Chapter 3 and 4 Outline
Chapter 3 and 4 Outline BIO 140
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This 9 page Study Guide was uploaded by Chase Huber on Tuesday February 17, 2015. The Study Guide belongs to BIO 140 at Washington State University taught by Bethany Marshall in Spring2015. Since its upload, it has received 135 views. For similar materials see Nutrition in Biology at Washington State University.
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Date Created: 02/17/15
Nutrition Test 2 Notes 02182015 Chapter 3 Digestion From Meals to Molecules 31 The Organization of Life Everything is made of atoms atoms form to create molecules the molecules are organized into cells Cells are the smallest unit of life Cells that are similar in function form tissues Human body contains four types of tissues Muscle nerve epithelial and connective These tissues are organized in varying combinations to form organs An organ functions as part of an organ system The bodies 11 organ systems work together to perform all functions necessary for life Hormones A chemical Messenger that is produced in one location in the body it is released into the blood and sent to other systems to elicit responses 32 The Digestive System The digestive system is the organ system that is primarily responsible for digestion and for the absorption of nutrients into the body Proteins must be broken down into amino acids Carbohydrates are broken down into sugars Most fats are digested to produce molecules known as Fatty Acids The sugars amino acids and fatty acids can then be absorbed into the body The ber in fruits whole grains etc cannot be broken down and therefore passes through the digestive tract and is eliminated through feces Organs of the Digestive system The digestive system is composed of the gastrointestinal tract and accessory organs 0 A hollow tube that runs from the mouth to the anus 0 Also known as Digestive tract 0 The organs that compose the Digestive Tract are Mouth Chews and mixes food with saliva Pharynx Swallows chewed food Esophagus Moves Food to the Stomach Stomach Churns and mixes food secretes acid and protein digesting enzyme Small Intestine Complete digestion absorbs nutrients into blood 0 Large Intestine Absorbs water and some minerals home to intestinal bacteria passes waste material Anus Opens to allow waste to leave body 0 Accessory Organs Salivary Glands Produce Saliva Liver Makes Bile which aids in digestion and absorption of fat Pancreas Releases bicarbonate to neutralize intestinal contents produces enzymes that digest carbs fats and proteins Gallbladder Stores bile and releases it into the small intestine when needed 0 The inside of the digestive tract is called the lumen 0 Food inside the lumen is not technically inside the body because it has not been absorbed The Lumen is lined with a layer of mucosal cells called mucosa 0 Because mucosa cells are in direct contact with food they only live about 2 to 5 days The dead cells are sloughed off into the lumen Mucosa must be replaced quickly and is one of the rst places to experience nutrient de ciencies The length of time it takes food to go from mouth to anus is called the transit time o The shorter the transit time the more rapidly material is passing through the digestive tract Digestive System Secretions O 0000 O Digestion is aided by substances secreted into the digestive tract 0 One of these substances is mucus which moistens lubricates and protects cells from harsh environments Enzymes are also present in digestive system secretions and they accelerate chemical reactions and help breakdown food Enzymes are specialized o Amylase Breaks down large carbohydrate molecules 0 Lipases Digest Fat 33 Digestion and Absorption of Nutrients Digestive tract can be activated by sensory input alone The Mouth Digestion involves chemical and mechanical processes both of which begin in the mouth 0 The presence of food in the mouth stimulates ow of saliva from the salivary glands Saliva moistens food and carries dissolved food molecules to the taste buds Saliva contains the enzyme Salivary Amylase which begins the chemical digestion of food by breaking starch molecules into shorter sugar chains 0 Chewing begins the mechanical aspect of digestion Chewing breaks up ber which can trap essential nutrients if this does not happen these nutrients will be lost The Pharynx The pharynx the part of the Gastrointestinal tract that is responsible for swallowing is also part of the respiratory tract 0 During swallowing the air passages are blocked by a valve like tissue called the epiglottis so that food goes to the esophagus and notthelungs 0 Sometimes fast eating can cause food to enter air tube this can be removed by coughing or forced out by using the Heimlich The Esophagus The Esophagus connects the pharynx with the stomach In the esophagus the bolus of food is moved along the smooth muscles called peristalsis These contractions are strong enough to make food reach your stomach if you were standing on your head 0 To move from the esophagus and enter the stomach food must pass through a sphincter a muscle that encircles the tube of the digestive tract and acts as a valve When it contracts the valve closes when it relaxes the valve opens allowing food