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Unit 1: Animals : Structure and Function Chapter 10: The Digestive System Nutrition Obtaining and Processing Food All organisms, regardless of their size or complexity, must have a way of obtaining essential nutrients Essential nutrients: the basic raw materials they need to make their own structures, perform their life functions, and obtain energy for survival Macromolecules Organic molecules contain carbon bonded to hydrogen, as well as to other atoms, such as oxygen, sulfur, and nitrogen. Macromolecules are larger, more complex assemblies of organic molecules, also known as nutrients. These are the raw materials that our bodies need to provide energy, to regulate cellular activities, and to build and repair tissues. Often grouped into four major categories: ◦ Carbohydrates ◦ Lipids ◦ Proteins ◦ Nucleic acids Macromolecules Energy released from these macromolecules, and matter supplied by them, is used to maintain the body’s metabolism (all of the chemical processes carried out by cells to maintain life) Together, the four major categories of macromolecules are known as essential nutrients. Carbohydrates Are macromolecules that always contain carbon, hydrogen, and oxygen ◦ Almost always in the same proportion: ◦ C1 : H2 : 01. Provide short-term or longterm energy storage for organisms. There are two main types of carbohydrates: simple sugars and polysaccharides. Monosaccharides (Simple Sugars) Carbohydrate molecules with three to seven carbon atoms. ◦ Examples: glucose (the sugar found in blood) and fructose (the sugar found in fruit). Disaccharides Made up of two simple sugars (di- = two). ◦ Examples: sucrose (table sugar), lactose (the sugar found in dairy products) and maltose (the sugar found in germinating grain) Polysaccharides Complex carbohydrates that consist of many linked simple sugars (poly- = many). ◦ Examples: Starch stores energy in plants, and glycogen stores energy in animals. Carbohydrates Lipids Are insoluble in water. The basic structure of lipids is a molecule of glycerol ◦ 3 carbon atoms, each attached to a fatty acid chain Store 2.25 times more energy per gram than other biological molecules; function as energystorage molecules. Lipids Phospholipids, form cell membranes. Other Examples of lipids are fats, such as butter and lard, and oils, such as olive oil and safflower oil. Proteins Assembled from small sub-units known as amino acids Polypeptides are chains for hundreds of amino acids joined together by peptide bonds Most enzymes are proteins, and so are antibodies, which combat disease. Proteins help build and repair muscles and cell membranes Nucleic Acids Nucleic acids direct growth and development of all organisms using a chemical code. The two types of nucleic acids are ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Hydrolysis From Greek: “Hydro” – water; “lysis” – loosen A water molecule (H2O) is added to the macromolecule. This breaks the chemical bonds that hold together the smaller molecules from which the macromolecule is made. Digestive enzymes help to speed up the process of hydrolysis. Minerals and Vitamins Inorganic and organic substances that enable chemical reactions to occur and aid in tissue development, growth, and immunity. Needed by a healthy, functional human body. Minerals Mineral Key function in the body Possible Sources Calcium Forming bone, conducting nerve signals, contracting muscle, clotting blood Dairy products Iron Producing hemoglobin Red meat Magnesium Supporting enzyme functions, producing Dark, leafy greens protein Potassium Conducting nerve signals, contracting muscle Grains Sodium Conducting nerve signals, balancing body fluids Salt Vitamins Vitamin Key function in the body Possible Sources A (carotene) Good vision, healthy skin and bones Fruits B1 (thiamine) Metabolizing carbohydrates, growth and muscle tone Beans C (ascorbic acid) Boosting immune system, healthy bones, teeth, gums, and blood vessels Fruit D Absorbing calcium, forming bone Fish E Strengthening red blood cell membranes Fruit Water Needed for the proper functioning of all cells and organs. Makes up 2/3 of body mass. Functions include: ◦ Transporting dissolved nutrients into the cells that line the small intestine ◦ Flushing toxins from cells ◦ Lubricating tissues and joints ◦ Forming essential body fluids, such as blood and mucus ◦ Regulating body temperature (by sweating) ◦ Eliminating waste materials (in urine and sweat) Learning Check Pg 406, Q 1-6: 1) What is the the primary function of carbohydrates in the human body? 2) What is the difference between a monosaccharide and a disaccharide? Given an example of each. 3) Explain how macromolecules are broken down in the body Learning Check Pg 406, Q 1-6: 4) If an athlete runs for 15 minutes, which macromolecules are likely to break down first? 5) Which macromolecules would provide the greatest benefit as a long-term energy storage molecule to a bird that migrates long distances? 