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Section 1 Section 1 Focus Your Body’s Need for Food Overview Before beginning this section review with your students the objectives listed in the Student Edition. This section introduces students to the role each nutrient plays in maintaining a healthy body. Students will also learn about health disorders related to malnutrition. Bellringer Have students list the nutrients they think they get from eating a small bag of chips and a bottle of soda pop. Then have them estimate the number of calories this “snack” provides. If possible, bring in samples of each—empty bags and bottles are okay. Students may be amazed at how many servings are in even these “individual sizes” of food and drink and how that multiplies the calories—and the relatively poor nutrition. LS Logical Bio 11C Objectives Food Your body uses energy to move, to grow, and even to lie still and sleep. The amount of energy you need depends on many factors, including your age, your sex, your rate of growth, and your level of ● Relate the role of physical activity. Different activities use different amounts of carbohydrates, proteins, energy, as shown in Figure 1. lipids, vitamins, minerals, You obtain energy from the nutrients in the foods and beverages and water in maintaining a healthy body. 4B 11C TAKS 2 you consume. A nutrient is a substance required by the body for energy, growth, repair, and maintenance. Nutrients in food and ● Describe each of the parts beverages include carbohydrates, lipids, proteins, vitamins, and of the USDA food guide minerals. Each nutrient plays a different role in keeping your body pyramid. 11C healthy. Water is essential for life and for maintaining health. ● Name one health disorder The large molecules in food must be broken down in order to be associated with high levels absorbed into the blood and carried to cells throughout the body. of saturated fats in The process of breaking down food into molecules the body can use 10A 11C TAKS 2 the diet. is called digestion . Your cells then break the chemical bonds of the Key Terms digested food molecules and use the energy that is released to make ATP during the process of cellular respiration. nutrient The energy available in food is measured by using a unit called a digestion calorie. A calorie is the amount of heat energy required to raise the calorie temperature of 1 g of water 1°C (1.8°F). The greater the number of vitamin mineral calories in a quantity of food, the more energy the food contains. Because a calorie represents a very small amount of energy, nutritionists use a unit called the Calorie (with a capital C), which is equal to 1,000 calories. On food labels and throughout this book, the word calories represents Calories (1,000 calories). ● Identify five nutrients found in foods. 9A Motivate Identifying Preconceptions GENERAL Have students list the nutrients necessary for proper body functioning and food sources where each nutrient can be found. (For example: Calcium is necessary for healthy teeth and bones; calcium can be found in milk.) Have students revisit the list after reading Section 1. LS Verbal Bio 11C Figure 1 Energy required for common activities. Quiet activities require just a little more energy than what it takes to keep you alive. Strenuous activities require more energy. 900 Chapter Resource File pp. 900–901 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 9D TEKS Bio 4B, 9A, 9D, 10A, 11C Teacher Edition TAKS Obj 4 IPC 8A TEKS Bio 3F, 9A, 11C TEKS IPC 8A 900 • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL Chapter 39 • Digestive and Excretory Systems Transparencies TT Bellringer TT Nutrients in Food Energy and Building Materials Each nutrient plays a different role in maintaining a healthy body. Carbohydrates, proteins, and lipids are involved in providing both energy and building materials to the cells. Organizing Information Make a table to organize information about food nutrients and water. Across the top, write the headings Carbohydrates, Proteins, Lipids, Vitamins, Minerals, and Water. Along the left side, write Functions, Food sources, and Additional comments. Add information to the table as you read Section 1. Carbohydrates Carbohydrates that exist as single sugar molecules are called monosaccharides or simple carbohydrates. Carbohydrates made of two or many sugar molecules linked together by chemical bonds are called complex carbohydrates. Complex carbohydrates must be digested (broken down) into simple sugars before cells can use their energy. Many foods contain carbohydrates, as shown in Figure 2. Glucose, fructose, and other simple sugars are found in fruits, honey, and onions. Glucose, a simple sugar, is used by cells for energy, and it can be directly absorbed into your bloodstream. Table sugar contains sucrose, two simple sugars linked together. Starches are long chains of sugars found in cereal grains and in vegetables such as potatoes, beans, and corn. Cellulose is a major component of plant cell walls and is found in all foods that come from plants. Cellulose, which is a major part of fiber, does not provide energy because we do not have the enzymes to digest it. However, cellulose aids in human digestion by stimulating the walls of the digestive tract to secrete mucus, which helps pass food through the digestive tract. If excess carbohydrates are consumed, they are stored as the carbohydrate glycogen in the liver and in some muscle tissue. Glycogen can later be broken back down into glucose when the body needs energy. The remainder of the excess glucose is converted to fat and stored in fatty tissue. SKILL BUILDER Interactive Reading Assign Chapter 39 of the Holt Biology Guided Audio CD Program to help students achieve greater success in reading the chapter. English Language Learners LS Auditory GENERAL Have students study Figure 2. Ask students why it is important for weight-conscious people to get a balance of nutrients from carbohydrate- and protein-rich foods while limiting fat intake. (Carbohydrates take less time to digest, providing quick energy and satisfying hunger quickly. Proteins take longer to digest providing energy and satisfying hunger over a longer period of time. Both release only 4 Calories per gram. Although fats provide energy and satisfy hunger over a longer period of time than carbohydrates or proteins do, they contain more than twice the number of Calories per gram.) Tell students that insufficient protein in the diet can cause a person to eat more because hunger and energy requirements are not met for as long as they need to be. However, as Figure 2 shows, proteins contain hidden fats and should be consumed in lesser quantities than carbohydrates. LS Visual Bio 11C Although most foods contain a mix of nutrients, some foods are richer than others in a specific nutrient. Carbohydrate-rich foods Protein-rich foods Fat-rich foods (Carbohydrates contain 4 calories per gram.) Breads, pasta, grains, cereals, potatoes, fruits (Proteins contain 4 calories per gram.) Fish, eggs, poultry, beef pork, nuts, legumes, milk, cheese, tofu (Fats contain 9 calories per gram.) Milk, cheese, meats, butter, olives, avocados, fried foods, oils, chips 901 Have students identify some of the various chemical bonds that are broken in the mouth, stomach, and small intestine by digestive enzymes. For example, the mouth’s saliva contains amylase which breaks the chemical bonds of long starch molecules, while pepsin, which is added in the stomach, begins the chemical breakdown of protein molecules. TAKS 4 IPC 8A READING Using the Figure Figure 2 Nutrients in food IPC Benchmark Fact Teach HISTORY CONNECTION ATP is the energy currency of all living cells. Fritz Lipmann isolated ATP from muscle tissue in 1929. In research he began in 1941, he discovered that ATP and similar compounds shuttle energy around the cell, once the energy is captured from carbohydrates, fats, and proteins during cellular respiration. In 1953 Lipmann shared the Nobel Prize in physiology or medicine for his discoveries. Planner CD-ROM • Reading Organizers • Reading Strategies • Problem Solving Using Food Labels to Calculate Percentage of Nutrients and Calories GENERAL Bio 3F, 9A Chapter 39 • Digestive and Excretory Systems 901 Proteins Teach, continued continued Teaching Tip GENERAL The digestive products of proteins—amino acids—are normally used by the body for making other protein molecules, such as enzymes and antibodies. When more protein is eaten than is needed by the cells, the amino acids are used for energy or converted to fat. The body requires 20 different amino acids to function. A child’s or teen’s body can make 10 of the amino acids from other amino acids. The other 10, called essential amino acids, must be obtained directly from food. Most animal products, such as eggs, milk, fish, poultry, and beef, contain all of the essential amino acids. No single plant food contains all of the essential amino acids. But eating certain combinations of two or more plant products can supply all the essential amino acids. Adults must get eight essential amino acids from food. The guidelines for healthy eating are summarized in the USDA (U.S. Department of Agriculture) food guide pyramid, as shown in Figure 3. The pyramid lists the daily number of servings needed from each food group to obtain a variety of nutrients in your diet. www.scilinks.org Topic: Foods Grown in Texas Keyword: HXX4007 Analyzing Vegetarian Diets Have students make a list of protein food sources and note whether the food contains all of the essential amino acids or only some of them. Then discuss the different types of vegetarian diets such as those that omit only red meat, omit all meat but fish, omit all meat but include animal products such as milk and eggs, and omit all animal products. Have students create a meal for each of these diet types and decide how it is difficult to obtain a nutritionally complete meal for each diet. LS Logical Bio 11C Lipids Lipids, organic compounds that are insoluble in water, are used to make steroid hormones and cell membranes and to store energy. Fats are lipids that store energy in plants and animals. Fats are Figure 3 The USDA food guide pyramid SKILL BUILDER Interpreting Visuals Have students look at Figure 3 and Figure 4. Ask students to write a brief essay explaining how the percentage of calories from each dietary nutrient in Figure 4 relates to the number of servings of each food group in Figure 3. (Carbohydrates are mainly found in the lower tiers of the pyramid, which corresponds to the high percentage of calories from carbohydrates. Proteins are mainly in the second level and lipids are in the first and second levels of the pyramid, which corresponds to lower percentages. The percentage of calories from proteins may seem small compared to the percentage from fats since their number of recommended servings are similar, but fats carry twice the calories that proteins do.) LS Verbal TAKS 1 Bio/IPC 2C; Bio 3E Food groups at the bottom of the pyramid should be eaten in greater amounts than those at the top. Fats, oils, and sweets (Use sparingly.) Milk, yogurt, cheese (2–3 servings a day) Vegetables (3–5 servings a day) Fruits (2–4 servings a day) Grains (6–11 servings a day) Serving Sizes Milk, yogurt, cheese • 1 cup of milk • 1 cup of yogurt • 1.5 oz of cheese • 2 oz of processed cheese Meat, beans, eggs, nuts • 1 egg • 2 tbsp of peanut butter • 2–3 oz of meat, chicken, or fish 1 cup of cooked beans •— 2 Vegetables • —12 cup of vegetables • —34 cup of vegetable