to pass The sphincter prevents food from moving back up the esophagus Food that moves back up the esophagus past the sphincter causes heartburn The Stomach The stomach serves as a temporary storage place for food Here the food bolus is mixed with highly acidic stomach secretions to form a semiliquified food mass called chime Very little absorption occurs in the stomach Gastric Juice is produced by gastric glands in pits that dot the stomach lining promotes chemical digestion in the stomach Small Intestine The small intestine is a narrow tube about 20 feet long Here the chime is propelled along by peristalsis and mixed rhythmic contractions called segmentation that slosh the material back and forth The small intestine is the main site for chemical digestion of food completing the process the mouth and stomach have started 0 It is also the site for absorption of water vitamins minerals etc Secretions Aid Digestion o Secretions from the pancreas gallbladder and small intestine aid digestion o The pancreas secretes pancreatic juice Which contains bicarbonate and digestive enzymes 0 Pancreatic Amylase is an enzyme that continues the job of breaking down starches into sugars o Pancreatic Proteases break down protein into shorter and shorter chains of amino acids 0 Fat digesting enzymes called lipases break down fats into fatty acids 0 The Gallbladder stores and secretes bile a uid containing bile acids and cholesterol which is produced in the liver and is necessary for the digestion and absorption of fat 0 Absorption In order for foods to be absorbed nutrients must pass from the lumen of the GI tract into the mucosal cells lining the tract then into the blood or the lymph Diffusion the net movement of substances from an area of high concentration to low concentration Osmosis diffusion of water Facilitated Diffusion a carrier molecule is needed to carry a substance across the cell membrane Active Transport Requires energy and a carrier molecule 34 Digestion in Health and Disease The Digestive System and Disease Prevention If an invading substance or antigen enters the lumen or is absorbed into the mucosa the immune system can use a number of weapons to destroy it 0 When an antigen is present Phagocytes are the rst type of white blood cell to come to the body s defense 0 If Phagocytes do not eliminate the invade white blood cells lymphocytes which target speci c antigens enter the battle 0 These white blood cells produce protein molecules called antibodies which bind to antigens and destroy them 0 An allergic reaction occurs when the immune system produces antibodies in response to an allergen o Celiac Disease A condition in which the protein gluten in wheat etc triggers and immune system response that destroys the villi of the small intestine Digestive system Problems and Discomforts Heartburn occurs when the acidic contents of the stomach leak back into the esophagus Occational heartburn is ne but if it happens often it is called GERD Eating smaller meals can help reduce heartburn Peptic Ulcers occur when the mucus barrier protecting the stomach is penetrated and the acid leaks into the digestive systems and damage the GI lining Gallstones clumps of solid material that accumulate in the gallbladder or bile duct 35 Delivering Nutrients and Eliminating Wastes The Cardiovascular System The cardiovascular system delivers the nutrients absorbed from the digestive system to other parts of the body It circulates blood throughout the body which carries oxygen and nutrients everywhere 0 The heart is the workhorse The blood vessels that transport blood and nutrients towards the heart are called veins and the arteries take blood and nutrients away from the heart 36 An Overview of Metabolism the chemical reactions that break down molecules to provide energy and those that synthesize larger molecules are referred to as metabolism Mitochondria specialize in breaking down molecules to release energy and ribosomes synthesize proteins 0 Cellular respiration oxygen goes into the cell and carbon dioxide comes out The energy released during cellular respiration is called ATP and can be though of the cell energy currency Chapter 4 Carbohydrates Sugars Starches and Fibers 41 Carbohydrates in our Foods Our ancestors ate entirely unre ned foods foods eaten as they are in nature or with minimal processing Many of the foods we eat today are re ned grains and contain added re ned sugar 0 The increase of re ned grains has been a leading cause of obesity around the world What is a Whole Grain A whole grain product whole wheat bread or oatmeal grain products that contain the entire kernel of the grain the germ the bran and the endosperm Re ned grains contain just the endosperm the bran and the germ are discarded during re ning To make up for the loss in nutrients re ned grains are required to be enriched with added nutrients What is Added Re ned Sugar Re ned sugars account for almost 15 of the calories consumed in the typical American diet 0 They do not contain the ber vitamins and minerals found in the original plant and are considered empty calories 42 Types of Carbohydrates Chemically Carbohydrates are a group of compounds made up of one or more sugar units that contain carbon 0 Carbs made of only one sugar unit are called