1. The Digestive System BY: MARIEGRACE GANUT

2. Digestive Tracts Not all animals have a digestive tract - Ex. Sponges & protozoa; digestion occurs in food vacuoles - Ex. Hydras (cnidarians); begins in gastrovascular cavity but finishes in food vacuoles Majority of animals have some sort of gut where food is digested into small nutrients needed to sustain the life of cells Digestion contributes to homeostasis by providing the body with nutrients needed to sustain the life of cells Digestive tract: (1) ingests food, (2)breaks food down into small molecules that can cross plasma membranes, (3) absorbs these nutrient molecules, and (4) eliminates undigestible remains *AP – Know homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments

3. Incomplete vs. Complete Tracts INCOMPLETE Has a single opening (mouth), used both as an entrance for & exit for wastes Ex. Planarians (flatworms) - Rely on intracellular digestion to complete the digestive process - Lack of specialized parts Diagram & how/what they eat/digest - p634 in Mader textbook COMPLETE Tract has a mouth & an anus Ex. Earthworms (annelids) - Digestion is extracellular within an intestine - Surface area of digestive tracts is often increased for absorption of nutrient molecules & in earthworms; accomplished by intestinal fold called the typhlosole -Specialization of parts Diagram & how/what they eat/digest – p635 in Mader textbook

4. Continuous vs. Discontinuous Feeders CONTINUOUS Aka filter feeders (clams) constantly “eat” because food is taken in & then pushed out soon afterward One valve opens to siphon (slitlike opening) water the depositing particles, and then the other valve opens to release the filtered water Diagram - p635 Mader textbook DISCONTINUOUS Squids Consume larger meals & store the ingested food for later digestion Diagram – p635 Mader textbook *AP – Know digestive mechanisms in animals such as food vacuoles, gastrovascular activities, one-way digestive enzymes

5. Human Digestive System *AP – KNOW THE PROCESS OF THE DIGESTION OF FOOD

6. Definitions Digestion – a process that breaks down food into molecules that are small enough to enter body cells Absorption – the passage of these smaller molecules through the plasma membranes of cells lining the stomach & intestines and then into the blood and lymph Digestive System – the organs that collectively perform these functions Gastroenterology – medical specialty that deals with the structure, function, diagnosis, and treatment of diseases of the stomach & intestines Proctology – medical specialty that deals with the diagnosis & treatment of disorders of the rectum & anus *lymph – fluid confined in lymphatic vessels & flowing through the lymphatic system until it is returned to the blood

7. Two groups of organs compose the digestive system GASTROINTESTINAL (GI) TRACT OR ALIMENTARY CANAL Continuous tube that extends from the mouth to the anus through the ventral body cavity Organs of GI include the: mouth, most of the pharynx, esophagus, stomach, small intestine, & large intestine Length of the GI tract taken from a cadaver is about 9 m (30 ft) long; in a living person it is much shorter because the muscles along the walls of GI tract organs are in a state of tonus (sustained contraction) ACCESSORY DIGESTIVE ORGANS The teeth, tongue, salivary glands, liver, gallbladder, & pancreas Teeth aid in the physical breakdown of food & tongue consists of swallowing Other accessory digestive organs never come into direct contact with food - They produce or store secretions that flow into the GI tract through ducts; the secretions aid in the chemical breakdown of food

8. GI Tract Contains & processes food from the time it is eaten until it is digested & absorbed or eliminated In some parts of the GI tract, muscular contractions in the wall physically break down the food by churning it; contractions also help to dissolve foods by mixing them with fluids secreted into the tract Enzymes secreted by accessory structures & cells that line the tract break down the food chemically Wavelike contractions of the smooth muscle in the wall of the GI tract move the food along the tract, from the esophagus to the anus

9. o Lumen: central space where food is digested o Mucosa (mucous membrane): produces mucus; protects the wall from the digestive enzymes inside the lumen -either contains glands that secrete and/or receive digestive enzymes from glands that secrete digestive enzymes o Submucosa: broad band of loose connective tissue that contains blood vessels, lymphatic vessels, & nerves; vessel that will carry the nutrients absorbed by the mucosa; help protect from disease o Muscularis: contains 2 layers of smooth muscle; inner layer encircles the tract, the outer longitudinal layer lies in the same direction as the tract o Serosa: secretes a serous fluid; part of the peritoneum, the internal lining of the abdominal cavity