juice • 1 cup of raw, leafy vegetables Fruits • 1 apple, banana, or orange • —12 cup of fruit • —34 cup of fruit juice Grains • 1 slice of bread 1 cup of rice or •— 2 pasta 1 cup of hot cereal •— 2 • 1 oz cold cereal • 1 tortilla 902 Transparencies TT The USDA Food Guide Pyramid pp. 902–903 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10B TEKS Bio 4B, 10B Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 2 Bio 10A TEKS Bio 3E, 10A, 11A, 11C TEKS Bio/IPC 2C, 2D 902 Meat, beans, eggs, nuts (2–3 servings a day) Chapter 39 • Digestive and Excretory Systems Trends in Nutrition Food Guides Around the World Countries around the world use different graphics to illustrate their dietary guidelines. Canada uses a four-banded rainbow, with each color representing one of its food groups and the width of each band representing the amount recommended. Israel uses a chalice with water at the top, largest section and grains at the wide base of the chalice. The Philippines uses a sixpointed star. The United Kingdom, Germany, and Norway use a wheel or dinner plate divided into sections that represent the food groups. The size of each section indicates its relative importance to the total diet. Bio 3E stored around organs and act as padding and insulation. Fats also act as solvents for fat-soluble vitamins. Although lipids are essential nutrients, too much fat in the diet is known to harm several body systems. For example, a diet high in saturated fats is linked to high blood-cholesterol levels, which in turn may be connected to cardiovascular diseases. It is recommended that no more than 30 percent of your day’s calories come from fats and that most of these fats be unsaturated. Examples of foods containing fats are shown in Figure 2. Complex carbohydrates (48%) Protein (12%) Unsaturated fats (20%) Simple carbohydrates (10%) Balancing Nutrients and Energy Demonstration Regardless of their source, the excess calories you eat will be stored as either glycogen or body fat, and you will gain weight. If you use more calories than you take in, additional energy will be obtained from your body’s energy stores, and you will lose weight. Your diet and overall activity level determine in part whether you store excess calories as glycogen or as fat. Figure 4 summarizes what percentage of the day’s total calories should come from each nutrient. Obesity is described as being more than 20 percent heavier than your ideal body weight. Obesity significantly increases an individual’s risk of diabetes, heart disease, osteoarthritis, and many other disorders. Regular physical activity is important in maintaining energy balance. Saturated fats (10%) Figure 4 A balanced meal. The percentages of the day’s total calories that should come from each nutrient are shown. At least half of your day’s calories should come from foods high in complex carbohydrates. Bring some French fries and a plain baked potato to class, or show students a picture of these foods. Have students examine the baked potato and the French fries carefully, and ask them to brainstorm differences between the two foods with regard to cooking, taste, and nutritional value. (Unlike the baked potato, French fries are peeled, sliced, fried in oil or fat, and salted.) Ask students how the body is affected by a diet high in oils, fats, and salt. (Oils and fats increase caloric intake. Saturated fats may increase cholesterol levels. A diet high in salt can cause fluid to be retained in the body. Over a long period of time, high salt intake can contribute to hypertension.) LS Visual TAKS 1 Bio/IPC 2D; Bio 11C Obesity and Health TAKS 2 Obesity and Health TAKS 2 Bio 10A; Bio 11A, 11C T he National Center for Health Statistics reported that by the year 2000, 31 percent of adults in the United States were obese. Medically, obesity is defined as having a body mass index (BMI) of 30 or higher. To calculate your BMI, first multiply your weight in pounds by 703, and then divide by your height in inches squared. BMI weight in pounds 703 (height in inches) 2 For example, someone who is 6'0" (72 inches) tall and who weighs 189 pounds has a body mass index of (189 703) (72 72) 25.6. Unfortunately, being obese often has a serious consequence— diabetes. Late-onset diabetes affected 14 million Americans in 2000, and 80 percent of those so affected were obese. Like the rate of obesity, the rate of late-onset diabetes is soaring, up 40 percent in the last 10 years. Late-onset diabetes is a disorder in which the hormone insulin is unable to induce the body’s cells to take up glucose from the blood. Glucose-starved tissues consume their own protein, and waste away. Diabetes is the leading cause of kidney failure, blindness, and amputation in adults. What is the link between obesity and late-onset diabetes? Researchers have recently found that fat cells produce a hormone called resistin that prompts cells to resist insulin. Mice given resistin by researchers lose much of the ability to respond to insulin and fail to take up blood sugar. Drugs that inhibit resistin restore insulin’s effectiveness. Researchers hypothesize that resistin blocks the same glucosetransporting molecules in the plasma membrane that insulin activates. 903 Cultural Awareness Mediterranean Diets and Heart Disease The French, Greeks, and other southern Europeans suffer from less heart disease than either their northern European neighbors or Americans. The Mediterranean diet is thought to play a role. The Mediterranean diet is rich in canola oil, fish, fruits, cereals, and beans. Even when researchers account for age, sex, alcohol intake, and lifestyle differences, eating a Mediterranean diet appears to reduce the probability of heart problems. MISCONCEPTION ALERT Athletes, Proteins, and Carbohydrates A common misconception is that athletes need to eat more protein to improve their athletic performance and maintain greater muscle mass. Actually, a diet rich in complex carbohydrates is much more effective in sustaining intense muscle activity than a diet high in protein. Bio 11C Teacher’s Notes Be sensitive to those students in your class that may be overweight. The Centers for Disease Control and Prevention publishes the Morbidity and Mortality Weekly Report. If possible, bring some of these to class. Have students conduct research about these topics and present their research in oral reports and/or fact sheets. Discussion Ask students: Is a person who is 5’8” and 180 pounds obese? (No, the person’s BMI is 27.4.) What hormone does not work appropriately in diabetes? (insulin) What hormone causes cells not to respond to insulin? (resistin) What type of cell produces resistin? (fat cells) How does that fact link obesity with diabetes? (Obese people have more fat cells, which produce more resistin, which causes more insulin to be blocked, which can lead to diabetes.) Chapter 39 • Digestive and Excretory Systems 903 Vitamins, Minerals, and Water Vitamins, minerals, and water are required in our diets. They do not provide energy, but they contribute to many different functions, including regulating the reactions that release energy. Teach, continued continued Activity Analyzing Diet Have students list the kinds and amounts of each food they eat in a day. The next day, have students compare their number of servings for each food group to the recommended amounts given in the food pyramid shown in Figure 3, as well as the amount of vitamins and minerals they are receiving. Ask students to plan how they can reasonably change their diet to make it more balanced. LS Intrapersonal Bio 9A, 11C Using the Figure Diagnosing Deficiencies Tell students to imagine that they are physicians. Ask them to use information in Table 1 to answer the following questions: If a child suffers from frequent internal infections and has difficulty seeing in dim light, what problem would you suspect? (The child likely is suffering from a vitamin A deficiency.) What foods would you prescribe to someone who has sore gums and tends to bruise easily? (fruit, especially citrus fruits) LS Interpersonal TAKS 1 Bio/IPC 2C; Bio 11C Group Activity Vitamin Nutrition Organize students into groups. Give each group a few boxes of cereal. Ask the groups to identify the vitamins that are listed on the cereal labels. Have students use Table 1 to list the role of each vitamin and the effects of a deficiency in that vitamin. LS Visual Co-op Learning pp. 904–905 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TEKS Bio 4B, 9A, 10A, 11A, 11C Teacher Edition TAKS Obj 1 Bio/IPC 2C, 3B, 3C TAKS Obj 2 Bio 10A TEKS Bio 9A, 10A, 11A, 11C, TEKS Bio/IPC 2C, 3B, 3C 904 Vitamins Many different vitamins , organic substances that occur in many foods in small amounts, are necessary in trace amounts for the normal metabolic functioning of the body. Vitamins dissolve in either water or fat, as summarized in Table 1. Fat-soluble vitamins—vitamins A, D, E, and K—can be stored in body fat. Excessive amounts of vitamins A and D can be toxic. Excess water-soluble vitamins—vitamin C and the B vitamins—are excreted in urine and must be replenished by the diet. GENERAL Table 1 Vitamins Vitamin Food sources Role Effects of deficiency Most vegetables, nuts, whole grains, organ meats Assists in carbohydrate metabolism, helps nerves and heart to function properly Digestive disturbances, impaired senses Vitamin B2 (riboflavin) Fish, poultry, cheese, yeast, green vegetables Needed for healthy skin and tissue repair, assists in carbohydrate metabolism Blurred vision, cataracts, cracking of skin, lesions of intestinal lining Vitamin B3 (niacin) Whole grains, fish, poultry, tomatoes, legumes, potatoes Keeps skin healthy, assists in carbohydrate metabolism Mental disorders, diarrhea, inflamed skin Vitamin B12 (cobalamin) Meat, poultry, green vegetables, milk, dairy products Needed for formation of red blood cells Reduced number of red blood cells Citrus fruits, strawberries, potatoes Needed for wound healing, healthy gums and teeth Swollen and bleeding gums, loose teeth, slow-healing wounds Vitamin A (retinol) Butter, eggs, liver, carrots, green leafy vegetables, sweet potatoes Keeps eyes and skin healthy, needed for strong bones and teeth Infections of urinary and digestive systems, night blindness Vitamin D (cholecalciferol) Salmon, tuna, fish liver oils, fortified milk, cheese Assists in calcium uptake by the gut, needed for strong bones and teeth Bone deformities in children, loss of muscle tone Vitamin E (tocopherol) Many foods, especially wheat and other vegetable oils, olives, whole grains Protects cell membranes from damage by reactive oxygen compounds (free radicals) Reduced number of red blood cells, nerve tissue damage in infants Vitamin K (menadione) Leafy green vegetables, liver, cauliflower Needed for normal blood clotting Bleeding caused by prolonged clotting time Water-soluble Vitamin B1 (thiamin) Vitamin C (ascorbic acid) Fat-soluble 904 Vitamin Overdoses Some people have the idea that if a little is good, then a lot must be better. Unfortunately, this is not the case with certain vitamins. For example, overdoses of vitamin A can cause enlargement of the liver and spleen. Overdoses of vitamin D can cause kidney damage and calcification of soft tissues. Although vitamins A and D are both Chapter 39 • Digestive and Excretory Systems fat-soluble, making them more difficult for the body to eliminate, even the water-soluble vitamins have some negative effects if overused. Massive doses of vitamin C can cause kidney stones and enhance blood coagulation. Megadoses of niacin, one