Chpt 44 Animal Nutrition Animals have two basic requirements 1 Chemical energy from ATP 2 Carbon containing molecules Animals are heterotrophs They obtain the energy and nutrients they need from other organisms Of the 20 amino acids 12 can be made The remaining are called essential amino acids because they cannot be synthesized by humans and hence must be obtained from food Essential amino acids EAAs Essential fatty acids EFAs cannot be synthesized by humans and must be obtained from food There are nine EAAs and 2 EFAs Vitamins are organic compounds that are vital for health but are required only in minute amounts several function as coenzymes in critical reactions Electrolytes are inorganic ions that influence osmotic balance and are required for normal membrane function Minerals are inorganic substances that fulfill a variety of functions not performed by electrolytes Often they are important components of cofactors or structural materials Digestion takes place in the digestive tract also called the alimentary canal or gastrointestinal GI tract Digestive tracts come in two general designs 1 Incomplete digestive tracts 2 Complete digestive tracts two openings they start at the mouth and end at the anus Complete digestive tracts have three advantages 1 Animals can feed on large pieces of food 2 Chemical and physical processes can be separated within the canal so that they occur independently of each other and in a prescribed sequence 3 Material can be ingested and digested continuously The flow of the food is in one direction Churning mixes the food with gastric juice which contains hydrochloric acid HCl and the enzyme pepsin to begin the digestion of proteins Specialized stomach cells called chief cells contain a pepsin precursor called pepsinogen that is converted to pepsin in the presence of the HCl Secretion of a protease in inactive form prevents destruction of proteins in the synthesizing cells Ruminants have a complex four chambered stomach specialized for digesting cellulose rather than protein The largest chamber of the ruminant stomach is the rumen Ruminants are able to harvest energy from cellulose thanks to a combination of specialized anatomical structures and symbiotic relationships with bacteria and unicellular protists These organisms have enzymes capable of digesting cellulose and yielding glucose This is an anaerobic process yielding fatty acids which become the main energy source HCL denatured protein Pepsin breaks down the peptide bonds between amino acids of proteins in the stomach Small Intestine duodenum Main site of nutrient digestion absorption Pancreatic enzymes are released into small intestine via the pancreatic duct Enzymes from the pancreas in the small intestine called proteases further digest polypeptides to monomers There are many types of proteases each specific for a different kind of polypeptide Proteases are synthesized in inactive form by the pancreas transferred through the pancreatic duct to the small intestine and activated there Pancreatic enzymes are activated by another enzyme known as enterokinase What Regulates the Release of Pancreatic Enzymes A second hormone cholecystokinin stimulates enzyme secretion from the liver and gall bladder which aid in lipid digestion Gastrin is a hormone found in the stomach gastrin stimulates the secretion of the HCl The pancreas also produces enzymes for the digestion of DNA RNA and carbohydrates Nucleases digest the RNA and DNA Pancreatic amylase continues the digestion of carbohydrates Pancreatic lipase breaks certain bonds present in complex fats Results in the release of fatty acids and other small lipids Hydrophobic fats tend to enter the small intestine in large globules that must be broken up emulsified before digestion can begin Emulsification results from the action of small lipids bile salts synthesized in the liver and secreted in a complex solution called bile Bile is stored in the gallbladder When bile enters the small intestine it raises the pH and emulsifies the fat into small globules Large Intestine Colon H2O Absorption Site for Vitamin K synthesis When solutes from digested material are brought into the epithelium of the small intestine via active transport water follows passively by osmosis Feces held in rectum until eliminated via defecation BacT residing in Colon produce vitamin K Vit K assists with blood clotting Individuals on Coumadin warfarin medication to prevent formation of blood clots eg the cause of stroke need to keep their vitamin K status at a constant level and not ingest too much Antibiotics the kill off bacteria also lower the bacT in our gut microflora which can compromise Vit K status as well and in otherwise healthy people this could compromise the ability to clot blood especially if not ingesting ample green leafy veggies The Large Intestine Cecum and Appendix Cecum outpocketing of the digestive tract located at the beginning of the large intestine is chamber for processing cellulose Appendix is a residual organ that plays a small role in immune function 1 Nutritional Homeostasis Glucose as a Case Study People with the disease diabetes mellitus experience abnormally high levels of glucose in their blood Insulin is a hormone that is produced in the pancreas when blood glucose levels are high Cells exposed to insulin increase their rate of glucose uptake and processing which consequently decreases blood glucose levels Diabetes develops in people who do not synthesize insulin type I diabetes mellitus OR Have defective versions of the insulin receptor type II diabetes mellitus Currently type 1 diabetes mellitus is treated with insulin injections and careful attention to diet Type 2 diabetes is managed through i Prescribed diets ii Monitoring blood glucose levels iii Drugs that increase cellular responsiveness to insulin Although some individuals have a genetic predisposition for type 2 diabetes there is strong evidence that environmental or lifestyle conditions such as increased fat and overall caloric intakes and decreased physical activity have an important impact Body mass index BMI is often used to determine obesity www eatright org Academy of Nutrition and Dietetics formerly the American Dietetic Association https fnic nal usda gov professional and career resources dietetic associations Center for Science in the Public Interest http www cspinet org Chpt 46 Animal Nervous Systems Complex processes such as moving seeing and thinking are based on seemingly simple