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. Carbohydrates 2. Fats 3. Proteins 4. Vitamins 5. Minerals 6. water

Why You Need Food  The amount of energy needed to raise the temperature of one gram of water by one o C = 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 Fats:  Liquid at room temperature  Cooking oils  Saturated 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. Breaks food down into molecules the body can use 2. The molecules get carried throughout the body by the blood 3. 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 Review Questions  Pg. 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 Review Questions  Pg. 529  #’s 1-3  WRITE QUESTIONS AND ANSWERS!