of the B vitamins, can cause liver damage and gout. Bio 11C Minerals Different minerals are required to maintain a healthy body. Minerals are naturally occurring inorganic substances that are used to make certain body structures and substances, for normal nerve and muscle function, and to maintain osmotic balance. Some minerals are essential for enzyme function. Minerals are not produced by living organisms. Minerals must be replaced on a daily basis because they are soluble in water. Teeth and bones require the minerals calcium and phosphorus. Iron is required for transporting oxygen. Magnesium, calcium, sodium, potassium, and zinc help regulate function of the nerves and muscles. Trace elements, such as those listed in Table 2, are minerals present in the body in small amounts. Humans usually obtain adequate amounts of the required trace elements directly from the plants they eat or indirectly from animals that have eaten plants. Teaching Tip Calcium and Vitamin D Ask students to identify the predominant mineral in milk. (calcium) Ask students to identify what nutrient is added to milk, (vitamin D) and then ask students why. (Accept any answers that tie vitamin D and calcium together.) Tell students that vitamin D is needed for the absorption of calcium from the intestines. Explain that rickets, a disease that affects growing bones and is caused by a vitamin D deficiency, used to be common in the United States. In the 1930s the federal government mandated the enrichment of milk with vitamin D. Today rickets is virtually unknown in the United States. LS Verbal Water You can survive only a few days without water, though you can live several weeks without food. Water is used by the body as a medium to transport gases, nutrients, and waste products. Water also plays a role in regulating body temperature. Two-thirds of the body’s weight is water. Table 2 Trace Elements Trace element Food sources Role Bio/IPC 3C; Bio 11C Iodine Seafood, plants grown in iodine-rich soil, iodized table salt Synthesis of thyroid hormones Cobalt Leafy vegetables, liver, kidney Synthesis of vitamin B12 Zinc Meat, shellfish, dairy products Synthesis of digestive enzymes, proper immune function Molybdenum Legumes, cereals, milk Protein synthesis Manganese Whole grains, nuts, legumes Hemoglobin synthesis, urea formation Selenium Meat, seafood, cereal grains Preventing chromosome breakage Close Reteaching Bring in a label from a cereal box. List the nutrients in a table on the board or overhead. Have students write the function of each nutrient. Also, students can review their lists of nutrients and sources from the Motivate: Identifying Preconceptions activity at the start of this section. Bio 11C Section 1 Review Predict four nutrients that would be found in a 9A 11C serving of green beans. Compare the functions of carbohydrates and pro- teins in maintaining a healthy body. guide pyramid provides. 11C Evaluate the roles vitamins, minerals, and water play in maintaining a healthy body. Critical Thinking Applying Information Your friend wants to feed her elderly grandmother more food in order to keep her healthy. Is this a good idea? Explain. 10A 11C 11A 11C Describe the type of information the USDA food 4B 10A 11C TAKS Test Prep One of the functions of lipids in the body is to 9A A enhance enzyme C make steroid activity. hormones. B make glycogen. D make proteins. 905 Answers to Section Review 1. carbohydrates, vitamins, minerals, protein Bio 9A, 11C 2. Both can be used as a source of energy, but the body usually uses amino acids from proteins as building blocks for other proteins. Bio 11A, 11C 3. The food guide recommends the number of servings of each different type of food group a person should eat daily to obtain a variety of nutrients in the diet. Bio 11C 4. Vitamins enhance enzyme activity. Minerals are necessary for making certain body structures and substances, for normal nerve and muscle functions, for maintaining osmotic balance, and for enzyme function. Water transports GENERAL gases, nutrients, and waste and regulates body temperature. TAKS 2 Bio 4B, 10A; Bio 11C 5. Answers will vary. Students who disagree might argue that elderly people have a lower metabolic rate, and thus need fewer calories. Students who agree might point out that elderly people tend to eat less and may get sick if they become malnourished. TAKS 2 Bio 10A; Bio 11C 6. A. Incorrect. Enzyme activity is enhanced by vitamins and minerals. B. Incorrect. Glycogen is made of carbohydrates. C. Correct. Lipids make steroid hormones. D. Incorrect. Proteins are made of amino acids. Bio 9A Quiz GENERAL 1. Which nutrient type should make up a majority of your diet? (carbohydrates) 2. Name two nutrients that do not provide energy but are needed to proper enzyme function. (vitamins and minerals) 3. What nutrient could you live only a few days without? (water) Alternative Assessment GENERAL Have students describe any fad diets they may have read about or tried. Have them analyze these diets in terms of how they may fail to provide certain nutrients. TAKS 1 IPC 3B Transparencies TT Trace Elements Chapter 39 • Digestive and Excretory Systems 905 Section 2 Section 2 Digestion Focus Breaking Down Food Objectives Overview Before beginning this section review with your students the objectives listed in the Student Edition. This section introduces students to the functions of the digestive organs and how food is broken down and absorbed. Bellringer Tell students to write down in correct sequence all the organs (at least 5) through which their food passes as it travels along the digestive tract. Then have them try to list any glands or organs (3) that are found along the digestive tract that help digestion but through which food does not pass. TAKS 2 Bio 10A Motivate Imagine you just ate your favorite meal. What happens to that ● Relate the four major funcfood? Before your body can use the nutrients in the food you eat, tions of the digestive system to the processing of food. 10A the large food molecules must be broken down physically and ● Summarize the path of TAKS 2 chemically. The process of breaking down food into molecules the body can use is called digestion. The digestive system is the body food through the digestive system that is involved in the taking in and processing of food for system and the major digestive processes that use by your body cells. The digestive system takes in food, breaks it occur in the mouth, stomdown into molecules small enough for the body to absorb, and gets ach, small intestine, and rid of undigested molecules and waste. large intestine. 10A TAKS 2 As shown in Figure 5, the digestive system is made up of a long, ● Describe how nutrients are winding tube, the digestive tract, that begins at the mouth and absorbed from the digestive winds through the body to the anus. Food travels more than 8 m system into the bloodstream (26 ft) through your digestive tract. The digestive tract includes the or lymphatic system. 10A TAKS 2 mouth, pharynx, esophagus, stomach, small intestine, large intes- ● Identify the role of the pancreas and liver in digestion. 10A TAKS 2 tine, and rectum. Although the liver and pancreas (PAN kree uhs) are not part of the digestive tract, they deliver secretions into the digestive tract through ducts (tubes). Key Terms amylase esophagus pepsin lipase villus colon Digestive System Demonstration Esophagus Salivary glands Hang an 8 m (26 ft) piece of clothesline or rope at the front of the room. Explain to students that it represents the approximate length of the digestive system. Use clothespins and markers to label the clothesline as follows: PART LENGTH AVERAGE TIME FOOD SPENDS HERE Mouth 8 cm (3 in.) 5–30 s Pharynx/ 25 cm (10 in.) 5–10 s esophagus Stomach Small intestine 15 cm (6 in.) 4–6 m (13–20 ft) 2–6 h 3–6 h Large intestine 1.2 m (4 ft) up to 2 d Pharynx Mouth Liver Stomach Duodenum Gallbladder Pancreas Small intestine Large intestine Rectum Figure 5 Processing food. The digestive system breaks down food into individual nutrient molecules that can be absorbed into the bloodstream. Anus 906 LS Visual TAKS 1 Bio/IPC 2C Chapter Resource File pp. 906–907 Student Edition TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 10A,10B Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A TEKS Bio 9C, 10A, 11D TEKS Bio/IPC 2C 906 • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL • Data Sheet for Quick Lab Chapter 39 • Digestive and Excretory Systems Transparencies TT Bellringer TT Digestive System GENERAL Planner CD-ROM • Reading Organizers • Reading Strategies Starting Digestion The digestion of food begins as soon as the food is ingested. The teeth rip and chew food into shreds, and the tongue mixes the pieces with a watery solution called saliva. Taste buds on the tongue are sensitive to certain chemicals in the food. Saliva is secreted into the mouth by three pairs of salivary glands, shown in Figure 5. Saliva moistens and lubricates the food so that it can be swallowed more easily. Saliva also contains amylases (AM uh lay sehs), enzymes that begin the breakdown of carbohydrates such as starch, into monosaccharides (single sugars). The mechanical action of chewing and the chemical action of amylase are both part of the digestion of carbohydrates in the mouth. Notice in Figure 6 that the structure of our teeth helps in the breakdown of food. The two front teeth, the incisors, cut food. The cuspids, or canines, shred food. The back teeth, the molars, crush and grind food. After passing through the region in the back of the throat called the pharynx (FAIR ihnks), the food triggers a swallowing response. The action of swallowing moves the epiglottis (a flap of cartilage) over the opening of the trachea—the tube that leads to the lungs. This action prevents food from entering the trachea and eventually the lungs. Instead, food enters the esophagus (ih SAHF uh guhs). Incisors Cuspid (canine) Bicuspids (premolars) Molars SKILL Uvula Opening of duct of salivary gland Figure 6 Teeth and digestion. Canine and incisor teeth are used for cutting and tearing food. The molars are used to grind food. The esophagus is a long tube that connects the mouth to the stomach. No digestion takes place in the esophagus. Its role is to act as a kind of descending elevator, moving food down to the stomach. The esophagus is about 25 cm (10 in.) long. The lower two-thirds of the esophagus is wrapped in sheets of smooth muscle. Food does not simply fall into the stomach; it is pushed down, as shown in Figure 7. Successive rhythmic waves of smooth muscle contraction in the esophagus, called peristaltic (pehr uh STAHL tihk) contractions, or peristalsis, move the food toward the stomach. Peristalsis can be thought of as waves moving through the muscle with the area where the wave is passing causing the muscle to narrow. It takes about 5 to 10 seconds for food to pass down the esophagus and into the stomach. Esophagus Wave of contraction Food Stomach Figure 7 Peristalsis moves food. Food is pushed down the esophagus and toward the stomach by waves of smooth muscle contractions in the wall of the esophagus. 