KNES 3260, Week 4 notes
KNES 3260, Week 4 notes KNES 3260
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This 50 page Class Notes was uploaded by Jessica Roberts on Sunday September 18, 2016. The Class Notes belongs to KNES 3260 at University of North Carolina at Charlotte taught by Mrs. Tracy Bonoffsk in Fall 2016. Since its upload, it has received 141 views. For similar materials see Nutrition in Kinesiology at University of North Carolina at Charlotte.
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Date Created: 09/18/16
Chapter 3: Digestion, Absorption, and Metabolism Chapter 4: Carbohydrates in Our Food Chapter 3 Digestion, Absorption, and Metabolism From Atoms to Organisms The organization of life begins with atoms that form molecules, which are then organized into cells to form tissues, organs, and whole organisms Most organs do not function alone but are part of an organ system Some organs are part of multiple organ systems Organ Systems of the Body An organ may be part of more than one organ system. Ex. Pancreas is part of the endocrine system as well as the digestive system. Organ systems work together to support the entire organism o The endocrine system secretes hormones that help food intake and the function of digestive organs. o The nervous system aids in digestion by sending serve signals that help control the passage of food through the digestive tract. o Once absorbed, nutrients are transported to individual cells by the cardiovascular system. The body’s urinary, respiratory, and integumentary systems allow the elimination of metabolic waste products Digestive System The 2 functions of the digestive system are digestion and absorption Gastrointestinal tract Transit time-this is about 24-72 hours Amount of time it takes food to pass the length of the GI tract. It is affected by the composition of the diet, physical activity, emotions, medications, and illness High amounts of carbs or juice have quick transit times; while high fat foods, high protein foods or solid foods are slow to transit Feces Body waste, including unabsorbed food residue, bacteria and dead cells Figure 3.2 The digestive system includes the GI organs (mouth, pharynx, esophagus, stomach, small intestine and large intestine) and the accessory organs (salivary glands, liver, gallbladder, and pancreas) The general set up of the wall of GI tract contains 4 layers of tissue (which are made out of connective tissue and smooth muscle). Digestive Secretions Digestion inside lumen of the GI tract is assisted by digestive secretions. One of these secretions is mucus Mucus Viscous material produced by cells in the mucosal lining of the gut; mucus moistens, lubricates and protects the GI tract Enzymes Are protein molecules that speed up chemical reactions without themselves being consumed or changed by the reactions In digestion, enzymes accelerate the breakdown of nutrients Table 3.2: Digestive Enzyme Functions (shortened) Enzyme Where it is Where it works What it does Salivary amylase Salivary glands Mouth Breaks down starch Lingual lipase Lingual glands in tongue Mouth Breaks down triglycerides Pepsin Stomach Stomach Breaks down proteins Gastric lipase Stomach Stomach Breaks down triglycerides Trypsin Pancreas Small Intestine Breaks down proteins Chymotrypsin Pancreas Small Intestine Breaks down proteins Carboxypeptidase Pancreas Small Intestine Breaks polypeptides and amino acids Pancreatic lipase Pancreas Small Intestine Breaks down triglycerides Pancreatic amylase Pancreas Small Intestine Breaks down starch Aminopeptidase and Small Intestine Small Intestine Breaks down polypeptides dipeptidase Sucrase Small Intestine Small Intestine Breaks down sucrose Lactase Small Intestine Small Intestine Breaks down lactose Maltase Small Intestine Small Intestine Breaks down maltose Figure 3.3-How Digestive Enzymes work Enzymes speed up chemical reactions without themselves being altered by the reaction. In this example, the enzyme amylase helps break a large carbohydrate molecule (a starch molecule from bread) into 2 smaller ones Table 3.3: Digestive Hormones (shortened version) Hormone Where it comes from What it does Gastrin Stomach mucosa Stimulates secretion of HCl Ghrelin Stomach mucosa Stimulates appetite and increases gastric emptying Secretin Duodenal mucosa Inhibits gastric secretion and motility and increases output of water and bicarbonate from the pancreas Cholecystokinin (CCK) Duodenal mucosa Stimulates contraction of the gallbladder to expel bile Gastric inhibitory peptide Duodenal mucosa Inhibits gastric secretion and motility Mouth Cephalic phase (the start of digestion) Sense of smell and sight The mouth is the entry point for food into the digestive tract The presence of food in the mouth stimulates the flow of saliva from the salivary glands located at the sides of the face and below and in front of the ears Saliva contains salivary amylase, which helps to break down carbohydrates and lysozymes, which help to inhibit bacterial growth in the mouth Chewing mechanically breaks food