Chapter 15 Food and Digestion Why You Need

Chapter 15: Food and Digestion

Why You Need Food • Food provides your body with materials for growing and gives you energy. • Nutrients- the substances in food that provide the raw materials and energy that the body needs.

6 Groups of Essential Nutrients • Carbohydrates • Vitamins • Fats • Minerals • Proteins • Water

Energy • Calorie- The amount of energy needed to raise the temperature of one gram of water by one degree Celsius. • Used to measure the amount of energy in foods. • You need a certain amount of calories each day, depending on your age and level of physical activity.

Carbohydrates • Made of carbon, hydrogen, and oxygen. • 1 gram of carb. = 4 Calories of energy • Carbs. provide the raw materials to make cell parts. • 45 -60% of your diet should come from carbs.

Simple Carbohydrates • Glucose- a simple carb. that is the main source of fuel for cells. • Most foods do not contain glucose, your body makes it from other types of sugar. • Glucose is the form of sugar that your body can most easily use.

Complex Carbohydrates • Made of many sugar molecules that are linked together. • Starch- a complex carb. found in potatoes, rice, wheat, and corn. • Your body breaks down starch to get energy. • Fiber- complex carb. found in plants. Cannot be broken down into sugar by the body.

- Food and Energy Carbohydrates • In addition to providing energy, carbohydrates provide the raw materials to make cell parts.

Fats • Made of carbon, hydrogen, and oxygen • One gram of fat = 9 Calories of energy • Functions of fats: - Make up cell membrane - Protects internal organs • No more than 30% of daily intake should come from fat.

Types of Fats Saturated Solid at room temp, meat and dairy Unsaturated Liquid at room temp, cooking oils Trans Made by adding Hydrogen to veg. oils, Help foods stay fresh, margarine, chips

- Food and Energy Fats • Many foods contain saturated, unsaturated, and trans fats. Unsaturated fats are considered to be more healthful than saturated fats and trans fats.

Proteins • Made of carbon, hydrogen, and oxygen, and nitrogen • Needed for tissue growth/repair and chemical reactions. • 10 -35% of your daily diet should come from proteins.

• Amino Acids- link together to make proteins. - There are 20 amino acids. - Your body can make some amino acids. -Essential amino acids- must come from foods you eat.

• Complete proteins- contain all of the 20 amino acids, come from animals - Ex: meat and eggs • Incomplete proteins- only have some amino acids, come from plants -Ex: beans, grains, nuts • To get all of the essential amino acids, you must have a varied diet.

Vitamins and Minerals • Your body only needs very small amounts. • Do not provide energy. • Help body carry out processes. • Vitamins- helper molecules for chemical reactions. - Ex: Vitamin K helps blood clot

• Fat-soluble vitamins- stored in fatty tissues in the body. • Water-soluble vitamins- dissolve in water, not stored in the body. • Scurvy- disease caused by lack of vitamin C. Causes bleeding gums, stiff joints, and wounds that won’t heal.

- Food and Energy Vitamins and Minerals • Vitamins act as helper molecules in a variety of chemical reactions in the body.

• Minerals- nutrients that are not made by living things. • Present in soil, absorbed through plant roots. • Calcium- needed for strong bones. • Iron- needed for red blood cell function. • Both vitamins and minerals are needed in small amounts to help chemical reactions occur.

- Food and Energy Vitamins and Minerals • Nutrients that are not made by living things are called minerals.

Water • Makes up about 65% of your weight. • The most important essential nutrient because all of the body’s processes take place in water. • Normal recommended daily amount of water = 2 liters/day

Guidelines for a Healthy Diet • United States Department of Agriculture (USDA)- provides personalized guidelines to stay healthy • 13 -year-old girl needs 1600 -2200 Calories/day. • 13 -year-old boy needs 1800 -2400 Calories/day

Food Labels • Allow you to evaluate a single food or compare two different foods. • Serving Size- the size of a single serving and how many are in the container. • Calories- how much energy you get from one serving. • Percent Daily Value- how the nutritional content of one serving fits into the diet. Based on a 2, 000 Cal/day diet.

• Ingredientslisted in order by weight, starting with the main ingredient. • Dietary Reference Intakes (DRIs)amount of nutrients needed every day.