10. Digestive System performs 6 basic processes 1. Ingestion – this process involves taking foods & liquids into the mouth (eating) 2. Secretion – each day, cells within the walls of the GI tract & accessory digestive organs secrete a total of about 7 liters of water, acid, buffers, and enzymes into the lumen of the tract 3. Mixing & propulsion – alternating contraction & relaxation of smooth muscle in the walls of the GI tract mix food & secretions & propel them toward the anus; motility 4. Digestion – mechanical & chemical processes break down ingested food into small molecules

11. Digestive System performs 6 basic processes MECHANICAL DIGESTION The teeth cut & grind food before it is swallowed Smooth muscles of the stomach & small intestine churn the food As a result, food molecules become dissolved & thoroughly mixed w/ digestive enzymes CHEMICAL DIGESTION The large carbohydrate, lipid, protein, & nucleic acid molecules in food are split into smaller molecules by hydrolysis Digestive enzymes produced by the salivary glands (tongue, stomach, pancreas, & small intestine) catalyze these catabolic reactions A few substances in food can be absorbed without chemical digestion - Amino acids, cholesterol, glucose, vitamins, minerals, & water

12. Digestive System performs 6 basic processes 5. Absorption – the entrance of ingested & secreted fluids, ions, & the small molecules that are products of digestion into the epithelial cells lining the lumen of the GI tract; the absorbed substances pass into blood or lymph & circulate to cells throughout the body 6. Defecation – wastes, indigestible substances, bacteria, cells disposed from the lining of the GI tract & digested materials that were not absorbed leaved the body through the anus; eliminated material is termed feces) *AP – Know that cooperative interactions within organisms promote efficiency in the use of energy and matter *AP – Know that organisms exhibit complex properties due to interactions between their constituent parts

13. Functions of the Digestive System 1.Ingestion : taking food into the mouth 2.Secretion : release of water, acid, buffers, & enzymes into the lumen of the GI tract 3.Mixing & propulsion: churning & propulsion of food through the GI tract 4.Digestion: mechanical & chemical breakdown of food 5.Absorption: passage of digested products from the GI tract into the blood & lymph 6.Defecation: the elimination of feces from the GI tract IB – Know how to draw and annotated diagram of the digestive system

14. The Mouth The mouth (oral cavity) serves as the beginning of the digestive tract The palate (roof of the mouth) separates the oral cavity from the nasal cavity - anterior/hard palate and posterior/soft palate The cheeks & lips retain food while it is chewed by the teeth & mixed with saliva There are 3 major pairs of salivary glands: the parotid, submandibular, and siblingual glands Saliva contains the enzyme salivary amylase, which begins the process of starch digestion The disaccharide maltose is a typical end product of salivary amylase digestion Starch + H2O →(Salivary amylase) → maltose The tongue mixes the chewed food with saliva, then forms this mixture into a mass called bolus in preparation for swallowing - Composed of striated muscle & an outer layer of mucous membrane

15. The Pharynx and Esophagus The digestive & respiratory passages come together in the pharynx (throat) and then separate; composed of skeletal muscle & lined by mucous membrane Sphincters (lower gastroespohageal sphincter) – muscles that encircle tubes & act as valves; tubes close when sphincters contract and open when relaxed; relaxes during swallowing & thus allows the bolus to pass from the esophagus into the stomach; located where the esophagus enters the stomach

16. Peristalsis- rhythmical contraction that serves to move the contents along in tubular oragans, such as the digestive tract

17. The Stomach Thick-walled, J-shape organ that lies on the left side of the body beneath the diaphragm; connects the esophagus to the duodenum, the 1 st part of the small intestine Wall of the stomach has deep folds (rugae) that disappear as the stomach fills to an approximate capacity of 1 liter; therefore humans can periodically eat relatively large meals & spend the rest of their time doing other activities Because a meal can be eaten much more quickly than the intestines can digest and absorb it, one of the functions of the stomach is to serve as a mixing chamber & holding reservoir At appropriate intervals after food is ingested, the stomach forces a small quantity of material into the 1 st portion of the small intestine; position & size of the stomach vary continually; when empty, it’s about the size of a large sausage Digestion of starch continues, digestion of proteins and triglycerides begins, the semisolid bolus is converted to a liquid, & certain substances are absorbed *AP – Know functions of the stomach and small intestines