down, increasing the surface area in contact with digestive enzymes Pharynx and Epiglottis: Figure 3.4 o The tongue initiates swallowing by moving the rounded mass, or bolus, of chewed food mixed with saliva back toward the pharynx o The pharynx is shared by the digestive tract and the respiratory tract o We are able to start the muscular contractions of swallowing by choice, but once initiated swallowing becomes involuntary and proceeds under the control of nerves. Esophagus: Figure 3.5 o The food we swallow is pushed along by the rhythmic muscular contractions of peristalsis. o Food enters the stomach in response to the opening and closing of the gastroesophageal sphincter, located where esophagus meets the stomach The stomach Chyme The substance mixed with gastric enzymes After chyme goes through the pyloric sphincter, it goes into the small intestine and mixes with pancreatic enzymes Gastric juices is the collective name for stomach secretions It is a mixture of water, mucus, HCl, and pepsinogen Pepsinogen is an inactive protein-digesting enzyme produced by gastric glands and activated to pepsin by acid in the stomach Stomach: Figure 3.6a o The stomach wall contains 3 layers of smooth muscle, which contract powerfully to mix food o They are the longitudinal, circular, and diagonal. Lining of the Stomach (Figure 3.6b) The lining of the stomach is dotted with gastric pits. Inside these pits are the gastric glands, made up of different types of cells that produce the components of gastric juice Mucous cells, parietal cells, and chief cells secrete mucus, hydrochloric acid (HCl) and pepsinogen, into the lumen of the stomach Regulation of stomach activity: Figure 3.7 Stomach activity is affected by food that has not yet reached the stomach, by food that is in the stomach, and by food that has left the stomach Meal Composition and Hunger: Figure 3.8 What you choose for breakfast can affect when you become hungry for lunch. Toast and coffee will leave your stomach quickly. A larger meal with more protein and fat such as bacon, eggs and buttered toast leaves the stomach more slowly, keeping you full longer Structure of the small intestine The small intestine performs absorption of nutrients Most digestion occurs in the small intestine It has several layers to maximize absorption Intestinal wall has large circular folds, which increase surface area in contact with nutrients All of the inner surface is covered with finger-like projections called villi The mucosal cells on the surface of each villi are covered with tiny microvilli, often called brush border Enzymes from the accessory organs (liver, pancreas, and gallbladder) go into the small intestine Ex: Pancreatic amylasestarchdisaccharide monosaccharide Ex: Pancreatic lipasetriglyercidesfatty acids Segmentation occurs in the small intestine This movement mixes food with intestinal juices and brings it in contact with the intestinal wall. Gallbladder, Liver, and Pancreas Gallbladder stores bile which is secreted by the liver Fat is not stored in water, so bile breaks down fat into large droplets. These droplets become globules, allowing lipases to access and digest the fat molecules more efficiently Pancreas secretes digestive enzymes and bicarbonate ions into the small intestine during digestion Absorption mechanisms Simple diffusion Substances that can pass freely across the mucosal cell membrane Ex. fatty acids Osmosis The passage of water molecules from an area with lower concentration of dissolved substances Ex. glucose Facilitated diffusion A type of passive diffusion that requires a carrier molecule. Ex. fructose Active Transport Requires energy and a carrier molecule Ex. Amino acids Large Intestine It consists of the colon, rectum and anus The large intestine can absorb water and some vitamins and minerals, fibers and leftover carbs Intestinal microflora (the bacteria microorganisms living in the colon) They produce nutrients (such as vitamin B and vitamin K (which is responsible for blood clotting) They produce the by-product gas Water, nutrients and fecal material may spend up to 24 hours in the large intestine. It takes 3-5 hours for chyme to move through the small intestine Antibiotics can wipe out the flora in the large Intestine Intestinal Microbiota The proper mix of microorganisms in the intestinal microbiota is important for optimal gastrointestinal function, maintenance of immune function and/or overall health The presence of microbiota and the substances it produces helps maintain the mucosal layer that lines the intestine and serves as a barrier, modulate the amount of inflammation in the gut, prevent the growth of disease- causing bacteria An improper mix of healthy microbiota may overstimulate the immune system, leading to excess inflammation. Ex. People with inflammatory bowel disease, irritable bowel syndrome, and colon cancer Intestinal Microbiota cont’d Fibers serve as a food supply for the beneficial bacteria are called prebiotics The consumption of healthy live beneficial bacteria (probiotics) Ex. Lactobacillus (in yogurt)-they inhibit the growth of harmful bacteria The issues of capsulated probiotics is that they may not be enough, the bacteria may have died or the body isn’t absorbing it well Figure 3.13: Gut microbiota, nutritional status, and health What we eat affects the gut microbiota, and the gut microbiota in turn enables the digestion of substances that can’t be broken down by human enzymes A healthy microbiota helps prevent the growth of disease-causing organisms and moderate inflammation. GI’s role in Immune System Health The GI tract plays an important role in protecting the body from infection The GI tract limits the absorption of toxins and disease-causing organisms The norovirus is a bacteria that causes the stomach bug Peyer’s patches are patches of immune system cell in the GI tract The white blood cells that live in the GI tract: Phagocytes (are the first type of cells that come to the body’s defense; they attack/engulf any invader) Lymphocytes (they attack specific antigens) Food allergies and Gluten Food allergies occur when the body sees a food protein called an allergen, as a foreign substance The first time the protein is consumed, a piece of protein stimulates the immune system Gluten-related disorders is the term used to describe a group of conditions that cause reactions to gluten- containing foods. They include celiac disease, non celiac gluten sensitivity and wheat allergy Common Digestive Problems: Heartburn and GERD GERD (aka heartburn). The symptoms are as follows: Discomfort Ulcers (in esophagus) Esophageal cancer Barets esophagus (scar tissue areas in the esophagus) Treatment: Change diet (avoiding fatty foods, spicy/acidic food [spaghetti or pizza], high sodium food [frozen food, Chinese food], chocolate, high caffeinated foods) Losing weight (pressure from fat; includes pregnancy) stomach to produce more acid) these would cause kidney stones and can cause the Not eating large amounts of food 2-3 hours before bed Surgery to close sphincter (for severe cases) Common Digestive Problems cont’d Peptic Ulcers Occur if GERD is left untreated They are open sores in the lining of the stomach, esophagus, or small intestine Helicobacter pylori (H. pylori) is the leading cause of ulcers Pancreatic and gallbladder problems Pancreatic Problems Examples: Pancreatic cancer and pancreatitis If the pancreas is not functioning normally, the availability of enzymes needed to digest carbs, fat, and protein may be reduced, thus limiting the ability to digest and absorb them Gallbladder Problems The most common condition is gallstones If gallbladder is not releasing bile, fat absorption can be impaired Diarrhea Imbalances in the bacteria in the GI tract that causes imbalances in fluid/water; it’s the body’s way to get rid of the bacteria that caused it; it is an issue for children or elderly because it can be life threatening Remedy: drink more fluids/electrolytes Constipation The issue behind this is that it can lead to outpouchings in the colon called diverticula and allows toxic waste products to get absorbed into the body Remedy: high fiber, high-fluid diet, exercise, and medications Common Digestive Problems cont’d IBS (Irritable Bowel Syndrome) It is common in 20-30 age group, usually in women Bowel issues that fall into this categories It is very annoying These patients should write down their diet to see what is the trigger Alternate feeding methods Enteral feeding (aka tube-feeding) can be delivered by a narrow tube passed through the nasal passages and into the stomach or intestine so that a liquid diet (specialized formula) can be delivered for digestion and absorption If a person’s GI tract is not functional, total parenteral nutrition (TPN) can deliver a solution providing all of the essential nutrients directly into the bloodstream through a large vein in the upper arm or chest Types of patients: Someone with cancers (stomach or throat) Someone with a history of stroke Someone with a history of a coma Downsides to these method Increased risk for acid reflux (via tube-feeding) Increased risk of infection Lack of activity from the stomach (via TPN) Involves the expertise of a nurse or dietician Digestive System throughout life Figure 3.17 There are some differences in the way the digestive system functions during pregnancy, infancy, and with advancing age In older adults, dry mouth is common and can make swallowing difficult During pregnancy, hormonal changes can cause nausea and vomiting (morning sickness) Young infants, although they have no teeth and can’t consume solid foods, they have digestive enzymes suited to the digestion of the lipids, proteins, and carbs in human milk Children and adolescents don’t have all of their teeth so they should have a diet of soft foods to avoid choking Delivering Nutrients to Body Cells Nutrients absorbed into the mucosal cells of the intestine enter the blood circulation by the hepatic portal circulation of the lymphatic system. The liver stores nutrients (like glucose in the form of glycogen) if there’s room It can