Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh Edition Solomon Berg Martin Chapter 45 Processing Food and Nutrition

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Heterotrophs Organisms that obtain nourishment from the organic molecules manufactured by other organisms Nutrients used to Run the systems of the body Make compounds for metabolic processes Grow and repair tissue

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Nutrition Process of taking in and using food Malnutrition results from dietary intake that is either below or above required need –Undernutrition (particularly protein deficiency) –Obesity (common in the US)

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Food processing Ingestion –Taking of food into the digestive cavity Digestion –Process of breaking down food mechanically and chemically Absorption –Nutrients pass through the lining of the digestive tract and into the blood

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Food processing, cont. Egestion or elimination –Food that is not digested and absorbed is discharged from the body

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition In cnidarians and flatworms Food is digested in the gastrovascular cavity The gastrovascular cavity serves as both mouth and anus

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Simple invertebrate digestive systems

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition In more complex invertebrates and in all vertebrates The digestive tract is a complete tube with an opening at each end Digestion takes place as food passes through the tube

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Digestive tract with two openings

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Various parts of the digestive tract are specialized to perform specific functions Food passes in sequence through The mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Human digestive system

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Mechanical and enzymatic digestion of carbohydrates begin in the mouth Mammalian teeth include incisors for biting, canines for tearing, and premolars and molars for crushing and grinding Three pairs of salivary glands secrete saliva

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Teeth and diet

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Tooth structure

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition As food is swallowed, it is propelled through the pharynx and esophagus A bolus of food is moved by peristalsis The mixing and propulsive movements of the digestive tract are known as motility

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Peristalsis

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition In the stomach Food is mechanically digested by vigorous churning Proteins are enzymatically digested by pepsin Rugae are stomach folds that expand with food Gastric glands secrete hydrochloric acid and pepsinogen

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Structure of the stomach

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition After several hours in the stomach Chyme leaves the stomach through the pylorus and enters the small intestine Most enzymatic digestion takes place in the duodenum The liver produces bile, which emulsifies fats

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition After several hours in the stomach, cont. The pancreas releases enzymes that digest protein, lipid, and carbohydrates, as well as RNA and DNA The large intestine eliminates undigested waste and incubates bacteria that produce Vitamin K and certain B vitamins

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition The liver and pancreas

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Digestion of carbohydrate, protein, and lipid Nutrients in chyme are enzymatically digested as they move through the digestive tract Polysaccarides are digested to the disaccharide maltose by salivary and pancreatic amylases

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Digestion of carbohydrate, protein, and lipid, cont. Maltase splits maltose into glucose Proteins are split by pepsin and by proteolytic enzymes into the final product of amino acids Lipids are emulsified by bile salts and then hydrolyzed by pancreatic lipase

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Summary of digestion

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Some hormones that regulate digestion

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Structural adaptations that increase the surface of the digestive tract The surface area of the small intestine is greatly expanded by –Folds in its wall –Intestinal villi –Intestinal microvilli

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Villi and microvilli

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Lipid absorption Nutrients are absorbed through the thin walls of the intestinal villi The hepatic portal vein transports amino acids and glucose to the liver

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition How the body uses fat

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Absorption of other nutrients Fatty acids and monacylglycerols enter epithelial cells in the intestinal lining where they are reassembled into triacyglycerols They are packed into chylomicrons The lymphatic system transports chylomicrons to the blood circulation

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Nutritional requirements for dietary carbohydrates Most carbohydrates are ingested in the form of complex carbohydrates Fiber is a mixture of cellulose and other indigestible carbohydrates Carbohydrates are used mainly as an energy source

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Lipids are used as An energy source Components of cell membranes To synthesize steroid hormones and other lipid substances Most lipids are ingested in the form of triacyglycerols

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Proteins Serve as enzymes Are essential structural components of cells The best distribution of essential amino acids is found in the complex proteins of animal foods

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition How the body uses protein

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Vitamins Organic compounds required in small amounts for many biochemical processes Many serve as components of coenzymes

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Vitamins, cont. Fat-soluble vitamins include A, D, E, and K Water-soluble vitamins are the B and C vitamins

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition The vitamins

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Minerals are inorganic nutrients ingested as salts dissolved in food and water Trace elements are minerals required in amounts less than 100 mg per day

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Some important minerals and their functions

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Basal metabolic rate (BMR) The body’s cost of metabolic living Total metabolic rate BMR plus the energy used to carry on daily activities

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Energy input and output When energy (kilocalories) input equals energy output, body weight remains constant When energy input exceeds energy output, body weight increases When energy output exceeds energy input, body weight decreases

Copyright © 2005 Brooks/Cole — Thomson Learning Biology, Seventh EditionCHAPTER 45 Processing Food and Nutrition Current hypotheses regarding the regulation of food intake and energy homeostasis Researchers are identifying signaling molecules –The hormone leptin –The neuropeptite Y (NPY), a neurotransmitter produced in the hypothalamus