6) Name the three functions of proteins in the human body. Types of Digestion Intracellular digestion: Extracellular digestion: ◦ Digestion inside the cell ◦ Phagocytosis - cell engulfs the food Ex: single-celled organisms (paramecium, amoeba) ◦ Digestion outside the cells ◦ Food enters a tube and exits from the other end Ex: most animals, human digestive tract Mechanical Digestion The physical breakdown of large food particles into smaller ones. ◦ Achieved through chewing, mashing, chopping, breaking food into smaller pieces. ◦ This increases the surface area of the food, allowing more enzymes to come into contact with the food. Chemical Digestion The chemical breakdown of large molecules into smaller ones: ◦ Carbohydrates: polysaccharides (starch) are broken into monosaccharides (simple sugars) ◦ Proteins: are broken down into amino acids ◦ Lipids: (mainly triglycerides) are broken down into fatty acids and glycerol Note: Food particles are broken down by enzymes. Each enzyme has a pH at which it performs best. Types of Feeders Autotrophs: ◦ Can feed themselves from inorganic molecules ◦ Ex: plants use sun + H2O + CO2 to form organic compounds ◦ Self-sufficient Heterotrophs: ◦ Depend on organic compounds made by other living things ◦ Ex: animals, fungi, bacteria, etc. ◦ Not self-sufficient Filter Feeders Aquatic animals that use a body structure similar to a filter basket to gather small organisms suspended in the water. Siphons water into its mouth and then filters it to obtain small organisms to digest. Examples include flamingoes, tube worms, clams, barnacles, and baleen whales. Fluid Feeders Obtain food by sucking or licking nutrient-rich fluids from live plants or animals. Mouth parts are adapted to pierce or rip skin or leaf tissue and are used to suck or lick the blood or sap that is their food. Examples: mosquitoes, ticks, aphids, spiders, bees, butterflies, vampire bats, and hummingbirds. Substrate Feeders Live in or on their food source and eat their way through it. Examples: caterpillars and earthworms. Caterpillars eat their way through the green tissues of leaves. Bulk Feeders Include many animals and most vertebrates (including humans). Bulk feeders ingest fairly large pieces of food and some, like the great blue heron, swallow their food whole. Use tentacles, pincers, claws, fangs, or jaws and teeth to kill prey, to tear off pieces of meat or vegetation, or to take in mouthfuls of animal or plant food. The Digestive System Introduction There are four stages to food processing: 1. Ingestion: taking in food 2. Digestion: breaking down food into nutrients 3. Absorption: taking in nutrients by cells 4. Egestion: removing any leftover wastes Digestion and the Alimentary Canal Length of the Digestive Tract Cellulose walls in plant tissue are more difficult to digest than animal tissues As a result, whose digestive tracts would be longer? Herbivores/omnivores OR carnivores? Section 10.1 Review Pg 410 # 1-3, 6-9, 11 10.2 Introduction The digestive system is used for breaking down food into nutrients which then pass into the circulatory system and are taken to where they are needed in the body. Human Digestive System Begins when food enters the mouth (oral cavity). It is physically broken down by the teeth (mechanical). It is chemically broken down by enzymes released from the salivary glands. Human Digestive System The tongue moves the food around until it forms a ball called a bolus. The bolus is passed to the pharynx (throat) and the epiglottis makes sure the bolus passes into the esophagus and not down the trachea! Human Digestive System What structure prevents food from entering the nasal passageway? How? Human Digestive System The bolus passes down the esophagus by peristalsis. Peristalsis is a wave of muscular contractions that push the bolus down towards the stomach. Human Digestive System To enter the stomach, the bolus must pass through the lower esophageal sphincter, a tight muscle that keeps stomach acid out of the esophagus. Human Digestive System The stomach has folds called rugae and is a big muscular pouch which churns the bolus (physical digestion). The bolus is mixed with gastric juice, a mixture of stomach acid and enzymes (chemical digestion). Human Digestive System The stomach does do some absorption too. Some medicines (i.e. aspirin), water and alcohol are all absorbed through the stomach. The digested bolus is now called chyme and it leaves the stomach by passing through the pyloric sphincter. Learning Check Pg 414, Q 7, 9, 11,12 7) Describe where the digestion of carbohydrates begins in the body, the major glands involved, and the digestive secretions produced. 