907 INCLUSION • Learning Disability • Attention Deficit Disorder Using Figure 5, have students write each body part responsible for digestion on a note card. Students will then write the function of each body part in the digestive process. The cards should be numbered on the back to indicate the order the food is processed through the body. The students may study the digestive process by attempting to order the note cards by body part and function. Students may also use the note cards to present the digestive process to the class, small groups, or pairs. REAL WORLD CONNECTION Halitosis (bad breath) results when decomposing food particles accumulate in the mouth, allowing bacteria to flourish. Saliva aids in washing away the food particles. Therefore, people who suffer from any disease that inhibits saliva secretion usually have problems with dental caries and bad breath, as well as difficulty talking, swallowing, and eating. Bio 11D BUILDER Reading Organizer Have students create a reading organizer that lists the organs of the digestive system, their functions, and associated enzymes. If students are confused about any of these, encourage them to use outside sources of information such as an encyclopedia. LS Verbal TAKS 2 Bio 10A Activity GENERAL Salivation Organize the class into groups. Give each group two test tubes with stoppers, four saltine crackers, water, a straw or stirring rod, and an iodine solution. In one test tube stir two crushed crackers with water, then add a few drops of iodine and invert to mix. The solution in the test tube will turn blue-black, indicating the presence of starch. Have a volunteer chew up the other two crackers without swallowing, and spit them into the second test tube. Add some water, stir, and then add a few drops of iodine, and invert to mix. The solution starts out blueblack, but as salivary amylase enzymes start to break the starch down into sugars, the color will fade to purple and eventually disappear. LS Kinesthetic Co-op Learning The Stomach Strategies READING Tonsil The Esophagus Food exits the esophagus and enters the stomach through a muscular valve called a sphincter (SFIHNGK tuhr). The sphincter prevents acid-soaked food in the stomach from making its way back into the esophagus. The stomach is a saclike organ located just beneath the diaphragm. Besides temporarily storing food, the stomach, shown in Figure 8 on the next page, also mechanically breaks down food and chemically unravels and breaks down proteins. Teach Bio 9C Demonstration Cut the legs off of an old pair of pantyhose. Place a tennis ball in the toe and tie off the other end. You can show the process of peristalsis by rhythmically squeezing the tennis ball from one end to the other. Remind students that this happens automatically after swallowing, and several “swallows” (boli) can travel down the esophagus at one time. English Language Learners LS Visual TAKS 2 Bio 10A Transparencies TT Teeth and Digestion Chapter 39 • Digestive and Excretory Systems 907 Teach, continued continued Figure 8 The stomach and accessory digestive organs. Many organs are involved in the complete breakdown of nutrients. Liver Eating Disorders TAKS 2 Bio 10A, 10B, (grade 11 only); Bio 11B, 11C Teacher’s Notes Eating disorders are a sensitive issue with teens.You may have a student with an eating disorder that has not yet been diagnosed. Be sure to address these issues openly and without judgment. Be prepared to direct students to a person or place where they can seek help. Discussion Ask students: What is the difference between anorexia nervosa and bulimia nervosa? (Anorexics do not eat sufficient nutrients. Bulimics eat, but purge their digestive system through vomiting or the use of laxatives.) Why does weight stay nearly constant for bulimics? (Because food is actually ingested, some nutrients are absorbed. If laxatives are the method of purging, the food has the chance to travel throughout the whole digestive system, just at a more rapid pace.) Should advertisers seek models with fuller figures to reduce the incidence of eating disorders? (Answers will vary. For example: Yes, people might feel better about themselves with less cultural emphasis on being thin.) Transparencies TT The Stomach and Accessory Digestive Organs Gallbladder Duodenum (small intestine) Pancreas When food enters the stomach, gastric juice is secreted by the cells that line the inside of the stomach. Gastric juice is a combination of hydrochloric (HIE droh klawr ihk) acid (HCl) and pepsin. The acid breaks the bonds in proteins and unfolds large protein chains into single protein strands. Pepsin , a digestive enzyme secreted by the stomach, cuts the single protein strands into smaller chains of amino acids. Pepsin is effective only in an acidic environment. The stomach mixes its contents by using peristaltic waves. Swallowed food can spend from 2 to 6 hours in the stomach. Your stomach secretes about 2 L (2.11 qt) of HCl Stomach every day, which creates a solution about 3 million times more acidic than your bloodstream. The hormone gastrin regulates the synthesis of HCl. Thus, HCl is made only when the pH in the stomach is higher than about 1.5. A coating of mucus protects the lining of the stomach from gastric acid. Bicarbonate in the stomach helps neutralize digestive fluids. Blood circulation in the stomach lining also helps protect stomach tissues. Eating Disorders TAKS 2 M illions of teens are on weight-reducing diets. Although maintaining a healthy body weight is important, obsessive dieting can lead to eating disorders. Eating disorders can disrupt lives and sometimes even result in death. Starving Oneself Anorexia nervosa is an eating disorder in which people starve themselves. Anorexics have an irrational fear of becoming fat and see themselves as much heavier than they really are. They shun food and may exercise for hours every day in an attempt to lose weight. Female anorexics may never mature sexually or may stop menstruating because they lose too much body fat, causing normal levels of sex hormones to fall. Their body temperature and pulse rate become abnormally low; their hair becomes thin and dry; and their resistance to infection drops. Bingeing and Purging Patients with bulimia engage in frequent episodes of bingeing (eating a large amount of food in a short time). After a binge, bulimics may purge by selfinduced vomiting or by using laxatives. Therefore, their weight stays fairly constant. Unlike anorexic patients, bulimics often recognize that their behavior is abnormal and often feel guilty, depressed, and helpless. The frequent purging removes salts from the body, which can eventually lead to muscle weakness, heart failure, and kidney disease. The vomiting gradually destroys tooth enamel results in unhealthy gums. and Help for People with Eating Disorders Little is known about what causes anorexia nervosa and bulimia. Many people believe that Western society’s emphasis on thinness in women is largely to blame. However, recent research suggests that genetic factors might also be involved. Both eating disorders can be managed with a combination of medical treatment, counseling, and family support. 908 Career pp. 908–909 Student Edition TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 10A, 10B Teacher Edition TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 4B, 10A, 10B TAKS Obj 4 IPC 9B TEKS Bio 3D, 4B, 10A, 10B, 11B, 11C TEKS Bio/IPC 2D TEKS IPC 9B, 9E 908 Counselor Counselors give clients moral support and an opportunity to discuss personal or work-related problems. Counselors may be professional social workers, psychologists, or community workers interested in helping people. Employers include treatment centers, hospital-based programs, or government agencies. Each state has its own Chapter 39 • Digestive and Excretory Systems requirements for counselors. In some states counselors must earn a certificate. Have students interview a counselor that works with persons with eating disorders such as anorexia or bulimia. Ask each student to compile a list of 10 questions and answers from the interview. Bio 3D The Small Intestine Food passes from the stomach into the small intestine when a sphincter between the two organs opens. The small intestine is a coiled tubular organ about 6 m (19.8 ft) long that is continuous with the stomach and that functions mainly in the digestion and absorption of nutrients. The word small refers to the small diameter of the small intestine as compared with the diameter of the large intestine—not to its length. Peristalsis mixes the food, which remains in the small intestine for about 3 to 6 hours. The first part of the small intestine, the duodenum (doo oh DEE nuhm), receives secretions from the pancreas, liver, and gallbladder, as shown in Figure 8. Cells that line the small intestine and the pancreas secrete digestive enzymes involved in completing the digestion of carbohydrates into monosaccharides, proteins into amino acids, and lipids into fatty acids and glycerol. Before fats can be digested by pancreatic enzymes called lipases (LIE pays uhs), the fats must first be treated with bile, a greenish fluid produced by the liver. Bile breaks up fat globules into tiny fat droplets, a process called emulsification (ee MUHL suh fih kay shuhn). The gallbladder, a green muscular sac attached to the liver, concentrates and stores bile until it is needed in the small intestine. Most absorption (passage of nutrients to the blood or lymph) occurs in the small intestine. The lining of the small intestine is covered with fine fingerlike projections called villi (singular form, villus). Villi, shown in Figure 9, are too small to see with the naked eye. In turn, the cells covering each villus have projections on their outer surface called microvilli. The villi and microvilli greatly increase the area available for absorption of nutrients. Sugars and amino acids enter capillaries in the villi and are carried in the blood to the liver for further metabolism. Fatty acids and glycerol enter lymphatic vessels in the villi and eventually enter the bloodstream. Demonstration You will need two beakers of tap water, a sugar cube, a crushed sugar cube, and two stirring rods. At the same time, drop the sugar cube and crushed sugar into two separate beakers. Stir rapidly and observe which sugar dissolves first. Ask students for an explanation. (The crushed sugar cube has more surface area, so it dissolves faster.) Relate this principle to the increase of surface area in the intestine brought about by the villi and microvilli. LS Verbal TAKS 1 Bio/IPC 2D; IPC 9E Using the Figure Have students look at the structure of the small intestine in Figure 9. Use two pieces of yarn to show how surface area increases with the number of villi. (This can be demonstrated on the overhead.) Make a circle with a short piece of yarn. Use a much longer piece of yarn to simulate villi inside of the shorter piece. When you compare the lengths of the yarn, it becomes clear that villi (and microvilli) significantly increase surface area. Figure 9 Villi in the small intestine Inside each villus are capillaries and lymphatic vessels where nutrients enter the bloodstream. Microvilli GENERAL Capillaries LS Visual TAKS 2 Bio 4B, 10A Activity Villus Lymphatic vessels Small intestine 909 IPC Benchmark Fact Explain to students that acids are substances that react with water to form hydronium ions, H3O. Since gastric juice contains hydrochloric acid, a strong acid, its pH is significantly below 7, it would have a sour taste, and it is corrosive. TAKS 4 IPC 9B (grade 11 only) MISCONCEPTION ALERT Digestion and Absorption Although some digestion occurs in the mouth and stomach, most chemical digestion occurs in the small intestine. All nutrient absorption into the bloodstream occurs in the small intestine, not the stomach. However, both alcohol and aspirin are absorbed from the stomach directly into the bloodstream, accounting for