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Chapter 16 Food and Digestion Section 1 Food and Energy Objective: List and describe each of the six nutrients needed by the body Why You Need Food Food provides: Materials for growing Materials to repair tissues Energy The ability to maintain homeostasis Why You Need Food Food is converted into nutrients Nutrients = the substances in food that provide the raw materials and energy the body needs to carry out all the essential processes Why You Need Food 6 necessary nutrients; 1. 2. 3. 4. 5. 6. Carbohydrates Fats Proteins Vitamins Minerals water Why You Need Food The amount of energy needed to raise the temperature of one gram of water by one oC = calorie (lowercase c) The measure of the amount of energy in food = Calorie (capital C) 1 C = 1,000 c Carbohydrates Major energy source Provide raw materials to make cell parts 2 groups: Simple carbohydrates Complex carbohydrates Simple Carbohydrates Aka sugars Naturally found in: Fruits Milk Some vegetables The major source of energy = glucose Complex Carbohydrates Many sugar molecules linked in a long chain Ex: starch Found in potatoes, rice, corn, pasta, cereals, and bread The long chains must be broken to get energy from the sugar molecules Complex Carbohydrates Fiber: Complex carbohydrate found in plants Cannot be broken down Not considered a nutrient Keeps your digestive system working properly Complex Carbohydrates 50% - 60% of your daily Calories should come from carbohydrates Complex carbohydrates are recommended because they provide a more even, long-term energy source Fats High-energy nutrient Make up part of cell structures Fatty tissue protects and supports internal organs Insulates your body to keep heat inside your body HOWEVER; has twice as much energy as the same amount of carbohydrates! 2 groups: Unsaturated fats Saturated fats Fats Unsaturated Liquid at room temperature Cooking oils Saturated Fats: Fats Solid at room temperature Meat, dairy, egg yolk Fats Cholesterol < Waxy, fatlike substance found only in animal products Your liver makes all the cholesterol your body needs Cholesterol is not necessary in your diet 30% of your diet should come from fats Proteins Needed for tissue growth and repair Play a part in chemical reactions in cells (enzymes) Energy source (less than carbs & fats) Found in meat, poultry, fish, dairy products, nuts, beans, lentils ~12% of your diet should come from protein Proteins The building blocks of proteins = amino acids Only 20 different amino acids Half of the amino acids you need can be made by your body The others must come from your diet = essential amino acids Proteins Complete proteins: Contain all the essential amino acids Sources: meat, eggs Incomplete proteins: Missing 1 or more essential amino acids Sources: beans, grains, nuts Vitamins Helper molecules in a variety of chemical reactions within the body = vitamins If you eat a wide variety of foods, you will probably get enough of each vitamin Minerals Nutrients not made by living things = minerals Source: plant foods, or eating animals that eat plants Ex: Calcium for strong bones Iron for red blood cells Water Chemical reactions take place in water Makes up most of the body’s fluids Nutrients dissolve in water to be carried throughout your body Section 2: The Digestive Process Begins Objectives: Describe the general functions carried out by the digestive system and the specific functions of the mouth, esophagus, and stomach Functions of the Digestive System 3 main functions: 1. 2. 3. Breaks food down into molecules the body can use The molecules get carried throughout the body by the blood Eliminates wastes from the body Functions of the Digestive System The process by which your body breaks down food into small nutrient molecules = digestion Mechanical digestion = food is broken into smaller pieces Chemical digestion = chemicals break food into their smaller chemical building blocks The process by which nutrient molecules pass through the wall of your digestive system and into your blood = absorption The Mouth The fluid released when your mouth waters = saliva Both mechanical and chemical digestion begin in the mouth Teeth grind food Enzymes in saliva begin breaking down food The Esophagus The muscular tube that connects the mouth and the stomach = esophagus Flap of tissue that prevents food from entering the windpipe = epiglottis A thick, slippery substance that makes food easier to swallow and move through the esophagus = mucus Muscle contractions that push food toward the stomach = peristalsis The Stomach Expands to hold all the food you swallow Mechanical and chemical digestion occur here Has an enzyme that breaks down protein = pepsin And a very strong acid = hydrochloric acid ASSIGNMENT Section Pg. Review Questions 523 #’s 1-4 WRITE QUESTIONS AND ANSWERS Section 3: Final Digestion and Absorption Objectives: To explain the role of the small intestine in digestion To explain the role of the large intestine in digestion The Small Intestine Almost all chemical digestion and absorption takes place in the small intestine The Role of the Liver Breaks down medicines and other substances Removes nitrogen from the body Produces bile Substance that breaks up fat particles = bile Gallbladder- stores bile Bile leaves gallbladder and enters small intestine after you eat Help From the Pancreas Lies between stomach and small intestine Produces enzymes that break down starches, proteins, and fats Absorption in the Small Intestine Villi = tiny finger-shaped structures The villi absorb nutrients Nutrients then enter blood vessels The Large Intestine The Last section of the digestive system Contain bacteria the feed on passing material As material moves through the large intestine, water is absorbed into the bloodstream The remaining material is readied for elimination ASSIGNMENT Section Pg. Review Questions 529 #’s 1-3 WRITE QUESTIONS AND ANSWERS!