Food Labels - Healthy Eating • Food labels allow you to evaluate a single food as well as to compare the nutritional value of two different foods. 1. Serving Size: This information tells you the size of a single serving and the number of servings in the container. 2. Calories: This information tells you how much energy you get from one serving of this food, including how many calories come from fat. 3. Percent Daily Value: The Percent Daily Value shows you how the nutritional content of one serving fits into the recommended diet for a person who consumes 2, 000 calories a day. 4. Ingredients: The ingredients are listed in order by weight, starting with the main ingredient.

- Food and Energy Percentages • A percentage (%) is a ratio that compares a number to 100. For example, 30% means 30 out of 100. • Suppose that a person eats a total of 2, 000 calories in one day. Of those calories, 300 come from protein. Follow these steps to calculate the percentage of calories that come from protein. • 1. Write the comparison as a fraction: • 2. Multiply the fraction by 100% to express it as a percentage:

- Food and Energy Percentages • Practice Problem • Suppose that 540 calories of the person’s 2, 000 calorie total come from fats. What percentage of the calories come from fats? • 27%

Digestion • 3 functions of the digestive system: - Breaks down food into molecules - Absorbs molecules into the blood - Eliminates wastes from the body • Digestion- the process by which the body breaks down food. - Mechanical- food is physically broken down. Ex: Chewing food - Chemical- chemicals break foods down. Ex: Amylase breaking down starch.

• Absorption- the process by which nutrients pass through the wall of your digestive system into your blood. • Materials that are not absorbed are eliminated.

- The Digestive Process Begins The Mouth • Both mechanical and chemical digestion begin in the mouth.

The Mouth - The Digestive Process Begins • The shape of an enzyme molecule is specific to the shape of the food molecule it breaks down. Here an enzyme breaks down a starch into sugars.

The Esophagus • Esophagus- muscular tube that connects the mouth to the stomach. • Epiglottis- flap of tissue that seals off the wind-pipe when you swallow. Makes food go down the esophagus instead of the wind-pipe. • Mucus- thick, slippery substance produced by the body. Lines the esophagus. • Peristalsis- wave-like motion caused by contractions of smooth muscles in the esophagus.

The Stomach • Stomach- J-shaped muscular pouch located in the abdomen. • Mechanical and chemical digestion happen in the stomach. - Mechanical digestion- churning - Chemical digestion- digestive juice *Pepsin- enzyme in digestive juice * Hydrochloric Acid- strong acid in digestive juice • Stomach is lined with mucus, prevents stomach acid from burning the stomach cells.

- The Digestive Process Begins The Stomach • Most mechanical digestion and some chemical digestion occur in the stomach.

Final Digestion and Absorption • Small Intestine- part of digestive system where most chemical digestion takes place. In line after stomach. • About 6 meters long. • Named for its small diameter- 2 to 3 cm wide. • Almost all chemical digestion and absorption takes place in the small intestine.

The Small Intestine - Final Digestion and Absorption • The small intestine is the part of the digestive system where most chemical digestion takes place.

The Small Intestine - Final Digestion and Absorption • Tiny finger-shaped projections called villi line the inside of the small intestine. Villi absorb nutrient molecules. The molecules pass from the villi into blood vessels. Villi increase surface area.

The Liver • Liver- located in the upper right portion of the abdomen. • Largest organ inside the body. • Role of the liver in the digestive system is to produce bile. • Bile- molecule that breaks up fat particles. • Gallbladder- bile comes here from the liver, bile is stored here. • Bile physically breaks up food.

The Pancreas • Pancreas- triangular shaped organ between the stomach and small intestine. • In the digestive system, produces enzymes that flow into the small intestine and help break up starches, proteins, and fats.

The Large Intestine • Large Intestine- last section of the digestive system. • About 1. 5 meters long • Named for its wide diameter (about 6 cm). • Contains helpful bacteria that aid in digestion and produce vitamins (Vitamin K). • Absorbs water into the bloodstream.

The End • After undigested food passes through the large intestine, it is eliminated from the body. • Rectum- short tube at the end of the digestive tract where waste material is converted into a solid. • Anus- muscular opening at the end of the rectum where waste material is eliminated from the body.