their fast-acting effects on the body. TAKS 2 Bio 4B Viewing Digestive Organs Provide students with a compound light microscope and prepared slides of several different digestive organs. You might want to include cross sections of tissue from the stomach, the small intestine, the liver, and the pancreas. Have students observe the specimens, compare the different cross sections, and make sketches of them. Encourage students to link the structures they observe with the functions of each organ. For example, students may relate the structure of villi to the function of nutrient absorption of the small intestine. English Language LS Visual Learners TAKS 2 Bio 4B, 10A, 10B, (grade 11 only) Transparencies TT Villi in the Small Intestine Chapter 39 • Digestive and Excretory Systems 909 The Large Intestine All components of food that are not for energy production (for example, cellulose) are considered wastes. The wastes move into the large intestine. The large intestine, or colon (KOH luhn), shown in Figure 10, is much shorter than the small intestine. However, the diameter of the large intestine is about three times larger than the diameter of the small intestine. The colon is not coiled like the small intestine. Instead, it is composed of three relatively straight segments. No digestion takes place in the colon. The volume of material that flows through the digestive system each day is large—about 10 L of food, drink, and secretions enter the small intestine. But the amount of material that leaves the body as waste is small. This is because almost all of the fluids and solids (about 90–95 percent) are absorbed during their passage through the small intestine. Mostly mineral ions and water are absorbed through the wall of the large intestine. Most of the colon’s contents are dead cells, mucus, digestive secretions, bacteria, and yeast. A thriving colony of bacteria live in the human colon. These microbes synthesize many compounds that your body needs and cannot get easily from the food you eat, including vitamin K and several B vitamins. In addition, bacteria aid in transforming and compacting the undigested materials into the final waste product, feces. The final segment of the large intestine is the rectum. Solids in the colon pass into the rectum as a result of peristalsis in the large intestine. From the rectum, the solid feces are eliminated from the body through the anus. Undigested material passes through the large intestine and is expelled through the anus in 12 to 24 hours. Balancing water absorption in the intestine is important. Wastes rushed through the large intestine before the remaining water is absorbed result in diarrhea (watery feces). When food remains in the colon for long periods of time, which causes much water to be absorbed, constipation (hard feces) results. Hard feces are difficult to pass. Teach, continued continued Teaching Tip GENERAL Enzymes and Nutrients Help students remember enzymes and the nutrients they break down straight by making a Graphic Organizer similar to the one at the bottom of this page. Remind students that the suffix –ase means “to break apart.” LS Visual Bio 9C SKILL BUILDER Graphing Provide students with the following average lengths of the digestive organs: esophagus—25 cm, stomach—25 cm, small intestine— 6 m, large intestine—1.5 m. Then have students prepare a bar graph or another graphic to compare the average lengths of each digestive organ listed. You might also want to have students measure and label the lengths using addingmachine tape or a skein of yarn and compare them to the illustration of the digestive system in this chapter. English Language LS Logical Figure 10 X ray of the large intestine (colon). Stretched out, the large intestine, which appears orange, is about 1 m (3.3 ft) long. Learners The Liver’s Role in Digestion The human liver, shown in Figure 8, is about the size of a football and weighs more than 1.4 kg (3.1 lb). It presses upward against the diaphragm and occupies the upper right side of the abdominal cavity. The liver plays several roles in digestion. The liver secretes bile, which aids in the emulsification of fats. Bile also promotes the absorption of fatty acids and the fat-soluble vitamins A, D, E, and K. Bile pigments (the products of hemoglobin breakdown) give bile a yellowish green color. Jaundice, a condition in which the eyes, skin, and urine become abnormally yellow, is a result of increased amounts of bile pigments in the blood. Jaundice often occurs as a result of hepatitis, an inflammation of the liver. IPC Benchmark Review To prepare students for the TAKS and accompany the discussion of digestion, have students Chemical Changes, TAKS 4 IPC 8A on p. 1052 of the IPC Refresher in the Texas Assessment Appendix of this book. 910 Graphic Organizer pp. 910–911 Student Edition TAKS Obj 1 Bio/IPC 2A TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 9C, 10A, 10B, 11C TEKS Bio/IPC 2A, 2C Teacher Edition TAKS Obj 1 Bio/IPC 2A, 2C TAKS Obj 2 Bio 10A, 10B TEKS Bio 3E, 9A, 9C, 10A, 10B, 11C TEKS Bio/IPC 2A, 2C 910 Use this graphic organizer with Teaching Tip on this page. Chapter 39 • Digestive and Excretory Systems Digestive enzymes amylase pepsin lipases starches into sugars large proteins into smaller proteins fats into fatty acids and glycerol mouth stomach intestine The Liver’s Role in Metabolism Digested food molecules in the bloodstream are transported to the liver. The liver stabilizes blood sugar by converting extra sugar to glycogen for storage. The liver then breaks down the glycogen when it is needed for energy. The liver also modifies amino acids. Fatsoluble vitamins and iron are stored in the liver. The liver monitors the production of cholesterol and detoxifies poisons. If the liver is unable to change a substance’s harmful form, it stores it. In this way, toxins, including heavy metals and pesticides, accumulate in the liver. The liver can also be damaged by viral infections, chronic drug or alcohol use, and traumatic injury. As a result of any of these, healthy liver cells are destroyed and replaced by scar tissue. The scarring of the liver is called cirrhosis (suh ROH sihs). www.scilinks.org Topic: Poisons Keyword: HX4142 The Function of Bile TAKS 1 Bio/IPC 2A, 2C; Bio 9A, 9C Skills Acquired Relating concepts, inferring conclusions, comparing Teacher’s Notes Detergents are made of molecules with hydrophobic and hydrophilic ends. The hydrophobic ends surround the grease and pull it toward the water, breaking up the grease. Modeling the Function of Bile You can use a detergent and cooking oil to simulate the effect bile has on breaking up (emulsifying) fats as part 2A 2C 9C TAKS 1 of digestion. Answers to Analysis 1. The oil spreads away from the water and the oil droplets associate. 2. The oil was broken up. 3. Detergent breaks up oil like bile breaks up fat. 4. They both increase surface area. For the bile this speeds up the breakdown of foods. Materials two 250 mL beakers, water, cooking oil, dish detergent, stirring rod, graduated cylinder Procedure Analysis 1. Label one beaker A and one beaker B. Fill each beaker halfway with water. 1. Describe how oil reacts with the water. 2. Add 10 mL of the cooking oil to each beaker. 2. Describe what happened to the oil when the dish detergent was added. 3. While stirring, slowly add 10 drops of dish detergent to beaker B only. 3. Compare the effect of dish detergent on oil with the effect of bile on fats. 4. Critical Thinking Inferring Conclusions Do the detergents and bile increase or decrease the surface area of oil? In the case of bile, how does this help the digestive process? Close Reteaching Section 2 Review Summarize the path a piece of cheese pizza would follow through the digestive system. Critical Thinking Applying Information 10A Relate the role of the mouth, stomach, small intestine, and large intestine in the digestion of 10A a piece of cheese pizza. Locate the area of the digestive system where nutrients are absorbed into the bloodstream. 10A 10B State how the liver and pancreas are involved 10A 10B in digestion. A person has a small intestine that has villi but a reduced number of microvilli. Would you expect this person to be underweight or overweight? 10A 11C Explain. TAKS Test Prep The enzyme pepsin is involved in the digestion of 9C A starches. C monosaccharides. B fats. D proteins. 1. mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum TAKS 2 Bio 10A 2. mouth—mechanical and chemical digestion of carbohydrates in the pizza; stomach— mechanical digestion and chemical digestion of the proteins in the pizza; small intestine— chemical digestion of the carbohydrates, proteins, and lipids in the pizza, and absorption; large intestine—reabsorption of water and compaction of waste TAKS 2 Bio 10A 3. small intestine TAKS 2 Bio 10A, 10B (grade 11 only) 4. Both the pancreas and the liver provide digestive enzymes. The liver also provides bile to TAKS 2 Bio 10A Quiz GENERAL 1. What muscular movements 911 Answers to Section Review Have students make flashcards with a digestive organ named on one side and its function on the other. Have students arrange them in order from mouth to anus and identify each as part of the digestive tract or as accessory organs. cause food to be passed through the digestive tract? (peristalsis) 2. What two organs are important in digestion but are not a part of the digestive tract? (liver and pancreas) TAKS 2 Bio 10A the small intestine, maintains blood sugar levels, modifies amino acids, stores vitamins and minerals, regulates cholesterol production, and detoxifies poisons. TAKS 2 Bio 10A, 10B (grade 11 only) 5. The person would be underweight—more Alternative food will pass out as waste. The person will GENERAL Assessment probably also be malnourished. Refer to the clothesline from the TAKS 2 Bio 10A; Bio 11C Demonstration on the first page of 6. A. Incorrect. Starches are this section. Remove the labels, digested by amylase enzymes. B. Incorrect. and have students identify the parts Fats are digested by lipases. C. Incorrect. of the digestive system and what Monosaccharides are already broken down happens to food in each of those into absorbable units. D. Correct. Proteins are parts. digested by the enzyme pepsin. Bio 9C Chapter 39 • Digestive and Excretory Systems 911 Section 3 Section 3 Excretion Teach, continued continued Objectives Overview Before beginning this section review with your students the objectives listed in the Student Edition. This section introduces students to how metabolic wastes are removed from the blood and excreted from the body. Students will also learn about the causes and consequences of kidney damage. Bellringer Tell students that the blood must be cleaned regularly. Then ask students to speculate, without looking in the textbook, how the body cleans blood. Once students have written a description of the cleaning process, allow them to check their answers against their textbook. LS Verbal Motivate Activity ● Identify major wastes produced by humans and the organ or tissue where they are eliminated from the body. 10A TAKS 2 ● Relate the role of nephrons to the filtering of blood in the kidneys. 10A TAKS 2 ● Summarize how nephrons form urine. 10A TAKS 2 ● Describe the path of urine through the human urinary system. 