store about 300 to 400 calories of glycogen Another 1,500 calories can be stored in the muscles The liver breaks down the excess molecules so that they can be sent to other parts of the body The liver can sense blood sugar levels, so it can secrete glucose Lymphatic system can allow large molecules (like fat) to be transported throughout the body The Mitochondrion and Energy Metabolism Metabolic reactions are a series of reactions need to transform food Types of metabolic reactions Catabolic reactions-breaking down molecules Anabolic reactions-builds/combines molecules Catabolic reactions release energy trapped in the chemical bonds that hold molecules together Some of this energy is lost as heat, but some is used to create ATP (aka energy currency) There are high energy bonds within the phosphate group of ATP Producing ATP Without oxygen, only glucose is used to produce ATP When oxygen is available, glucose, fatty acids, and amino acids can be broken down to yield two-carbon units that form a molecule called acetyl- CoA To form acetyl-CoA from glucose, it is first split in half by glycolysis in the cytosol To form acetyl-CoA from fatty acids, the carbon chains that make up fatty acids are broken down by beta-oxidation in the mitochondria To from acetyl-CoA from amino acids, an amino acid is removed by deamination in the mitochondria Elimination of waste Substances in food that cannot be absorbed are eliminated in the feces. Wastes generated from nutrient metabolism, called metabolic wastes, are eliminated from the body by the integumentary (skin), urinary, and respiratory system Carbon dioxide produced by cellular respiration leaves the cells through the respiratory and cardiovascular system Excess nutrients are lost by the digestive system Other waste products are lost by the urinary system Celiac Disease What is Celiac Disease? It is common It is an autoimmune disorder when the mucosal cells and microvilli are being attacked by immune cells when it is around gluten What are the symptoms? Decreased function of the small intestine Skin rash Weight loss Deficient in iron or other vitamins and minerals What foods to avoid? Wheat or to the stuff with gluten-they can NEVER eat gluten Is there a difference between celiac, gluten insensitivity and a wheat allergy? Celiac disease and wheat allergy can possibly considered the same A wheat sensitivity is different because of the level of severity is different Chapter 4 Sugars, Starches, and Fiber Carbohydrates in the modern diet Foods that are high in carbs are the basis of our diet. The AMDR for carb is 45-65% . Americans typically consume 50% calories for carbs. In our country, our carb diet comes from refined carb. There is 4 kcal per gram for carb which is equal to protein. Although they equal, our bodies process refined carbs into fat quickly (from a high response). The body is not able to process and store the calories from fat as well as they can for protein Provide a wide variety of nutrients needed for health when consumed in “whole food” form Sources of Carbs Grains, vegetables, legumes, fruits, nuts, seeds, and milk are all sources of carbs A raw carrot has less carb vs. cooked carrot since it becomes more of a starch. Peas are also considered a starch. Fiber in fresh fruits slows down our ability to digest food and the hormonal response of insulin secretion (insulin promotes storage). Corn and sugarcane are unrefined sources of carb, but the corn in cornflakes and sugar in table sugar has been processed by grinding, cooking, and extruding, and drying. These refined products are missing some of the fiber and other nutrients present from the original Our countries struggles with weight because of the increase in processing (like in cereals). The refined version of sugar cane is high fructose corn syrup. It is used because it is stable and it has a high storage life Whole grains The outermost bran layers of a kernel of grain contain most of the fiber and are a good source of vitamins The germ, which lies at the base of the kernel, is the plant embryo where sprouting occurs. It is a source of some vegetable oils and it is rich in vitamin E. It also contains protein fiber, and B vitamins riboflavin, thiamin, and vitamin B6 The remainder of the kernel is the endosperm, which is primarily starch but also contains most of the protein and some vitamins and minerals. During the milling process, the grinding detaches the germ and bran from the endosperm White flour is produced just from the endosperm Fiber and some vitamins are lost during the milling process To restore some of the nutrients lost in, refined grains sold in the US are enriched with some of the nutrients lost Whole grains vs. Refined Grains Refined refers to foods that have undergone processing that removes various components of the original food Pasta, breads are usually enriched foods that are refined is when a nutrients are removed during processing and then some of the nutrients are added back. Fortified foods are orange juice or proactive yogurt which means that a random