18. The Stomach Epithelial lining of the stomach has millions of gastric acids, which lead into gastric glands So much HCl is secreted by the gastric glands that the stomach routinely has a pH of 2 Such a high acidity usually is sufficient to kill bacteria & other microorganisms that might be in food This low pH also stops the activity of salivary amylase, which functions optimally at the near-neutral pH of saliva As with the rest of the digestive tract, a thick layer of mucus protects the wall of the stomach from enzymatic action An ulcer, an open sore in the wall caused by the gradual destruction of tissues, does occur in some individuals Can be caused by an infection by an acid-resistant bacterium, which is able to attach to the epithelial lining Wherever the bacterium attaches, the lining stops producing mucus, & the area becomes exposed to digestive action; as a result, an ulcer develops *chyme – mixing waves soften food, mix it w/ secretions of the gastric glands, and reduce it to a soup liquid, called chyme

19. The Small Intestine Named for its small diameter, but should be called the long intestine (6 m) Surface area is approximately the size of a tennis court Major event of digestion & absorption occur in the small intestine Provides a large surface area for digestion & absorption; area is further increased by circular folds, villi, and microvilli Divided into 3 regions: duodenum, jejunum, & ileum Duodenum: shortest region, extend 25 cm (10 in.) until it merges with the jejunum Jejunum: about 1 m (3 ft) long & extends to the ileum Ileum: final & longest region of the small intestine, about 2 m (6 ft) long & joins the large intestine Circular folds – permanent ridges in the mucosa; begin near the proximal portion of the duodenum & end at the mid-portion of the ileum; enhance absorption by increasing surface area & causing chyme to spiral, rather than move in a straight line as it passes through the small intestine

20. The Small Intestine ANATOMY OF SMALL INTESTINECIRCULAR FOLDS IB – Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph

21. The Small Intestine Bile – a yellowish, brownish, or olive-green liquid, with a pH of 7.6-8.6 & consists mostly of water & bile acids, bile salts, cholesterol, lecithin, bile pigments, & several ions An excretory product & partially a digestive secretion Bile emulsifies fat; emulsification is the breakdown of large lipid globules into a suspension of droplets & the absorption of lipids following their digestion aka causes fat droplets to disperse in water

22. What factors contribute to increasing its surface area? The wall of the small intestine contains fingerlike projections called villi; vastly increases the surface area of the epithelium available for absorption & digestion and gives the instestinal wall a soft, velvety appearance A villus has an outer layer of columnar epithelial cells, each of these cells has thousands of microscopic extensions called microvilli Give the villi a fuzzy border known as “brush border”; since the microvilli bear the intestinal enzymes, these enzymes are called brush-border enzymes Greatly increase the surface area of the villus for the absorption of nutrients *AP – Know the villi and microvilli

23. The Small Intestine Nutrients are absorbed into the vessels of a villus, which contains blood capillaries & a lymphatic capillary called lacteal Sugars (digested from carbs) & amino acids (digested from proteins) enter the blood capillaries of a villus Glycerol & fatty acids (digested from fats enter the epithelial cells of the villi, and within these cells they are joined & packaged as lipoprotein droplets, which enter a lacteal After nutrients are absorbed, they are eventually carried to all the cells of the body by the bloodstream

24. The Large Intestine Includes the cecum, colon, rectum, & anus Larger in diameter but shorter in length (1.5 m) Absorbs water, salts, & some vitamins; stores undigestible material until it is eliminated at the anus No digestion takes place in the large intestine The cecum, which lies below the junction with the small intestine, is the blind end of the large intestine Has a small, twisted, coiled tube called the vermiform appendix Appendicitis

25. The Large Intestine The colon joins the rectum, the last 20 cm of the large intesting About 1.5 liters of water enters the digestive tract daily An additional 8.5 liters enter the digestive tract each day carrying the various substances secreted by the digestive glands About 95% of this water is absorbed by the small intestine, and much of the remaining portion is absorbed by the colon If this water is not reabsorbed, diarrhea can lead to serious dehydration & ion loss, especially in children Has a population of bacteria, E. Coli, that breaks down undigestible material & also produced some vitamins; vitamin K (necessary to blood clotting)

26. The Large Intestine Digestive wastes eventually leave the body through the anus Feces are about 75% water & 25% solid matter; almost 1/3 of this solid matter is made up of intestinal bacteria The remainder is undigested plant material, fats, waste products (bile pigments), inorganic material, mucus, & dead cells from the intestinal lining The color of feces is the result of bilirubin breakdown & the presence of oxidized iron Foul odor is the result of bacterial action