10A TAKS 2 ● Predict how kidney damage might affect homeostasis and threaten life. 10A 10B 11A Key Terms excretion urea nephron urine ureter urinary bladder urethra Water and Metabolic Wastes Cleaning up, though not always a pleasant chore, must be done to maintain a healthy living environment. In the same way, our bodies must get rid of wastes to maintain health. Food residues are eliminated from the body in the form of feces. Other wastes produced as a result of metabolic reactions that occur in the body must also be eliminated. For example, water and carbon dioxide are produced during cellular respiration. During the metabolism of proteins and nucleic acids, a toxic nitrogen-containing waste, ammonia, is formed. The body must remove wastes. It must also maintain osmotic balance and stable pH by either excreting or conserving salts and water. Excretion is the process that rids the body of toxic chemicals, excess water, salts, and carbon dioxide while maintaining osmotic and pH balance. The organs involved in excretion are shown in Figure 11. Carbon dioxide (and some water vapor) is transported to your lungs by the circulatory system and excreted every time you exhale. Excess water is excreted through the skin in sweat and through the kidneys in urine. In the liver, ammonia is converted to a much less toxic nitrogen waste called urea (yoo REE uh), which is then carried by the bloodstream to the kidneys, where it is removed from the blood. Organs of Excretion GENERAL Observing Sweat Have a volunteer put his or her hand in a clear plastic bag and tape it loosely to the wrist. Study the bag after 10 or 15 minutes. What do students observe? (tiny droplets of moisture on the bag) Explain that sweat is constantly evaporating from the skin. If time permits, have the student rub some of their own sweat onto individual slides and observe salt crystals. Red dye will make the crystals easier to see. LS Kinesthetic TAKS 2 Bio 4B, 10A; Bio 11B Lungs Figure 11 Organs of excretion. The lungs, the kidneys, and the skin all function as excretory organs. The main excretory products are carbon dioxide, water, and nitrogen wastes (urea). 1 The lungs excrete carbon dioxide and water vapor in exhaled air. Kidneys The kidneys excrete nitro2 gen wastes, salts, water, and other substances in urine. Skin The skin excretes water, 3 salts, small amounts of nitrogen wastes, and other substances in sweat. 912 Chapter Resource File pp. 912–913 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B, 11A Teacher Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B, 10A, 10B TEKS Bio 4B, 10A, 10B, 11B, 11C TEKS Bio/IPC 2C 912 • Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL Transparencies TT Bellringer TT Organs of Excretion Chapter 39 • Digestive and Excretory Systems Planner CD-ROM • Reading Organizers • Reading Strategies • Supplemental Reading Guide Microbe Hunters The Kidneys The kidneys are extremely important organs because of their role in regulating the amount of water and salts contained in blood plasma. The kidneys are a pair of bean-shaped, reddish brown organs located in the lower back. Each kidney is the size of a small fist. The body has to maintain a certain level of salts in the blood plasma and in the fluid surrounding cells, or serious harm to the body’s cells and organ systems can result. Blood Filters The word glomerulus is from the French gloméruli, meaning “a compact cluster.” Knowing this makes it easier to remember that the glomerulus is a compact cluster of capillaries within a nephron. Each kidney is a complex organ composed of roughly 1 million microscopic blood-filtering units called nephrons (NEHF rahns), as shown in Figure 12. Nephrons are tiny tubes in the kidneys. One end of a nephron is a cup-shaped capsule surrounded by a tight ball of capillaries that filters wastes from the blood, retains useful molecules, and produces urine. Three different phases occur as the blood flows through a nephron: filtration, reabsorption and secretion. Kidneys Ask students to point to the location of their kidneys. They are located in the middle of the back, near the spinal cord, just under the last ribs. English Language Review how passive transport processes (blood pressure) account for the filtration of blood in the nephron. Have students locate where filtration occurs in the nephron shown in Figure 12. (in Bowman’s capsule) Review how active transport processes account for the reabsorption of materials as blood passes through the nephron and both passive and active processes are involved in secretion. Have students locate where reabsorption and secretion occur in the nephron shown in the figure. (the renal tubules) Point out that because of active transport, the kidney has an extremely high energy requirement, even higher than that of the heart, when comparing their relative weights. The kidneys filter out toxins, urea, water, and mineral salts from the blood as fluid passes through the microscopic filtering units called nephrons. Glomerulus Renal tubule Bowman's capsule LS Visual Blood vessels TAKS 2 Bio 4B, 10B (grade 11 only) Collecting duct SKILL To renal vein Filtration Reabsorption Ureter Loop To ureter (urine) Secretion 913 REAL WORLD CONNECTION Exercise and sweating deplete the body of many necessary materials. Sports drinks are beverages that consist of water with about a 6 percent concentration of carbohydrates and electrolytes (salts, particularly sodium). Sports drinks are thought to improve performance in athletes who are exercising for more than Learners Using the Figure Figure 12 Kidneys and nephrons Renal vein (filtered blood) Teaching Tip LS Kinesthetic Filtration Filtration begins at the cup-shaped capsule called Bowman’s capsule. Within each Bowman’s capsule an arteriole enters and splits into a fine network of capillaries called a glomerulus (gloh MEHR yoo luhs). The glomerulus acts as a filtration device. The blood pressure inside the capillaries forces a fluid composed of water, salt, glucose, amino acids, and urea into the hollow interior of the Bowman’s capsule. This fluid is called filtrate. Blood cells, proteins, and other molecules too large to cross the membrane remain in the blood. Renal artery (blood with wastes) Teach 90 minutes because the carbohydrates maintain blood sugar (glucose) levels during exercise when muscle glycogen (stored glucose) levels start to run critically low. The electrolytes in the sports drink are supposed to allow the carbohydrates and water in the drink to be absorbed into the body faster. Bio 11C BUILDER GENERAL Math Skills Tell students that the heart pumps about 5 L (2.6 gal) of blood per minute. Keeping in mind that one-fourth of this volume travels to the kidneys, have students calculate the volume of blood that is filtered each day. (5 L/min 60 min/hr 24 h 0.25 1,800 L per day) Ask students to calculate how much of the blood is actually filtered if about 55–60 percent of the 5 L of blood is plasma, and only 18–20 percent of the plasma, water, and small solutes are actually filtered out of the blood and into the nephron capsule. (1,800 L 0.55 0.18 178.2 L are actually filtered per day.) LS Logical TAKS 1 Bio/IPC 2C Transparencies TT Kidneys and Nephrons Chapter 39 • Digestive and Excretory Systems 913 Real Life Teach, continued continued Real Life Answers TAKS 3 Bio 4D; Bio 11C Answers will vary. Researchers have found nanobacteria in kidney stones. It is thought that the bacteria cause kidney stones in genetically susceptible humans. The mineral shells that cause calcium deposits in the body form around the bacteria. Nanobacterial infections can be treated with antibiotics. Teaching Tip GENERAL Water Treatment Plant Ask the manager from a water treatment plant to come and discuss the processes the plant uses to remove substances from water. Have students write a short report that relates this information to how the kidney removes substances from the blood. LS Auditory Bio 3D Demonstration Kidney stones are painful. Kidney stones form from crystallized mineral and urea salts. The crystals form “stones” that block the passage of urine and result in extreme pain. Ultrasound waves can be used to crush kidney stones until they are small enough to pass with the urine. Finding Information Research the role of nanobacteria in the formation of kidney 4D, 11C TAKS 3 stones. TAKS 1 Bio/IPC 1A Urine Formation The urine that is excreted from the body is formed from the water, urea, and various salts that are left after the absorption and secretion processes. Collecting ducts receive fluid from several nephron segments and empty the urine into areas of the kidneys that lead to the ureters. Ureters (yoo REET uhrs) are tubes that carry the urine from the kidney to the urinary bladder. The collecting duct removes much of the water from the filtrate that passes through it. As a result, human urine can be very concentrated. In fact, it can be as much as four times more concentrated than blood plasma is. Elimination of Urine Figure 13 The organs of urinary excretion. Urine exits the kidneys by way of two ureters that empty into a storage organ called the urinary bladder. Urine exits the body through the urethra. GENERAL Obtain a pig or sheep kidney from a local butcher. Cut the kidney in half lengthwise. Have students identify the obvious structures. Ask students if they can identify the smell. (ammonia) Ask students how kidneys are prepared before cooking. (You must soak the kidney in salt water to release the ammonia before cooking it.) Students should wear disposible gloves if they are to handle the kidney. Ask students to wash their hands after the demonstration. LS Visual Reabsorption and Secretion Reabsorption begins when the filtrate passes from the Bowman’s capsules into the renal tubules— long, narrow tubes connected to Bowman’s capsules. Renal tubules bend at their center, which forms a loop. As the filtrate passes through the renal tubules, the tubules extract from the filtrate a variety of useful molecules, including glucose, ions, and some water. These substances reenter the bloodstream through capillaries that wrap around the tubule. This arrangement prevents these molecules from being eliminated from the body in the urine. Some substances can pass from the blood into the filtrate in a process called secretion. Kidney Ureter Urinary bladder Urethra The ureters, shown in Figure 13, have smooth muscle in their walls. The slow, rhythmic contractions of this muscle move the urine through the ureters. The ureters direct the urine into the urinary bladder, a hollow, muscular sac that stores urine. The urinary bladder gradually expands as it fills. The average urinary bladder can hold up to about 0.6 L (0.63 qt) of urine. The urinary bladders of males tend to be larger than those of females. Muscular contractions of the bladder force urine out of the body. Urine leaves the bladder and exits the body through a tube called the urethra (yoo REE thruh). A healthy adult eliminates from about 1.5 L (1.6 qt) to 2.3 L (2.4 qt) of urine a day, depending on the volume of fluid he or she consumes. In females the urethra lies in front of the vagina and is only about 2.5 cm (1 in.) long. Such a short length makes it easy for bacteria and other pathogens to invade the female urinary system, which explains why females are more prone to urinary infections than males are. There is no connection between the urethra and the genital (reproductive) system in females. In males the urethra passes through the penis. In males, both sperm and urine exit the body through the urethra. The tube that carries sperm from the testes eventually merges with the urethra. 