monosacharides those made with two sugars are called disaccharides and those made of more are called polysaccharides Simple Carbohydrates Monosaccharaides and Disaccharides are classi ed as simple carbohydrates and are what we commonly refer to as sugars o The three most common monosaccharaides in the diet are glucose fructose and galactose The most common disaccharides in our diet are maltose sucrose and lactose Complex Carbohydrates Complex Carbs are polysaccharides and are generally not sweet tasting the way simple carbs are They include glycogen in animals and starches and bers in plants 43 Carbohydrate Digestion and Absorption Carbohydrate Digestion Carbohydrate digestion begins in the mouth but most starch digestion and breakdown of disaccharides occurs in the small intestine Carbs that cannot be digested pass into the colon Lactose Intolerance The disaccharide lactose is broken down by the enzyme lactase in the small intestine In some people levels of lactase decline with age and thus lactose cannot be entirely digested Lactose then passes into the large intestine where it mixes with water and produces gas lndigestible Carbohydrates Some carbs are not digested and therefore are not readily absorbed Fiber and some oligosaccharides cannot be broken down by human enzymes Resistant Starch isn t digested either because the natural structure of the grain products Carbohydrate Absoprtion After a meal the monosaccharide s from carb digestion enter the portal circulation and travel to the liver Glucose provides energy stored as glycogen in the liver or delivered to other systems through blood circulation o Glycemic Response is the measure of the impact a food has on blood glucose levels 0 Re ned sugars and starches generally cause a greater glycemic response then unre ned carbs because sugars and starches consumed alone leave the stomach quickly and are rapidly digested 44 Carbohydrate Functions The main function of carbs is to provide energy but they can also play other roles in the body For example nerve tissue needs the sugar galactose and in breast feeding women glucose combines with galactose to produce milk sugar lactose Getting Enough Glucose to Cells Glucose is an important fuel for body cells 0 Brain cells red blood cells must have glucose to stay alive 0 The concentration of glucose in the blood is regulated by the liver and by hormones secreted by the pancreas o The rise in glucose levels after eating stimulates the pancreas to secrete the hormone insulin which allows glucose to enter muscle and fat cells thereby lowering the level of glucose in the blood 0 After a few hours after eating blood glucose levels drop enough to trigger the pancreas to secrete the hormone glucagon which raises blood glucose levels by signaling liver cells to break down glycogen into glucose which is released into the blood At the same time the liver begins to synthesize new glucose molecules which are also released into the blood bringing levels back to normal Glucose as a Source Of Energy Cells use glucose to provide energy via cellular respiration Cellular respiration uses oxygen to convert glucose to carbon dioxide and water and provide energy in the form of ATP 0 The rst step in cellular respiration is glycosis which creates two molecules of ATP from each glucose molecule Oxygen is not needed so it is often considered an anaerobic metabolism 0 When oxygen is available the complete breakdown of glucose can proceed This Aerobic Metabolism produces 36 molecules of ATP for each glucose molecule 18 times more ATP than is created by anaerobic metabolism What happens when Carbohydrate is Limited Limited Carbohydrate increase protein breakdown 0 Amino acids can be used to help recreate glucose molecules 0 This takes them away from other body proteins 0 A carb is said to spare proteins Limited Carbohydrate interferes with fat breakdown 0 When carbs are in short supply molecules cannot proceed with aerobic metabolism and therefore form ketones or ketone bodies Ketones can be used to replace glucose for a short time but can cause ketosis which causes headaches and can lead to death 45 Carbohydrates in Health and Disease Diabetes 0 A disease characterized by high glucose blood levels Damages heart kidneys eyes etc 0 Leading cause of adult blindness 0 Type 1 Diabetes Autoimmune disease in which insulin secreting pancreatic cells are destroyed by the immune system People with type 1 diabetes must inject insulin to keep blood glucose levels in normal range 0 Type 2 diabetes occurs when the body doesn t produce enough insulin to keep glucose within normal ranges This occurs because body cells lose their sensitivity to insulin known as insulin resistance Hypoglycemia Abnormally low blood glucose levels 0 Occurs most frequently in people who have diabetes as a result of overmedication It is caused by abnormalities of insulin production or how the body responds to insulin Fasting Hypoglycemia occurs when an individual has not eaten Dental Caries 0 Cavities Occur when bacteria form colonies called plaque on the tooth surface Weight management 0 Heart Disease 0 There is evidence that diets high in sugar can raise blood lipid levels and increase risk of heart disease
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