid digestion begins in the stomach with the aid of lingual lipase and gastric lipase. However, the bulk of lipid digestion occurs in the small intestine due to pancreatic lipase. When chyme enters the duodenum, the hormonal responses trigger the release of bile, which is produced in the liver and stored in the gallbladder.
This gives each protein its own individual properties. Protease enzymes are responsible for breaking down proteins in our food into amino acids. Then different enzymes join amino acids together to form new proteins needed by the body for growth and repair.
Protease enzymes are produced in your stomach, pancreas and small intestine. Lipids are fats and oils. Lipids are large molecules made from smaller units of fatty acids and glycerol.
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