nutrient that gets added. Nutrients that would be lacking in enriched bread: magnesium, fiber, vitamin b6, vitamin E and many others High Fructose Corn Syrup and Obesity The increase in use of high fructose corn syrup has contributed to the increase in obesity. Fructose comes from sucrose (table sugar) Refined sugars added to foods are not nutritionally or chemically different from sugars occurring naturally in foods. The only difference is that they have be separated from their plant sources and therefore are not consumed with all of the fiber, vitamins, minerals and other substances found in the original plant. Because refined sugars provide few nutrients for the number of calories they contain, they have a low nutrient density and are considered empty calories. Kiwis are a more nutrient-dense snack than red licorice. Although 3 kiwis provide about the same number of calories as four pieces of licorice, the kiwis are an unrefined source of sugar that also provides fiber, vitamin C, folate and calcium. Most of the calories in the licorice are from added refined sugars and contains less nutrients Types of Carbs Simple carbs-a class of carbs, known as sugars, that include monosaccharides and disaccharides Ex. Of monosaccharides: glucose (this circulates in blood), fructose (found in fruits, vegetables, honey and high fructose corn syrup), galactose (is milk sugar) Ex. Of disaccharides: maltose (it is made up of 2 glucose units), sucrose (it is made up of glucose and fructose-table sugar), lactose (it is made up of glucose and galactose) Complex carbs-are composed of sugar molecules linked together in straight or branching chains They include oligosaccharides (3-10 sugar units) and polysaccharides (a carbohydrate made up of many sugar units) Examples of polysaccharides are: glycogen (a polysaccharide made up of many molecules of glucose-the storage form of carb in animals), starch (made up of many molecules-the storage form of carb in plants), fiber (a mixture of indigestible carbs and lignin that is found in plants) Making and Breaking Sugar Chains In the dehydration reaction, 2 glucose molecules are joined to form the disaccharide maltose and a molecule of water. In the hydrolysis reaction, the addition of a molecule of water breaks maltose into its component glucose molecules Dietary Fiber Fiber is NOT digested but it helps with the growth of beneficial intestinal microbiota (in large intestine) and inhibit the growth of undesirable bacteria Whole grains, legumes, fruits, and vegetables are good sources of soluble and/or insoluble fiber Soluble fiber is soft and dissolves in the digestive tract and produces a gel in the intestines and this gel removes cholesterol from the bloodstream Insoluble fiber as a hard structure (roughage); it provides more stuff to keep things moving in the right direction but it needs water Fibers can be added to processed foods to thicken them and reduce fat and calories We need both types of fiber (25-30 grams of total fiber everyday) Americans usually get ~13 grams of fiber Dietary fiber cont’d Food sources of soluble fiber: Legumes Prunes Apricots Raisins Oranges Bananas Oats Apples Eggplants Flaxseed Food sources of insoluble fiber Wheat bran Whole wheat bread Broccoli Eggplant Apple skins Nuts and seeds Carbohydrate Digestion and Absorption The process of carb digestion begins in the mouth and continues throughout the GI tract. Enzymes break starches and sugars into monosaccharides, which are absorbed. Most of the fiber is excreted in the feces Carbs are NOT digested in the stomach Fiber can be partially broken down by the bacteria in the large intestine, which causes gas Lactose Intolerance It is a condition in which symptoms including abdominal distention, flatulence, cramping, and diarrhea develop after the consumption of dairy products It occurs when there is not enough of the enzyme lactase in the small intestine to digest the lactose When people with lactose intolerance consume dairy products, the lactose passes into the large intestine, where it is quickly metabolized and this cause gas Fiber in the Digestive Tract Fiber increases the weight of material in the lumen of the intestine. The extra weight is due to the bulk of the fiber itself, the water held by the fiber, and the increase in the number of bacteria. The result is a larger, softer stool, which promotes healthy bowel function by stimulating peristalsis. More peristalsis causes the muscles of the colon to work more, become stronger, and function better Helps to ease evacuation Prevents constipation Intestinal microbiotia They are the microscopic bacteria that make up the large intestine They break down fiber when it reaches the colon When this happens, short chain fatty acids, which serve as a fuel source for cells in the colon and are absorbed into the bloodstream where they provide energy to other body cells The short-chain fatty acid also make colonic contents more acidic, which inhibits the growth of undesirable bacteria
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