914 IPC Benchmark Mini-Lesson pp. 914–915 Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TAKS Obj 3 Bio 4D TEKS Bio 4B, 4D, 10A, 10B, 11C Teacher Edition TAKS Obj 1 Bio/IPC 1A TAKS Obj 3 Bio 4D TAKS Obj 4 IPC 9B TEKS Bio 3D, 3E, 4D, 11B, 11C TEKS Bio/IPC 1A, 3C TEKS IPC 9B 914 Biology/IPC Skills TAKS 4 IPC 9B (grade 11 only) Daily Fluid Intake It is ironic that as food Relate the concentrations of ions in a solution to conscious as Americans are, they often pay little chemical properties including pH. attention to the other side of the coin—their Activity Tell the students they can calculate the fluid intake. In fact, people can survive without hydronium ion concentration ([H3O]) of stomach acid food much longer than they can survive without (hydrochloric acid (HCl)) when they know the pH of water. On average, an adult needs 1.5–3 L of stomach acid is about 2.0. Write the following on the board: [H3O] antilog(pH). Students can use their water per day, some of it being supplied by calculators to find the answer. foods with high water content such as lettuce, [H3O] 10–pH 10–2, therefore the concentration of watermelon, and citrus fruits. Any combination [H3O] is 0.01 molar solution. of foods and beverages that provides the needed amount of water is acceptable, but most nutritionists recommend 6–8 glasses of liquid a day over and above the amount contained in food. Bio 11C Chapter 39 • Digestive and Excretory Systems The elimination of urine from the body through the urethra is called urination. When the bladder fills with urine, stretch receptors in the bladder’s wall send nerve impulses to the spinal cord. In response, the spinal cord returns impulses to the bladder and urethra simultaneously. These impulses cause contraction of the bladder’s muscular walls and relaxation of the rings of muscle closing off the urethra. The bladder then empties its contents through the urethra. In older children and adults, the brain overrides this urination reflex, which delays the release of urine until a convenient time. www.scilinks.org Topic: Kidney Diseases Keyword: HX4109 Activity Interview Have students interview a person who has had kidney stones or talk to a physician about them. Students should ask about the causes of kidney stones and the treatment. If possible, allow students to bring in a kidney-stone specimen for the class to observe. Damage to the Kidneys Because of the vital role played by the kidneys in maintaining homeostasis, diseases affecting these organs may eventually threaten life. If one kidney is lost in an accident or by disease, the other may enlarge and do the work of both. Nephrotic syndrome refers to a number of signs and symptoms that result from damage to the glomeruli, which leads over time to kidney failure. The most common causes of kidney failure are infection, diabetes, high blood pressure, and damage to the kidneys by the body’s own immune system. Because of their function in excretion, kidneys often are exposed to hazardous chemicals that have entered the body through the lungs, skin, or gastrointestinal tract. Household substances that, in concentration, can damage kidneys include paint, varnishes, furniture oils, glues, aerosol sprays, air fresheners, and lead. When kidneys fail, toxic wastes, such as urea, accumulate in the plasma, and bloodplasma ion levels increase to dangerous levels. If both kidneys fail, there are only two treatment options. Kidney Dialysis Kidney dialysis, also called hemodialysis (HEE moh die AL uh sihs), is a procedure for filtering the blood by using a dialysis machine, as shown in Figure 14. A dialysis machine, just as the nephrons in the kidney, sorts small molecules in the blood, keeping some and discarding others. Dialysis machines are sometimes used for kidneys that are damaged but either will eventually heal or be replaced by a kidney transplant. GENERAL LS Auditory Teaching Tip Concept Map Have students define the new terms in this section and use the terms to construct a concept map. Make sure the maps contain appropriate words and phrases linking the terms. LS Verbal Bio 3E Figure 14 Hemodialysis. Hemodialysis has prolonged the lives of many people with damaged or diseased kidneys. The dialysis machine functions like a kidney in that it filters urea and excess ions from the blood. Transparencies TT Kidney Dialysis Kidney Transplants A more permanent solution to kidney failure is transplantation of a kidney from a healthy donor. A major problem with kidney transplants is common to all organ transplants— rejection of the transplanted organ by the recipient’s immune system. Recall that the cells of your body have “self-markers,” or antigens, on their surfaces that identify the cells to your immune system so it will not attack them. The combination of these antigens displayed on your body’s cells is as unique as your fingerprints. 915 did you know? Urine Output High blood pressure, drinking lots of fluids, and cold weather promote increased urine output. High blood pressure increases the filtration pressure in the kidneys. Increased fluid consumption raises the blood pressure and decreases the output of antidiuretic hormone (ADH). Cold weather increases the metabolic rate and thus increases the rate of filtration. Low blood pressure, reduced intake of fluids, and hot weather decrease urine output for the converse reasons. Bio 11B Career Dialysis Technician Dialysis technicians operate dialysis machines and monitor and record a patient’s weight and vital signs before, during, and after dialysis. Have students research the career of a dialysis technician and prepare a short report. The report should include a job description, training required, employer, growth potential, starting salary, and job satisfaction. Bio/IPC 3C, Bio 3D Chapter 39 • Digestive and Excretory Systems 915 Only identical twins have the same set of antigens. The more closely related two individuals are, the more likely they are to have common antigens. This is why tissue transplants are more likely to succeed if the donor and recipient are closely related. But even in close matches, there is some chance of transplant rejection. To reduce chances of rejection, the recipient is treated with drugs that suppress the activity of the immune system. Kidney Dialysis TAKS 2 Bio 4B, 10A, 10B To demonstrate osmosis, bring in some dialysis tubing and show students how permeable it is. Pour a starch solution into the tubing, which is immersed in an iodine and water solution. The iodine will diffuse into the tubing, turning the starch solution blue-black. Discussion Ask students why dialysis machines are less effective than kidneys. (Machines do not dialyze constantly as the body does. Levels of salt, protein and water cannot be closely regulated with a machine.) Close Reteaching Have students return to their statements in the Opening Activity for this chapter. Ask students if their opinions have been confirmed or changed in any way. TAKS 2 Bio 4B Quiz GENERAL 1. What are the three organs of excretion? (lungs, kidneys, skin) 2. What tubelike structures are the main blood-filtering units of the kidneys? (nephrons) TAKS 2 Bio 10A Alternative Assessment Dialysis machine Exploring Further Catheter Kidney Dialysis TAKS 2 People whose kidneys are damaged cannot filter their blood. Kidney dialysis is one option for artificially filtering the blood. In kidney dialysis, tubes called catheters are surgically inserted into an artery and a vein, usually on a forearm. The catheters are equipped with valves. Every few days the catheters are connected to a dialysis machine, as shown to the right. Blood Is Filtered Blood passes from the patient’s artery into the dialysis machine. Inside the machine, the blood travels through many hollow tubes, each of which is surrounded by a thin, permeable membrane. Waste materials and ions that have accumulated in the person’s blood diffuse through the membrane into a fluid that has the same makeup as normal blood plasma and is free of wastes. The filtered blood is then returned to the person’s vein. Dialysis is not a permanent solution to kidney failure. A single healthy kidney can meet all of the homeostatic needs of the body, but no dialysis machine can. Dialysis patients must carefully manage their salt, protein, and water intake Student Edition TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 10A TAKS Obj 2 Bio 10B TEKS Bio 4B, 10A, 10B, 11A Teacher Edition TAKS Obj 1 IPC 3B TAKS Obj 2 Bio 4B, 10A, 10B TEKS Bio 3B, 3E, 4B, 10A, 10B TEKS IPC 3B 916 Fresh dialysis solution Compressed air Used dialysis solution because the dialysis machine cannot regulate these blood components as well as the kidney can. www.scilinks.org Topic: Kidney Dialysis Keyword: HX4108 Critical Thinking Applying Information is produced and excreted. A doctor has just informed a patient that his urine contains a high sugar concentration. Explain why 10A 11A this may indicate damaged kidneys. 10A 10B Relate the following terms to the formation of 10A urine: filtration, reabsorption, and secretion. Name the liquid stored inside the collecting duct 10A from the body. 10A TAKS Test Prep The substances that are removed from the body by the excretory system 10A 10B are carried to the kidneys by the A nervous system. C circulatory system. B respiratory system. D digestive system. 916 Answers to Section Review 1. Carbon dioxide is produced during cellular respiration and excreted through the lungs. TAKS 2 Bio 10A, 10B (grade 11 only) pp. 916–917 Solution Identify how the carbon dioxide in your body Summarize how urine is stored and eliminated Ask students to summarize the function of the urinary system, using as many science terms as possible. TAKS 2 Bio 10A Blood Section 3 Review of a nephron. GENERAL Semipermeable membrane 2. filtration—kidneys filter blood, removing water, salt, glucose, amino acids, and urea; reabsorption—useful molecules and water are reabsorbed by the bloodstream; secretion— wastes and toxic materials pass from blood into filtrate TAKS 2 Bio 10A 3. urine TAKS 2 Bio 10A 4. Urine is stored in the bladder. When stretch receptors in the bladder send nerve impulses to the spinal cord, the bladder muscles relax and urination occurs. TAKS 2 Bio 10A Chapter 39 • Digestive and Excretory Systems 5. Sugar should be reabsorbed by the bloodstream in the kidney. TAKS 2 Bio 10A; Bio 11A 6. A. Incorrect. The nervous system does not carry waste products to the kidney. B. Incorrect. The respiratory system can carry metabolic waste (carbon dioxide) but carries it to the lungs. C. Correct. Wastes to be removed from the body are carried to the kidney by the circulatory system. D. Incorrect. The digestive system does not carry waste products to the kidney for removal. TAKS 2 Bio 10A, 10B (grade 11 only) Study CHAPTER HIGHLIGHTS ZONE Key Concepts Alternative Assessment Key Terms Section 1 1 Your Body’s Need for Food ● Food and beverages provide the nutrients and water required by the body for growth, energy, repair, and maintenance. ● Carbohydrates and lipids provide most of the body’s energy. Proteins are normally used for making other proteins. ● The USDA food guide pyramid graphically summarizes the daily recommended servings from each food group. ● Vitamins enhance the activity of enzymes and regulate the release of energy. Minerals are used to make certain body structures and substances, for normal nerve and muscle function, to maintain osmotic balance, and for enzyme function. ● Water acts as a lubricant, solvent, and coolant, and as a support medium for cells and tissues. nutrient (900) digestion (900) calorie (900) vitamin (904) mineral (905) Section 2 2 Digestion ● Teeth break down food into smaller pieces. Amylase begins the breakdown