27. Accessory Organs Organs that assist in digestion but no food passes through them Pancreas – endocrine gland, secrets insulin & glucagon, hormones that help keep the blood glucose level within normal limits Pancreatic cells produce pancreatic juice, which contains sodium bicarbonate and digestive enzymes for all types of food; neutralizes acid chyme from the stomach Pancreatic amylase digests starch, trypsin digests protein, & lipase digests fat Liver – largest gland in the body, contains approx. 100,000 lobules that serve as its structural & functional units Triads, located between the lobules, consist of a bile duct which takes bile away from the liver Hepatic artery – brings O2-rich blood to the liver Hepatic portal vein – transports nutrients from the intestines Liver removes poisonous substances & detoxifies them; removes & stores iron and vitamins A, B12, D, E, & K; makes plasma proteins & helps regulate the quantity of cholesterol in the blood

28. Accessory Organs Liver (cont’d) Maintains the blood glucose level at about 100 mg When insulin is present, any excess glucose present in blood is removed & stored by the liver as glycogen Between meals, glycogen is broken down to glucose, which enters the hepatic veins & in this way, the blood glucose level remains constant If supply of glycogen is depleted, the liver converts glycerol (from fats) & amino acids to glucose molecules Liver produces bile & is stored in the gallbladder Has a yellowish green color b/c it contains the bile pigment bilirubin, derived from the breakdown of hemoglobin, the red pigment of red blood cells Contains bile salts derived from cholesterol & emulsify fat in the small intestine When fat is emulsified, it breaks up into droplets, providing a much larger surface area, which can be acted upon by a digestive enzyme from the pancreas

29. Accessory Organs Liver Disorders Hepatitis & cirrhosis are 2 serious diseases that affect the entire liver & hinder its ability to repair itself Jaundice: present when the skin & the whites of the eyes have a yellowish tinge; bilirubin is deposited in the skin due to an abnormally large amount in the blood; can also result from hepatitis Hepatitis: inflammation of the liver A: sewage-contaminated drinking water B: spread from sexual contact, blood transfusions, or contaminated needles C: contact w/ infected blood, no vaccine, can lead to chronic hepatitis, liver cancer, or death Cirrhosis: often seen in alcoholics, malnutrition & excessive amounts of alcohol the liver is forced to break down Gallbladder – pear-shaped, muscular sac attached to the surface of the liver About 1,000 ml of bile are produced by the liver each day & any excess is stored in the gallbladder Water is reabsorbed by the gallbladder so that bile becomes a thick, mucuslike material When needed, bile leaves the gallbladder & proceeds to the duodenum via the common bile duct Cholesterol content of bile can come out of solution & form crystals If crystals grow in size, gallstones form Passage of the stones from the gallbladder may block the common bile duct & cause obstructive jaundice Gallbladder must be removed

30. LARGE INTESTINEACCESSORY ORGANS Diagram on page 640 in Mader textbook

31. Digestive Enzymes Watch this video to review enzymes Proteins Used to start reactions Lowers activation energy They are catalysts

32. Digestive Enzymes Help break down carbohydrates, proteins, nucleic acids, & fats Starch is a polysaccharide & its digestion begins in the mouth Saliva has a neutral pH & contains salivary amylase, the 1 st enzyme to act on starch Maltose molecules can’t be absorbed by the intestine; additional digestive action in the small intestine converts maltose to glucose, which can be absorbed Protein digestion begins in the stomach Gastric juice secreted by gastric glands has a very low pH, about 2, because it contains HCl Pepsinogen, a precursor that’s converted to pepsin when exposed to HCl, is also present in gastric juice; pepsin acts on protein to produce peptides Peptides are usually too large to be absorbed by the intestinal lining, but later they are broken down in the small intestine Quick review from the 1 st quarter… Carbohydrates – class of organic compounds that includes monosaccharides, di-, & poly- Mono – simple sugar; a carbohydrate that can’t be decomposed by hydrolysis Di – sugar that contains 2 units of monosaccharide Poly – Polymer made from sugar monomers Proteins – Molecule consisting of one or more polypeptides Polypeptide – polymer of many amino acids linked by peptide bonds Polymer- macromolecule consisting of covalently bonded monomers Monomers – small molecule that is a subunit of a polymer Nucleic acids – polymer of nucleotides Nucleotides - monomer of DNA & RNA consisting of a 5-C sugar bonded to a nitrogenous base & phosphate group *AP – Know degradation Degradation – reduction of a chemical compound to one less complex by splitting off one or more groups