9) Would the epiglottis be closed or open in each situation? Explain: ◦ A) while talking ◦ C) coughing B) swallowing D) chewing Learning Check 11) A doctor orders a pH test of the esophagus for patient who is complaining about having heartburn and a burning sensation in the chest. Identify the source of the problem and explain why. 12) How do over-the-counter antacids (eg. Calcium carbonate) help an individual with stomach pain/gastroesophageal discomfort? Stages of Digestion http://video.about.com/ibdcrohns/Digestion. htm Human Digestive System Chyme is now in the small intestine. The majority of absorption occurs here. The liver and pancreas help the small intestine to maximize absorption. The small intestine is broken down into three parts: Human Digestive System 1. Duodenum Bile enters through the bile duct. It emulsifies fats. The pancreas secretes pancreatic juice containing enzymes and bicarbonate ions Human Digestive System 2. Jejunum The jejunum is where the majority of absorption takes place. It has tiny fingerlike projections called villi lining it, which increase the surface area for absorbing nutrients. Human Digestive System Each villi itself has tiny fingerlike projections called microvilli, which further increase the surface area for absorption. Human Digestive System 3. Ileum The last portion of the small intestine is the ileum, which has fewer villi and basically compacts the leftovers to pass through the caecum into the large intestine. Human Digestive System The large intestine (or colon) is used to absorb water from the waste material leftover and to produce vitamin K and some B vitamins using the helpful bacteria that live here. Human Digestive System All leftover waste is compacted and stored at the end of the large intestine called the rectum. Pressure receptors are stimulated and send a signal to the brain to indicate that elimination is necessary. The anal sphincter remains under voluntary control. Feces, passes out of the body through the anus. Chemical Digestion Introduction Food cannot be broken down into small enough nutrients by physical digestion alone. Special enzymes in our body help chemically break down food into small nutrients. Magic School Bus – “For Lunch” http://www.peteava.ro/id-538489-02-forlunch Enzymes Enzymes are special proteins made at ribosomes. There are different classes of enzymes: 1. Carbohydrases break down carbs 2. Proteases break down proteins 3. Lipases break down lipids. Enzymes These enzymes are secreted into the digestive system by special groups of secretory cells called glands. Glands are usually connected to the digestive system through special tubes called ducts. Enzymes The item that an enzyme breaks down is called a substrate. The enzyme is not changed at all during this process. Every enzyme performs best under its own optimal conditions. This depends on temperature, pH and the presence/absence of certain ions or vitamins and minerals. The Mouth Three salivary glands produce saliva which contains: ◦ Water and mucous: lubricates the food ◦ Sodium bicarbonate: reduces the acidity of the bolus ◦ Salivary amylase: enzyme that begins to break down carbohydrates (amylose) The Stomach Hydrochloric acid (HCl) kills off any invading bacteria or viruses and is very corrosive. The enzyme pepsin breaks down proteins. It is only active at a low pH. The enzyme lipase breaks down lipids. Mucus protects the lining of the stomach from being eaten away by the acid. The Pancreas Produces and releases into the small intestine: ◦ Enzymes that act on proteins, carbohydrates, and fats. ◦ Bicarbonate ions to raise the pH of the chyme. Produces and releases into the blood stream: ◦ Insulin that converts glucose to glycogen, which gets stored in the body cells for later use. Enzymes Video: Amylases, proteases and lipases http://video.about.com/nutrition/Enzymes -and-Digestion.htm http://www.youtube.com/watch?feature= endscreen&NR=1&v=KED6BHVM97s The Liver Makes bile, which aids in fat digestion Most of the glycogen is stored here Vitamins A, D, E, K are stored here Detoxifies poisons that are ingested (including ethanol) ◦ Cirrhosis: breakdown of liver cells due to high levels of poisons. The Gall Bladder Stores the bile produced in the liver. Releases bile into the small intestine. Illnesses of the gall bladder include ◦ Gall stones: crystals of bile salts around cholesterol. ◦ Jaundice: collection of bile pigment in blood. Liver and Pancreas http://www.youtube.com/watch?v=TWUZ x738OZM&feature=related Overview of Human Digestion http://www.youtube.com/watch?v=08VyJ OEcDos&feature=related Digestion and Homeostasis A large meal activates receptors that churn the stomach and empty it faster. If the meal was high in fat, digestion is slowed, allowing time for the fat to be broken down. Hence why we feel fuller after eating a high fat meal. Digestion and Homeostasis The endocrine, nervous, digestive and circulatory systems all work together to control digestion. Before we eat, smelling food releases saliva in our mouths and gastrin in our stomachs which prepares the body for a snack. The Hormone Gastrin Hormones Hormones are chemical regulators, they also help control digestive enzymes. The hormone gastrin stimulates the digestive glands around the stomach. The hormone secretin stimulates the pancreas to release its enzymes which help neutralize the stomach contents as they enter the small intestine. Pg 417 13-18 Learning Check HW pg 419 # 1, 11-13, 15