Digestion and Excretion

Transcription

1 Digestion and Excretion Nutrition What do you think? Read the two statements below and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you ve read this lesson, reread the statements and see if you have changed your mind. Before Statement After 1. An activity such as sleeping does not require energy. Key Concepts Why do you eat? Why does your body need each of the six groups of nutrients? Why is eating a balanced diet important?. All fats in food should be avoided. Why do you eat? How do you decide what to eat and when to eat it? You could survive for weeks without food. However, you might feel hungry just a few hours after eating a meal. Hunger is your body s way of telling you that it needs food. Why does your body need food? Food contains energy. Food gives your body the energy and nutrients it needs to survive. Energy Every activity you do, such as riding a bike and even sleeping, uses energy. Your digestive system processes the food you eat. It releases the energy from this processed food. The energy is used for cellular processes and all activities that you do. Measuring Energy The amount of energy in food is measured in Calories. A Calorie (Cal) is the amount of energy it takes to raise the temperature of 1 kg of water by 1 C. How much energy do foods contain? Each food contains a different amount of energy. One grape contains Cal. One slice of cheese pizza might have 0 Cal. All foods give your body energy to use. Identify Main Ideas Fold a sheet of paper into three columns. Label the columns K, W, and L. Write what you already know about nutrition under the K. Write what you want to learn under the W. After you read this lesson, write what you learned about nutrition under the L. 1. Determine Which food would provide your body with more energy a grape or a slice of cheese pizza? Why? Reading Essentials Digestion and Excretion 41

2 Key Concept Check. Explain Why do you eat? 3. Describe What would you include in a lunch that you wanted to be high in protein? Reading Check 4. Identify How does your body obtain amino acids that cannot be made in cells? Your Energy Needs The amount of energy a person needs depends on several factors. Some of those factors are weight, age, activity level, and gender. For example, a person with a mass of 68 kg usually burns more Calories than a person with a mass of 45 kg. Playing soccer requires more energy than playing a video game. How does the food you eat supply you with energy? The energy comes from nutrients. Nutrients Food is made of nutrients. Nutrients are substances that provide energy and materials for cell development, growth, and repair. People need different types and amounts of nutrients. A person s nutrient requirements depend on the person s age, gender, and activity level. Toddlers need more fat in their diets than older children do. Women need more calcium and iron than men do. Older men and women need more calcium than younger adults. Active people need more protein than people who are less active. There are six groups of nutrients. Each group plays a role in maintaining your health. Groups of Nutrients The six groups of nutrients are proteins, carbohydrates, fats, vitamins, minerals, and water. Each nutrient has a different function in the body. To be healthy, you need to eat nutrients from each group every day. Different foods contain different combinations of these nutrients. A healthful diet includes a variety of foods. Proteins Most of the tissues in your body are made of proteins. A protein is a large molecule that is made of amino acids and that contains carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Proteins have many functions. Proteins relay signals between cells and protect against disease. They also provide support to cells and speed up chemical reactions. All of these functions are needed to maintain homeostasis. Homeostasis keeps an organism s internal condition consistent even when there are changes to the organism s environment. Combinations of 0 different amino acids make up the proteins in your body. Your cells can make more than half of these amino acids. The rest of the amino acids must come from the foods that you eat. Some foods that are good sources of protein are red meat, eggs, beans, and peanut butter. 4 Digestion and Excretion Reading Essentials

3 Carbohydrates Pasta, bread, and potatoes all have high levels of carbohydrates (kar boh HI drayts). Carbohydrates are molecules made of carbon, hydrogen, and oxygen atoms and are usually the body s main source of energy. Carbohydrates are usually found in one of three forms starches, sugars, or fibers. All carbohydrates are made of sugar molecules. These molecules are linked together like a chain. It is best to eat foods that have carbohydrates from whole grains. Whole grains are easy to digest. Other foods that are high in carbohydrates include red beans, vegetables, and fruit. Fats You need a certain amount of fat in your diet and on your body to stay healthy. Fats, also called lipids, provide energy and help the body absorb vitamins. They are a major part of cell membranes. Body fat helps to insulate against cold temperatures. Most people get plenty of fat in their diets. Too much fat in your diet can lead to health problems. Only about 5 35 percent of the Calories you consume should be fats. Fats are classified as either saturated or unsaturated. A diet high in saturated fats can increase levels of cholesterol. High levels of cholesterol can increase the risk of heart disease. Most of the fat in your diet should come from unsaturated fats. Foods such as fish, nuts, and liquid vegetable oils are sources of unsaturated fats. Vitamins Vitamins are nutrients that are needed in small amounts for growth, regulating body functions, and preventing some diseases. You can get most of the vitamins that your body needs by eating a well-balanced diet. If you do not get enough of one or more vitamins in your diet, then you might develop symptoms of vitamin deficiency. The symptoms depend on which vitamin you are not getting enough of. The table below lists some of the vitamins people need in their diets. Vitamin Good Sources Health Benefit Vitamin B milk, meats, vegetables helps release energy from nutrients Vitamin C Vitamin A oranges, broccoli, tomatoes carrots, milk, sweet potatoes, broccoli tissue growth and repair enhances night vision, helps maintain skin and bones Reading Check 5. Describe Why do you need a certain amount of fat in your diet? Reading Check 6. Explain Why do you need vitamins in your diet? Visual Check 7. Identify What foods are good sources of vitamin A? Reading Essentials Digestion and Excretion 43

