Glycogen is a multi-branched starch with linkages at the and position. This creates very large granules of multi-branched starch. Both the parotid and pancreatic amylases hydrolyse the link, but not the terminal links or the links. This breaks amylose down into mainly disaccharides, and glycogen with its linkages into polysaccharides. The net result of these actions are numerous disaccharides and polysaccharides.
Enzymes attached to the enterocycytes of the small intestine break these down to monosaccharides. Hydrolysis by amylase : Both the parotid and pancreatic amylases hydrolyse the link, but not the terminal links or the links.
Proteins and polypeptides are digested by hydrolysis of the carbon—nitrogen C—N bond. The proteolytic enzymes are all secreted in an inactive form, to prevent auto-digestion, and are activated in the lumen of the gut. Activation is caused by HCl in the case of the stomach enzyme pepsinogen, and by enteropeptidase and trypsin in the case of the pancreatic enzymes.
Final digestion takes place by small intestine enzymes that are embedded in the brush border of the small intestine. The enzymes are divided into endo- and exo-peptidases. Stomach pepsin cleaves the interior bonds of the amino acids, and is particularly important for its ability to digest collagen.
This is a major constituent of the connective tissue of meat. In the absence of stomach pepsin, digestion in the small intestine proceeds with difficulty. Hydrolysis of peptide bond : Proteins and polypeptides are digested by hydrolysis of the C—N bond.
Fats are digested by lipases that hydrolyze the glycerol fatty acid bonds. Of particular importance in fat digestion and absorption are the bile salts, which emulsify the fats to allow for their solution as micelles in the chyme, and increase the surface area for the pancreatic lipases to operate.
Muscle cells may also take up the fatty acids and use them for muscular work and generating energy. As the body calls for additional energy, the adipose tissue responds by dismantling its triglycerides and dispensing glycerol and fatty acids directly into the blood. Upon receipt of these substances the energy-hungry cells break them down further into tiny fragments. These fragments go through a series of chemical reactions that yield energy, carbon dioxide, and water.
Lipoproteins are characterized by size, density, and composition. As the size of the lipoprotein increases, the density decreases. What should you know about these lipoproteins? Recall that chylomicrons are transporters of fats throughout the watery environment within the body. After about ten hours of circulating throughout the body, chylomicrons gradually release their triglycerides until all that is left of their composition is cholesterol-rich remnants.
These remnants are used as raw materials by the liver to formulate specific lipoproteins. Following is a list of the various lipoproteins and their functions:.
The classification of the major types of lipoproteins are based on their densities. Density range is shown as well as lipid red and protein blue content. More specifically, when looking at individual lipid profiles, a low amount of LDL and a high amount of HDL prevents excess buildup of cholesterol in the arteries and wards off potential health hazards.
In contrast, a low value of HDL is a telltale sign that a person is living with major risks for disease. In short, elevated LDL blood lipid profiles indicate an increased risk of heart attack, while elevated HDL blood lipid profiles indicate a reduced risk. The University of Maryland Medical Center reports that omega-3 fatty acids promote lower total cholesterol and lower triglycerides in people with high cholesterol.
It is suggested that people consume omega-3 fatty acids such as alpha-linolenic acid in their diets regularly. Polyunsaturated fatty acids are especially beneficial to consume because they both lower LDL and elevate HDL, thus contributing to healthy blood cholesterol levels.
Carbohydrates, proteins, and fats are the primary components of food. Some essential nutrients are required for cellular function but cannot be produced by the animal body. These include vitamins, minerals, some fatty acids, and some amino acids.
Food intake in more than necessary amounts is stored as glycogen in the liver and muscle cells, and in fat cells. Excess adipose storage can lead to obesity and serious health problems.
ATP is the energy currency of the cell and is obtained from the metabolic pathways. Excess carbohydrates and energy are stored as glycogen in the body. Skip to content Chapter Animal Nutrition and the Digestive System. Learning Objectives By the end of this section, you will be able to: Describe the process of digestion Detail the steps involved in digestion and absorption Define elimination Explain the role of both the small and large intestines in absorption.
Digestion and Absorption. Table Aminopeptidase Dipeptidase. Concept in Action. Figure Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum. Amylase, maltase, and lactase in the mouth digest carbohydrates. Trypsin and lipase in the stomach digest protein. Bile emulsifies lipids in the small intestine.
No food is absorbed until the small intestine. Common Problems with Elimination. Exercises Where does the majority of protein digestion take place? Answers A B Lipids add flavor to food and promote a sense of satiety or fullness. Fatty foods are sources of high energy; one gram of lipid contains nine calories. Lipids are also required in the diet to aid the absorption of lipid-soluble vitamins and for the production of lipid-soluble hormones.
Previous: Next: Share This Book Share on Twitter. Bile breaks the fat into small droplets that are easier for the lipase enzymes to work on. Bile is not an enzyme. Minerals, vitamins and water are already small enough to be absorbed by the body without being broken down, so they are not digested. Digestive enzymes cannot break down dietary fibre, which is why the body cannot absorb it.
Digestion and enzymes Our teeth break food down into small pieces when we chew. Enzymes Enzymes are not living things.
0コメント