33. Digestive Enzymes Starch, proteins, nucleic acids, & fats are all enzymatically broken down in the small intestine Pancreatic juice, which enters the duodenum, has a basic pH because it contains NaHCO3 A pancreatic enzyme, pancreatic amylase, digests starch Maltase & peptidases, enzymes produced by the small intestine, complete the digestion of starch to glucose & protein to amino acids Glucose & amino acids are small molecules that cross into the cells of the villi & enter the blood Maltose, a disaccharide that results from the first step in starch digestion, is digested to glucose by maltase Other disaccharides have their own enzyme & are digested in the small intestine; the absence of any one of these enzymes can cause illness

34. Digestive Enzymes Peptides, which result from the 1 st step in protein digestion, are digested to amino acids by peptidases Lipase digests fat molecules in fat droplets after they have been emulsified by bile salts The end products of lipase digestion are monoglycerides (glycerol + one fatty acid) & fatty acids These enter the villi, and within these cells, they are rejoined & packaged as lipoprotein droplets called chylomicrons, and they enter the lacteals

35. Application *IB - Use of dialysis tubing to model absorption of digested food in the small intestine Remember the diffusion and osmosis lab? Dialysis tubing made from cellulose has pores in it that allow water and small molecules & ions to pass through freely, but not large molecules. Like how starch, proteins, nucleic acids, & fats are all enzymatically broken down in the small intestine. Chyme entering the small intestine contains partially digested carbs, proteins, & lipids.

36. QUIZ Next class No notes Know your diagrams Know your definitions

37. Human Nutrition

38. Nutrients – chemical substances in food that body cells use for growth, maintenance, & repair 6 main types of nutrients: water, carbohydrates, lipids, proteins, minerals, & vitamins Water is the nutrient needed in the largest amount – about 2 to 3 liters per day Carbs, lipids, & proteins provide the energy needed for metabolic reactions & serve as building blocks to make body structures Some minerals & many vitamins are components of the enzyme system that catalyze metabolic reactions Essential nutrients – specific nutrient molecules that the body cannot make in sufficient quantity to meet its needs & must be included in the diet (*IB)

39. Minerals Inorganic elements that occur naturally in the Earth’s crust In the body they appear in combination with each other, in combination with organic compounds, or as ions in solution Constitute about 4% of total body mass & are concentrated most heavily in the skeleton Mineral with known functions in the body include: calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium, iron, iodide, manganese, copper, cobalt, zinc, fluoride, selenium, & chromium The body generally uses the ions of the minerals rather than the non-ionized form; ex. Chlorine (toxic or even fatal if ingested in the non-ionized form) Some attention must be paid to eating foods that provide enough calcium, phosphorus, iron, & iodide; excess amounts of most minerals are excreted in the urine & feces *IB – Know which dietary minerals are essential chemical elements

40. Minerals Calcium & phosphorus form part of the matrix of bone Because minerals do not form long-chain compounds, they are otherwise poor building materials Major role of minerals is to help regulate enzymatic reactions Calcium, iron, magnesium, & manganese are constituents of some coenzymes Magnesium serves a s a catalyst for the conversion of ADP to ATP Sodium & phosphorus work in buffer systems, which help control the pH of body fluids; sodium also helps regulate osmosis of water & along with other ions, is involved in the generation of nerve impulses http://www.thetotalman.com/body/mineral-chart.htmhttp://www.thetotalman.com/body/mineral-chart.htm (Minerals vital to the body)

41. Vitamins Organic nutrients required in small amounts to maintain growth & normal metabolism Unlike carbs, lipids, or proteins, vitamins do not provide energy or serve as the body’s building materials; most vitamins with known functions are coenzymes Most vitamins can’t be synthesized by the body & must be ingested in food Vitamin K The body can assemble some vitamins if the raw materials (provitamins) are provided Ex. Vitamin A is produced by the body from the provitamin beta-carotene, a chemical present in yellow vegetables such as carrots & dark green vegetables such as spinach No single food contains all the require vitamins, one of the best reasons to eat a varied diet *IB – vitamins are chemically diverse carbon compounds that cannot be synthesized by the body

42. Vitamins FAT SOLUBLE Vitamins A, D, E, and K are absorbed along with other dietary lipids in the small intestine & packaged into chylomicrons; cannot be absorbed in adequate quantity unless ingested with other lipids May be stored in cells, particularly hepatocytes WATER SOLUBLE Include several B vitamins & vitamin C Dissolved in body fluids Excess quantities of these vitamins are not stored but instead exreted in the urine