of starch to sugars. The stomach stores and mechanically breaks down food. Stomach acid and pepsin chemically break down proteins. ● Most chemical digestion occurs in the small intestine with the help of secretions from the pancreas, liver, and gallbladder. ● Usable compounds are absorbed into capillaries or lymphatic vessels in villi. Compounds not absorbed are eventually excreted as feces. ● The liver releases bile, helps to maintain blood sugar levels, and detoxifies poisons. GENERAL Commercial diet programs are big business. Have students research commercial diet programs and report how each claims to bring about weight loss. Encourage students to look for information on how these programs might affect either the digestive or excretory systems. For example, a highprotein diet places added stress on the liver and kidneys, because the body must produce and then rid itself of more urea, secondary to higher nitrogen intake. Have students present their research in a multimedia format. LS Verbal amylase (907) esophagus (907) pepsin (908) lipase (909) villus (909) colon (910) TAKS 1 IPC 3B; Bio 3B Chapter Resource File • Science Skills Worksheet • Critical Thinking Worksheet • Test Prep Pretest GENERAL • Chapter Test GENERAL GENERAL Section 3 3 Excretion ● The skin, lungs, and kidneys are specialized to excrete wastes. ● Nephrons in the kidneys filter wastes from the blood. Most of the water, some of the salts, and all of the sugar and amino acids in the filtrate are reabsorbed into the bloodstream. The water, urea, and salts that remain in the nephron are eliminated as urine. ● Kidney dialysis and organ transplants are treatment options when both kidneys fail. excretion (912) urea (912) nephron (913) urine (914) ureter (914) urinary bladder (914) urethra (914) 917 Answer to Concept Map The following is one possible answer to Performance Zone item 15 on the next page. Nutrients most absorbed in small intestine some absorbed in large intestine include Bio 3E carbohydrates proteins digested by digested by enzymes pepsin hydrochloric acid in secreted by secreted by saliva pancreas stomach lipids vitamins emulsified by bile secreted by liver secreted into protected by mouth mucus minerals TAKS Test Prep • The Science TAKS Prep Appendix in this book provides integrated biology and IPC TAKS practice. • The Holt Science TAKS Practice Workbook provides a review of biology, chemistry, and physics concepts tested on the grades 10 and 11 science TAKS. Chapter 39 • Digestive and Excretory Systems 917 Performance ZONE CHAPTER 39 ANSWERS Using Key Terms 1. c Bio 9A 2. d TAKS 2 Bio 10A 3. c TAKS 2 Bio 10A; Bio 9C 4. a TAKS 2 Bio 10A 5. a. absorption—the other terms refer to processes involved in the filtering of blood by nephrons. b. villi—the other terms refer to structures in the kidney Understanding Key Ideas 6. c TAKS 2 Bio 10A; Bio 9A 7. a Bio 11C 8. b Bio 9C 9. d TAKS 2 Bio 10A, 10B (grade 11 only) 10. d TAKS 2 Bio 10A 11. c TAKS 2 Bio 10A 12. A. grains, 6–11 servings a day; B. fruits, 2–4 servings a day Bio 11C 13. In anorexia the levels of sex hormones may fall, the body temperature and pulse rate become abnormally low, the hair becomes thin and dry, and resistance to infections drops. In bulimia the teeth, gums, and esophagus often are damaged, and muscle weakness, heart failure, and kidney disease can occur. Bio 11C CHAPTER REVIEW 8. The body needs vitamins because they a. supply energy. b. activate enzymes. c. function as enzymes. d. act as hormones. Using Key Terms 1. Proteins are made up of a. fatty acids. b. glycerol. c. amino acids. d. monosaccharides. 9A 9. Which substance is not a waste eliminated from the body through the kidneys? a. urea c. salts b. water d. oxygen 2. During digestion, food passes through the mouth, esophagus, stomach, _______, and large intestine. 10A a. pancreas c. gallbladder b. lungs d. small intestine 3. Which of the following correctly pairs 10. The _______ are involved in excretion. a. kidneys and stomach b. liver and pancreas c. pancreas and kidneys d. kidneys and lungs 10A 10A move from a. the filtrate to the blood. b. the urethra to the bladder. c. the blood to the filtrate. d. the bladder to the urethra. 4. Nutrients in the small intestine enter the 12. Identifying Information Identify the food groups represented by A and B. Indicate the number of servings that should be 11C eaten daily for A and B. bloodstream by passing through 10A a. villi. b. gastric pits. c. glomeruli. d. nephrons. A 5. For each set of terms below, choose the B term that does not belong and explain why it does not belong. a. absorption, filtration, secretion, reabsorption b. nephron, villi, glomerulus, renal tubule Understanding Key Ideas 6. The primary function of carbohydrates is to 9A 10A a. break down molecules. b. aid in digestion. c. supply the body with energy. d. regulate the flow of acid. 7. Food from the _______ food group should 11C 13. Describe the body changes 11C caused by anorexia and bulimia. 14. Summarize how a kidney 10A 10B 11C dialysis machine filters blood. 15. Concept Mapping Make a concept map that shows how nutrients are digested. Try to include the following words in your map: carbohydrates, proteins, lipids, enzymes, saliva, pancreas, stomach, bile, liver, small 2C 3E intestine, and large intestine. 918 14. Blood moves through tubes composed of semipermeable membranous material, which are bathed in fluid with the same composition as clean plasma. Wastes diffuse out of the tubes and into the “plasma.” The filtered blood circulates into the patient’s body. TAKS 2 Bio 10A, 10B; 11C 918 10A 10B 11. During secretion in the kidney, substances the enzymes with the food molecules they digest? 9C 10A a. lipases, starches b. amylases, fats c. lipases, fats d. pepsin, starches be eaten in the greatest abundance. a. grains b. fats, oils, and sweets c. vegetables d. milk, yogurt, and cheese pp. 918–919 Review and Assess TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 10A, 10B TAKS Obj 3 Bio 4D, 12B TEKS Bio 3E, 4D, 9A, 9C, 10A, 10B, 11A, 11C, 12B TEKS Bio/IPC 2C 9C 15. One possible answer to the concept map is found at the bottom of the Study Zone page. TAKS 1 Bio/IPC 2C; Bio 3E Chapter 39 • Digestive and Excretory Systems Assignment Guide Section 1 2 3 Questions 1, 6–8, 12–13, 15 2–4, 15 5a–b, 9–11, 14 Critical Thinking Alternative Assessment Critical Thinking 16. Evaluating Conclusions The length 20. Finding Information Compile a list of 16. Answers will vary. Students who agree might argue that water is more readily available so that their need to conserve water is not as critical as in humans. of the looped tubule in a nephron varies among mammal species. A friend believes the looped tubules of mammals that live in the water would be shorter than those found in humans. Do you agree or disagree? Explain. 10A 10B agencies and programs in your community that work with teens who have eating disorders. Develop a fact sheet for each eating disorder and include them with your list. 11C 21. Communicating Write an article that needs an acidic environment for optimal absorption. What kinds of foods would you recommend be combined with calcium-rich foods in order to maximize absorption? 11C 18. Determining the Validity of a Claim A Bio 11C 22. Relating Concepts Look at books that friend believes a vegetarian diet would decrease his intake of saturated fat and cholesterol. Do you agree or disagree? 10A 11C Explain. 19. Relating Concepts Describe the symbiotic role of bacteria in the human intestine. 17. acidic foods such as tomatoes, oranges, and other citrus fruits discusses diuretics (substances that increase urine excretion) for your school or local newspaper. Emphasize diuretics that most people have heard of, such as the caffeine in coffee and soft drinks. 10A 11A 17. Recommending Information Calcium 4D 12B TAKS 2 Bio 10A, 10B (grade 11 only) describe the cultures and customs of other nations. Find information relating to ideas about body shape, ideal body weight, and eating habits for at least five different countries. Describe how these ideas differ 11C from those in the United States. 18. Answers will vary. Students who agree might point out that in most nonvegetarian diets, most fats and cholesterol come from animal products. TAKS 2 Bio 10A; Bio 11C 19. Bacteria live in the human colon where they synthesize vitamin K and several B vitamins, and aid in the elimination of feces. TAKS 3 Bio 4D, 12B TAKS Test Prep Alternative Assessment Use the food label below and your knowledge of science to answer questions 1–3. Nutrition Facts Amount /serving Total fat 1g % DV* 1% Serv. size 2 oz Sat. fat 0 g 0% (56 g / –18 box) Servings per container 8 Cholesterol 0 mg 0% Calories 210 Fat Cal. 10 *Percent Daily Values (DV) are based on a 2,000 Calorie diet. Sodium 0 mg 0% Amount /serving % DV* Total carb. 43 g 14% Dietary fiber 2 g 8% Sugars 3 g Protein 6 g Vitamin A 0% • Vitamin C 0% • Calcium 2% • Iron 10% Thiamin 30% • Riboflavin 10% • Niacin 15% 1. What is the main function of dietary 11C fiber? A to provide energy B to provide materials for making enzymes C to help food pass through the digestive tract D to maintain osmotic balance 2. A healthful diet should provide no more than 30 percent of a day’s calories from fats. Approximately what percentage of the 11C calories in pasta come from fats? F 1 percent H 10 percent G 5 percent J 14 percent 3. A food is considered to be a good source of a vitamin or mineral if it provides at least 10 percent of that vitamin or mineral. Based on that criterion, pasta is a good 11C source of A vitamin A, vitamin C, calcium, and iron. B vitamin A, vitamin C, riboflavin, and niacin. C iron, thiamin, riboflavin, and niacin. D calcium, iron, thiamin, and riboflavin. 20. Answers will vary. Students may start by contacting your local public health authority or mental health agency. Bio 11C 21. Answers will vary. Students’ lists might include caffeine, parsley, juniper, buchu leaves, uva ursi, and other herbs, as well as prescription drugs. TAKS 2 Bio 10A; 11A 23. Answers will vary. Bio 11C Test If time permits, take short mental breaks during the test to improve your concentration. 919 1. A. Incorrect. Providing energy is a function of carbohydrates. B. Incorrect. Providing materials for making enzymes is a function of proteins. C. Correct. The main function of dietary fiber is to help food pass through the digestive tract. D. Incorrect. Maintaining osmotic balance is a function of minerals. Bio 11C 2. F. Incorrect. The percentage of fat that a pasta serving contributes to the Daily Values is 1%, not the percentage of its total calories that are from fats. G. Correct. To determine the percentage of calories from fat, the number of fat calories (10) should be divided by the total calories (210), which equals about 5%. H. Incorrect. The fat calories per serving is 10, which is not the percentage of its total calories that are from fats. J. Incorrect. The percentage of carbohydrates that a serving contributes to the Daily Values is 14%, not the percentage of its total calories that are from fats. Bio 11C 3. A. Incorrect. Iron is the only nutrient in this list that meets the criterion; the others are less than 10%. B. Incorrect. Riboflavin and niacin meet the criterion, but the other nutrients are at less than 10%. C. Correct. All these nutrients meet the criterion of at least 10% provided by the pasta. D. Incorrect. These nutrients meet the criterion except for calcium, which is only 2%. Bio 11C Chapter 39 • Digestive and Excretory Systems 919