4 Minerals In addition to vitamins, you need other nutrients called minerals. Minerals are inorganic nutrients nutrients that do not contain carbon that help the body regulate many chemical reactions. In a way, minerals are similar to vitamins. If you do not consume enough of certain minerals, you might develop a mineral deficiency. Minerals are essential for maintaining a healthy body. Some of the minerals that you need in your diet are listed in the table below. Visual Check 8. Identify Which mineral does milk contain? Mineral Good Sources Health Benefit Calcium milk, spinach, green beans builds strong bones and teeth Iron meat, eggs, green beans helps carry oxygen throughout the body Zinc meat, fish, wheat/grains aids in the formation of protein Key Concept Check 9. Discuss Why does your body need nutrients? Make a chart to organize information about the major food groups and to list examples of each. Grains Oils Vegetables Milk Fruits Meat and Beans Water You learned that your body is mostly water. Water is necessary for the chemical reactions that occur in your body. Your body takes in water when you eat and drink. However, you lose water when you sweat, urinate, and breathe. To stay healthy, it is important to replace the water that your body loses. Your body loses more water if you live in a warm climate, if you exercise, or if you become sick. When the water that you lose is not replaced, you might become dehydrated. Dehydration can be serious. Symptoms of dehydration include thirst, headache, weakness, dizziness, and little or no urination. Healthful Eating Imagine walking through a grocery store. Each aisle in the store contains hundreds of different foods. Some foods provide more health benefits than others. A large number of choices can make it difficult to choose foods that are part of a healthful diet. To be a healthful eater, you need to be a smart shopper. Smart shoppers make grocery lists before shopping. They buy products that are high in nutrients. Foods that are high in nutrients come from the major food groups. The major food groups include grains, vegetables, fruits, oils, milk products, and meat and beans. 44 Digestion and Excretion Reading Essentials

5 A Balanced Diet A healthful diet includes carbohydrates, proteins, fats, vitamins, minerals, and water. But how do you know how much of each food group you need to eat? The table below lists the daily recommended amounts of each food group for 9- to 13-year-olds. The nutrient-rich foods that you choose might be different from the nutrient-rich foods eaten by people in China, Kenya, or Mexico. People usually eat foods that are grown and produced in their region. Regardless of where you live, eating a balanced diet ensures that your body has the nutrients it needs to function. Food Group Daily Amount, males, 9 13 years old Daily Amount, females, 9 13 years old Examples of Foods Key Concept Check 10. Explain Why is eating a balanced diet important? Grains 6-ounce equivalent 5-ounce equivalent whole-wheat flour, rye bread, brown rice Vegetables 1 cups cups broccoli, spinach, carrots Fruits 1 1 cups 1 1 cups apples, strawberries, oranges Oils 5 teaspoons or less 5 teaspoons or less canola oil, olive oil, avocados Milk 3 cups 3 cups milk, cheese, yogurt Meat and Beans 5 ounces or less 5 ounces or less fish, beans, lean beef, lean chicken Food Labels What foods would you buy to follow the recommended guidelines in the table above? Most grocery stores sell many varieties of bread, milk, meat, and other types of food. How do you know what nutrients these foods contain? You can look at their food labels. Food labels help you determine the amount of protein, carbohydrates, oils, and other substances in food. Be careful when reading a food label. The label lists a food s nutrients per serving, not per container. You should also look at the number of servings per container. The number of servings is also included on the food label. Visual Check 11. Identify How many cups of vegetables should a 9- to 13-year-old female have in her daily diet? (Circle the correct answer.) a. 1 1 b. c Discuss why it is important to read food labels. Reading Essentials Digestion and Excretion 45

6 Mini Glossary Calorie (Cal): the amount of energy it takes to raise the temperature of 1 kg of water by 1 C carbohydrate (kar boh HI drayt): a molecule that is made of carbon, hydrogen, and oxygen atoms and is usually the body s main source of energy fat: also called a lipid, it provides energy and helps the body absorb vitamins mineral: an inorganic nutrient a nutrient that does not contain carbon that helps the body regulate many chemical reactions protein: a large molecule that is made of amino acids and that contains carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur vitamin: a nutrient that is needed in small amounts for growth, regulating body functions, and preventing some diseases 1. Review the terms and their definitions in the Mini Glossary. Write a sentence describing why it is important to include carbohydrates in your diet.. Complete the table below by listing the nutrients that you might get from the breakfast foods. Keep in mind that there might be more than one nutrient in each food. Food scrambled eggs one slice of cheese What do you think Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind? two slices of whole-wheat toast ConnectED small glass of orange juice Nutrients protein vitamins Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson s resources. two slices of bacon 3. Plan a meal that contains a food from each of the six food groups. Write your menu on the lines below. END OF LESSON 46 Digestion and Excretion Reading Essentials