43. Vitamins Besides their other functions, 3 vitamins, C, E, & beta-carotene (provitamin) are termed antioxidant vitamins because they inactivate oxygen free radical Free radicals are highly reactive ions or molecules that carry an unpaired electron in their outermost electron shell Free radicals damage cell membranes, DNA, & other cellular structures and contribute to the formation of artery-narrowing atherosclerotic plaques Some free radicals arise naturally in the body & others derive from environmental hazards such as tobacco smoke & radiation Thought to play a role in: protecting against some kinds of cancer, reducing the buildup of atherosclerotic plaque, delaying some effects of aging, & decreasing the chance of cataract formation in the lens of the eyes

44. Vitamins Most nutritionists recommend eating a balanced diet that includes a variety of foods rather than taking vitamin or mineral supplements, except in special circumstances Because most North Americans don’t ingest in their food the high levels of antioxidant vitamins thought to have beneficial effects, some experts recommend supplementing vitamins C & E More is not always better, however; larger doses of vitamins or mineral can be very harmful http://www.thetotalman.com/body/vitamin-chart.htmhttp://www.thetotalman.com/body/vitamin-chart.htm (Principal vitamins) http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Nutrition.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Nutrition.html (More on vitamins) Application: *IB - Lack of vitamin D or calcium can affect bone mineralization & cause rickets (softening & weakening of bones) in children or osteomalacia (softening of bones, more likely to bow & fracture) in adults; possible loss of muscle tone *IB – malnutrition is an imbalance of total caloric intake or intake of specific nutrients, which can be either inadequate or excessive

45. Carbohydrates Present in food in the form of sugars, starch & fiber Fruits, vegetables, milk, & honey are natural sources of sugars Glucose & fructose are monosaccharide sugars, and lactose (milk sugar) & sugar (table sugar) are disaccharides After being absorbed from the digestive tract into the bloodstream, all sugars are converted to glucose for transport in the blood & use by cells; glucose is the preferred direct energy source in cells Plants store glucose of starch & animals store glucose as glycogen; starch is digested to glucose in the digestive tract, & any excess glucose is store as glycogen

46. Carbohydrates Fiber includes various undigestible carbs derived from plants Food sources rich in fiber include beans, peas, nuts, fruits, & vegetables Whole-grain products are a good source of fiber, therefore are more nutritious than food products made from refined grains; during refinement, fiber, vitamins, & minerals are removed from grains so that primarily starch remains Ex. Slice of bread Technically, fiber is not a nutrient for humans because it can’t be digested to small molecules that enter the bloodstream Insoluble fiber adds bulk to fecal material, which stimulates movement in the large intestine, preventing constipation Soluble fiber combines with bile acids & cholesterol in the small intestine & prevents them from being absorbed High-fiber diets may protect against heart disease

47. Carbohydrates Carbs should supply a large portion of energy needs Nutritionists hypothesize that the high intake of foods that are rich in refined carbs and fructose sweeteners processed from cornstarch may be responsible for the prevalence of obesity in the US Because certain foods (donuts, cakes, pies, cookies) are high in both refined carbs & fat, it’s difficult to determine which dietary component is responsible for the current epidemic of obesity In any case, they are empty-calorie foods that provide sugars but no vitamins or minerals; nutritionists point out that consuming too much energy from any source contributes to body fat, increasing a person’s risk of obesity & associated illnesses

48. *IB – Determination of the energy content of food by combustion Foods, depending on their carbohydrate/fat composition, have different energy content that can be determined by measuring the heat release from their combustion. Determine the amount of heat released by a substance given the specific heat capacity (Cp) of water, the mass (m) of the food sample and the change in temperature (∆t) Equation for the calculation of the heat released/absorbed of a substance given the mass of the substance and the specific heat of that substance: q = Cp X m X ∆t where Cp is the specific heat, or the heat needed to raise the temperature of 1 g by 1 K m is the mass of the substance ∆t = final temperature – initial temperature

49. Lipids Like carbs, triglycerides (fats & oils) supply energy for cells, but fat is stored for the long term in the body Recommended that people include unsaturated, rather than saturated, fats in their diets; 2 unsaturated fatty acids (alpha-linolenic & linoleic acids) are essential in the diet Delayed growth & skin problems can develop in people whose diets lack these essential unsaturated fatty acids Animal-derived foods (butter, meat, whole milk, & cheeses) contain saturated fatty acids; plant oils contain unsaturated fatty acids, each type of oil has a particular percentage of monounsaturated & polyunsaturated fatty acids Cholesterol, a lipid, can be synthesized in the body; cells use cholesterol to make various compounds, including bile, steroid hormones, & vitamin D Plant foods don’t contain cholesterol

