Chemical and Biological Aspects of Nutrition
Chemical and Biological Aspects of Nutrition NUTR-23511-009
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This 7 page Class Notes was uploaded by Amy Turk on Wednesday April 27, 2016. The Class Notes belongs to NUTR-23511-009 at Kent State University taught by Dr. Tanya Falcone in Spring 2016. Since its upload, it has received 7 views. For similar materials see Science of Nutrition in Nutrition and Food Sciences at Kent State University.
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Date Created: 04/27/16
Chemical and Biological Aspects of Nutrition ● our bodies are in a constant state of renewal ● nutrients in the food we eat are used to renew body tissues ● these nutrients become available to the body through processes termed digestion and absorption ○ digestive disorders are common and often related to dietary intake ● every day, approx. 5% of our body weight is replaced by new tissue ○ cells die and new ones are made = apoptosis ○ substances in our blood are replaced ○ body fluids are replaced ● examples of cell renewal ○ taste cells are replaced every 7 days ○ cell lining in the intestinal tract are replaced every 1 to 3 days ○ cells in the skin are replaced every month ○ red blood cells are replaced every month ● digestion and absorption make nutrients available for use by every cell in the body ● digestion ○ mechanical and chemical process ○ ingested food is converted into substances that can be absorbed by the IR and utilized by the body ● absorption ○ process by which nutrients and other substances are transferred from the digestive system into body fluids for transport throughout the body Digestion ● the process by which food is broken down into absorbable units ● occurs 3-4 hours after meal ● liver ● gallbladder ● large intestine ● appendix ● esophagus ● stomach ● pancreas ● small intestine ● rectum ● anus ● oral cavity = 25-30 feet long muscular tube and organs ○ salivary glands = produce saliva ■ lubricates food so it can be swallowed and passed through the esophagus ■ produce enzymes that help break down starch and fats ● amylaze ● lipase ○ tongue = mastication and mixing of food with saliva ○ esophagus = transfers food to the stomach ○ stomach = secretes enzymes that break down proteins and fats ■ mixes and liquifies food ● gastrointestinal tract ○ small intestine = secretes enzymes that break down carbs, proteins, and fats ■ site of nutrient absorption ○ large intestine (colon) = site of water absorption ■ site of sodium absorption ■ site of most intestinal bacteria ○ rectum = stores waste product for elimination ○ anus = holds rectum closed ■ opens to allow elimination ● assisting organs ○ liver = produces bile that aids fat digestion ■ bile = acts like a detergent, breaking down globs of fat entering the small intestine to droplets, making the fat more accessible to the action of lipase [enzyme that breaks down fat] ○ gallbladder = stores and secretes bile that aids in fat digestion ○ bile duct = conducts bile to small intestine ○ pancreas = secretes enzymes that break down carbs, proteins, and fats ○ pancreatic duct = conducts pancreatic juices into small intestine Classifications of Nutritents ● macronutrients ○ carbohydrates ■ monosaccharides (simple sugars) ● glucose, fructose, galactose ■ disaccharides (simple sugars containing 2 sugar molecules) ● sucrose (glucose + fructose) ● lactose (glucose + galactose) ● maltose (glucose + glucose) ○ proteins ■ amino acids ■ dipeptides ■ polypeptides ○ fats ■ fatty acids ■ glycerol ● micronutrients bsorbable Forms of Nutrients ● carbs ○ absorbable form ■ monosaccharides ● glucose, fructose, and galactose ○ end product: glucose and/or glycogen ● protein ○ absorbable form ■ amino acids ● fats ○ absorbable form ■ fatty acids and glycerol ● vitamins and minerals ○ not broken down Enzymes ● complex protein substances that speed up reactions that break down food ● reusable due to unchanged by reactions in the body ● each macronutrient has its own set of enzymes ● over a hundred different enzymes participate in the digestion of macronutrients ● enzymes are manufactured by… ○ salivary glands ■ amylaze ■ lipase ○ stomach ■ HC1 ■ pepsin ○ pancreas ■ amylaze ■ lipase ■ trypsin ○ gastrointestinal tract (GI) ■ sucrase ■ lactase ■ maltase ● carbohydrates ○ amylaze ■ produced in the salivary glands and the pancreas ■ breaks down starch into smaller saccharides (molecules) ○ sucrase ■ produced in the small intestine ■ separates sucrose into glucose and fructose ○ lactase ■ produced in the small intestine ■ separates lactose into glucose and galactose ○ maltase ■ produced in the small intestine ■ separates maltase into two molecules of glucose ● proteins ○ pepsin ■ produced by the stomach ■ separates proteins into shorter chains of amino acids ○ trypsin ■ produced by the pancreas ● separates short chains of amino acids into molecules containing one, two, or three AAs ● fat ○ lipase ■ produced in the salivary glands and the pancreas ■ breaks down fat into 3 fatty acids and 1 glycerol backbone Digestion ● solid food stays in the stomach for over an hour ● liquids pass through within 20 minutes ● when stomach is done liquefying food… ○ ejects 1 to 2 tsp of liquefied contents into the small intestine through the muscular valve ○ stomach contents continue to be ejected in this fashion until stomach is empty and all contents are released in the small intestine Fiber ● dietary fiber ○ non-digestible CHO by human digestive enzymes ○ plants ● functional fiber ○ non-digestible CHO that have been isolated, extracted, or manufactured ○ beneficial physiological effects ● when the diet contains fiber and sufficient fluids ○ bulge of digesting food in the intestine tends to be larger ■ stimulates higher level of intestinal muscle activity than smaller food bulges ● hence, passes through the digestive system somewhat faster than low-fiber meals ● no action occurs in the stomach ● fiber binds to cholesterol and some minerals ● most is excreted with feces ● some fiber is digested by bacteria in the colon GI tract ● if laid flat, the small intestine would be the size of a baseball field (675 square feet) ● requires a high level of nutrients for maintenance ● small intestine = 50% of maintenance met through foods being digested ● large intestine/colon = 80% of maintenance met through foods being digested Completion ● completed when all macronutrients are reduced to substances that can be absorbed ● when vitamins and minerals are released from food Location of Absorption ● small intestine = most nutrients ● large intestine/colon = water, sodium, some products of bacterial digestion ○ contains many strains of bacteria that consume undigested fibers and other complex CHO that are not broken down by the human digestive enzymes ■ bacteria excretes gas and FA that are partly absorbed in the large intestine ■ the rest is excreted in stool ● absorption = a process by which the end products of digestion are taken up by the lymphatic system and the circulatory system ○ followed by distribution to cells of the body Circulatory System ● heart ● arteries ● capillaries ● veins ● responsible for circulating blood through the body ● CHO and protein ● water soluble nutrients Lymphatic System ● network of vessels ● contains a liquid similar to blood ● removes waste ● supports the immune system ● swollen lymph nodes ● absorbs some of the products of digestion ● transports them to the heart, where they are mixed with the substances contained in the blood ● fats ● fat soluble materials ● lymph vessels and blood vessels infiltrate the villi that line the inside of the intestines ● transport absorbed nutrients toward the major branches of the lymphatic and circulatory systems ● fat ○ largely absorbed in the lymphatic system ■ mainly the large chain fatty acids ● CHO and protein ○ largely absorbed through the blood vessels ● nutrient rich contents of the lymphatic system are transferred to the bloodstream near the heart, where blood vessels from both systems merge into one vessel ● lymph and blood mixture is then sent to the heart where its pumped throughout the body by way of the circulatory system ● circulatory system reaches every organ and tissue in the body = supplying cells with nutrients ● cells can use nutrients directly for energy, body structure or the regulation of body processes, or convert them into other usable sources ● CHO ○ glucose vs. glycogen ● fat ○ incorporated into cell membranes or used in the synthesis of hormones ● vitamins and minerals ○ used by cells to control enzyme activity or can be stored for later use ○ vitamin C, thiamin, and sodium are largely excreted in the urine ● CHO = 99% absorbed ● protein = 92% absorbed ● fat = 95% absorbed ● dietary fiber ○ leaves the digestive system as it entered ○ some fiber is digested in the colon by bacteria ● everyone’s digestive system works differently
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