50. Lipids Elevated blood cholesterol levels are associated with an increased risk of cardiovascular disease, the #1 killer of Americans; a diet rich in cholesterol & saturated fats increases the risk of cardiovascular disease Studies suggest that trans-fats are even more harmful than saturated fats Found in commercially packaged foods (cookies & crackers), commercially fried foods (French fries), & packaged snacks Trans-fats arise when unsaturated oils are hydrogenated to produce a solid fat, as in shortening and some margarines Trans-fats may reduce the function of the plasma membrane receptors that clear cholesterol from the bloodstream *IB – Some fatty acids and some amino acids are essential

51. Proteins Dietary proteins are digested to amino acids, which cells use to synthesize hundreds of cellular proteins; of the 20 different amino acids, 9 are essential amino acids that must be present in the diet Eggs, milk products, meat, poultry, & most other foods derived from animals contain all 9 essential amino acids & are considered “complete” or “high-quality” protein sources Foods derived from plants general don’t have as much protein per serving as those derived from animals, & each type of plant food generally lacks one or more of the essential amino acids; therefore most plant foods are “incomplete” or “low-quality” protein sources Grains, beans, nuts in various combos, tofu, soymilk, & other foods made from processed soybeans are complete protein sources; for vegetarians & vegans

52. Proteins Protein shouldn’t supply the bulk of dietary calories Ex. Body builders should realize that excess amino acids are not always converted into muscle tissue When amino acids are broken down, the liver removed the nitrogen portion & uses it to form urea, which is excreted in urine The water needed for excretion of urea can cause dehydration when a person is exercising & losing water by sweating High-protein diets can also increase calcium loss in the urine & encourage the formation of kidney stones High-protein foods often contain a high amount of fat *IB – Lack of essential amino acids affects the production of proteins

53. Type 2 Diabetes Indicated by the presence of glucose in the urine Glucose has spilled over into the urine because there is too high a level of glucose in the blood Increasing rapidly in most industrialized countries around the world A healthy diet, increased physical activity, & weight loss have been seen to improve the ability of insulin to function properly in type 2 diabetes All diabetics, whether type 1 or type 2, are at risk for blindness, kidney disease, as well as cardiovascular disease *IB – Overweight individuals are more likely to suffer hypertension and type II diabetes

54. Quick Overview of Diabetes TYPE 1 Pancreas does not produce insulin & patient must have daily insulin injections TYPE 2 Children (becoming more prevalent) & more often adults are usually obese Display impaired insulin production & insulin resistance The body’s cells fail to take up glucose, even when insulin is present The blood glucose level exceeds the normal level & glucose appears in the urine

55. Cardiovascular Disease Cardiovascular disease (hypertension, heart attack, & stroke) is among the leading cause of death in the US Often due to arteries blocked by plaque, which contains saturated fats & cholesterol Cholesterol is carried in the blood by 2 types of lipoproteins: low-density lipoprotein & high- density lipoprotein Application: *IB – cholesterol in blood as an indicator of the risk of coronary heart disease

56. Cholesterol LOW-DENSITY LIPOPROTEIN (LDL) Considered “bad” because they are like delivery trucks that carry cholesterol from the liver to the cells & to the arterial walls Consuming saturated fats & trans-fats tend to raise LDL cholesterol levels, while eating unsaturated fats lower LDL cholesterol levels Olive & canola oils, most nuts, & cold water fish tend to lower LDL cholesterol levels HIGH-DENSITY LIPOPROTEIN (HDL) Considered “good” because they are like garbage trucks that dispose of cholesterol Transports cholesterol from the cells to the liver, which converts it to bile salts that enter the small intestine

57. Cholesterol Coldwater fish (herring, sardines, tuna, & salmon) contain polyunsaturated fatty acids & especially omega- 3 unsaturated fatty acids, which are believed to reduce the risk of cardiovascular disease However, taking fish oil supplements to obtain omega-3s is not recommended without a physician’s approval because too much of these fatty acids can interfere with normal blood clotting American Heart Association recommends limiting total cholesterol intake to 300 mg per day; requires careful selection of the foods included in daily diets Ex. Egg yolk contain about 210 mg of cholesterol, which would be 2/3 of the recommended daily intake, but doesn’t mean eggs should be eliminated from a healthy diet Most people can eat a couple of whole eggs each week without experiencing an increase in their blood cholesterol levels Physicians can determine whether patients’ blood lipid levels are normal If a person’s cholesterol & triglyceride levels are elevated, modifying the fat content of the diet, losing excess body fat, & exercising regularly can reduce them If lifestyle changes don’t lower blood lipid levels enough to reduce the risk of cardiovascular disease, a physician may prescribe special medications *AP – DNA, and in some cases RNA, is the primary source of heritable information

58. *IB – Use of databases of nutritional content of foods and software to calculate intakes of essential nutrients from a daily diet

59. Hypothalamus Hypothalamus regulates food intake & drinking Contains a thirst center When certain cells in the hypothalamus are stimulated by rising osmotic pressure of the extracellular fluid, they cause the sensation of thirst The intake of water by drinking restores the osmotic pressure to normal, removing the stimulation & relieving the thirst Lateral hypothalamus controls hunger; damage to this area can cause reduced food intake, presumably through loss of appetite & stimulation of this area can increase appetite Influences glucose metabolism & through the body’s inclination towards homeostasis can increase/decrease blood sugar levels through insulin secretion to increase or decrease appetite Ventromedial hypothalamus – when stimulated, makes you feel full If your ventromedial hypothalamus was removed… You would never feel full again *IB – Appetite is controlled by a center in the hypothalamus

60. Anorexia Nervosa Chronic disorder characterized by self-induced weight loss, negative perception of body image, & physiological changed that result from nutritional depletion Have a fixation on weight control & often insist on having a bowel movement every day despite inadequate food intake Often abuse laxatives, which worsens the fluid & electrolyte imbalances & nutrient deficiencies *IB – Starvation can lead to breakdown of body tissue Application: *IB – Breakdown of heart muscle due to anorexia As the body loses muscle mass, it loses heart muscle at a preferential rate; the heart gets smaller & weaker About half of all anorexics have low white blood cell counts & about a third are anemic Conditions can lower the immune system’s resistance to disease, leaving a person vulnerable to infections

61. Applications *IB – Production of ascorbic acid by some mammals, but not others that need a dietary supply Humans are one of the few mammals unable to manufacture ascorbic acid in their livers Vitamin C (ascorbic acid) must be consumed from supplement or diet Absence of the enzyme I-gulonolactone oxidase from the liver was implicated A defect or loss of the gene controlling the synthesis of this enzyme in humans blocks the final phase in the series for converting glucose to ascorbic acid Deficiency: scurvy – characterized by tender swollen gums, loosening of teeth, poor wound healing, bleeding, & retardation of growth http://www.hammernutrition.com/knowledge/humans-lack-the-ability-to-make-vitamin- c.278.htmlhttp://www.hammernutrition.com/knowledge/humans-lack-the-ability-to-make-vitamin- c.278.html (For more info)

62. Applications *IB – Cause and treatment of phenylketonuria (PKU) Rare inherited disorder that causes an amino acid (phenylalanine) to build up in the body; caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine Without the enzyme necessary to process phenylalanine, a dangerous buildup can develop when a person with PKY eats foods that are high in protein (milk, cheese, nuts, meat); can eventually lead to serious health problems People with PKU need to follow a diet that limits phenylalanine, which is found mostly in foods that contain protein Treatments: a lifetime diet with very limited intake of protein, taking a PKU formula (special nutritional supplement) to make sure there is enough essential protein (without phenylalanine) and nutrients that are crucial for growth & general health, and the FDA approved drug sapropterin (Kuvan) that increases tolerance to phenylalanine

63. Reminder Quiz next class on The Digestive System No notes Know your diagrams Know your definitions

64. Recap of Digestive System

66. Bibliography Mader, Sylvia S. "Digestive Systems and Nutrition." Biology. 10th ed. N.p.: n.p., n.d. 634-45. Print. Grabowski, Sandra Reynolds. "The Digestive System." Principles of Anatomy and Physiology. By Gerard J. Totora. 10th ed. N.p.: n.p., n.d. 851-900; 936-941. Print. http://www.webmd.com/mental-health/eating-disorders/anorexia-nervosa/features/anorexia- body-neglectedhttp://www.webmd.com/mental-health/eating-disorders/anorexia-nervosa/features/anorexia- body-neglected http://mayoclinic.org/