Reading Essentials for Biology Glencoe (794133), страница 98
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Even thoughthe human body cannot digest cellulose(also known as fiber), cellulose is importantin the diet. It helps in the elimination ofwastes. Sources of cellulose include bran,beans, and lettuce.Includes butter,oils, salad dressingsand soft drinksFatSugarHow does your body use fats?Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Fats are an essential nutrient. They provide energy for your body. Fats also areessential building blocks of the cell membrane.
Fats help synthesize hormones,protect body organs against injury, andinsulate the body from cold.Meats, nuts, and dairy products containfats. Cooking oils are another source ofdietary fat. In the digestive system, fats breakdown into fatty acids and glycerol. They areabsorbed by the villi of the small intestine.Some fatty acids eventually end up in theliver. The liver converts them to glycogen orstores them as fat throughout your body.How does your body use proteins?The body uses proteins in many ways. Enzymes, antibodies,many hormones, and substances that help the blood clot are allproteins.
Proteins form parts of your muscles. Many cell structures, including cell membranes, are formed of proteins.During digestion, proteins are broken down into amino acids.The amino acids are absorbed by the small intestine, and theyenter the bloodstream. They are carried through the bloodstreamto the liver. The liver can change amino acids to fats or to glucose.Both fats and glucose can be used for energy. Your body uses aminoacids for energy only if other energy sources have been used up.Most amino acids are absorbed by cells and used for protein synthesis. The human body needs 20 different amino acids for proteinsynthesis.
The body can make only 12 of these, so the other 8amino acids must come from the food that you eat. Sources ofessential amino acids include meats, dried beans, whole grains,eggs, and dairy products.READING ESSENTIALS2. What role do fats play inmaintaining the humanbody?________________________________________________________________________Chapter 35431NameDateClassSection35.2Nutrition, continuedHow does your body use minerals and vitamins?________________________________________________________________________How does your body use water?Between 45 and 75 percent of your body mass is water.
Wateris the most abundant substance in your body. Water helps chemical reactions take place in your body. It is necessary for breakingdown foods during digestion. Water is a solvent. Oxygen andnutrients from food cannot enter your cells unless they have beenfirst dissolved in water.Water helps your body maintain its internal temperaturebecause water absorbs and releases heat slowly. The body containsso much water, it takes a lot of added energy to raise your bodytemperature. Every day your body loses about 2.5 L of waterthrough exhalation, sweat, and urine.
Therefore, you need todrink enough water every day to replace the water that is lost.4. Evaluate Why wouldteenagers need moreCalories per day thanadults?________________________________________________________________________432Chapter 35Calories and MetabolismA calorie is the amount of heat that is needed to raise the temperature of 1 mL of water by 1ºC.
The energy content of food ismeasured in Calories. The term Calories, written with a capitalletter C, represents a kilocalorie, or 1000 calories. Some foodscontain more Calories than other foods. 1 g of fat generally contains nine Calories. 1 g of carbohydrate or protein generallycontains only four Calories.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.3. What is the differencebetween vitamins andminerals?A mineral is an inorganic substance that serves as a buildingmaterial for your body. Minerals take part in chemical reactions inyour body.
They make up about four percent of your total bodyweight. Most minerals are found in your skeleton. Minerals arenot used as an energy source.Vitamins are organic nutrients that help maintain growth andmetabolism. Your body needs only small amounts of them. Thereare two main groups of vitamins. One group is water-soluble,which means that they dissolve in water. Water-soluble vitaminscannot be stored in the body and must be included regularly inthe diet. The other main group of vitamins is fat-soluble.
Thesevitamins dissolve in fats. Fat-soluble vitamins can be stored in thebody’s liver. Excessive amounts of fat-soluble vitamins in the liver,however, can be poisonous.Vitamin D, a fat-soluble vitamin, is synthesized in your skin.The bacteria in your large intestine synthesize vitamin K andsome B vitamins. The rest of the vitamins that your body needsmust be taken in through your food.NameDateClassSection35.2Nutrition, continuedThe number of Calories needed each day depends on a person’smetabolism. Metabolism is the rate at which energy is burned.A person’s body mass, age, gender, and level of physical activityalso affect how much energy is used.
Males usually need moreCalories per day than females. Teenagers use more Calories thanadults, and active people use more Calories than inactive people.What is the relationship between Caloriesand health?Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.If a person takes in more Calories than his or her body canmetabolize, or burn, the extra energy is stored as body fat. Theperson gains weight. If a person eats fewer Calories than the bodycan metabolize, some of the body’s stored energy is used.
Thatperson will lose weight.Many Americans are overweight. Being overweight increasesthe risk of developing health problems including high blood pressure, diabetes, and heart disease. Underweight people can havehealth problems, too. These can include anemia, fatigue, and adecreased ability to fight off infections and diseases.◗ After You ReadMini GlossaryCalorie: unit of heat used to measure energycontent of food, each Calorie represents akilocalorie, or 1000 calories; a calorie is theamount of heat that is needed to raise thetemperature of 1 mL of water by 1ºCmineral: an inorganic substance found mainly inthe skeleton that serves as a building material for your bodyvitamin: organic nutrients required in smallamounts to maintain growth andmetabolism1.
Read the terms and their definitions in the Mini Glossary above. On the lines below, write asentence for each term that describes the functions of the term.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________READING ESSENTIALSChapter 35433NameDateClassSection35.2Nutrition, continued2.
Use the web diagram below to list ways that each item helps a healthy body function.CarbohydratesWaterFatsNutritionVitaminsProteinsCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.MineralsVisit the Glencoe Science Web site at science.glencoe.com to find yourbiology book and learn more about nutrition.434Chapter 35READING ESSENTIALSNameDateClassSection35.3 The Endocrine SystemSC.F.1.4.6 The student knows that the separate parts of the body communicate with each other using electrical and/orchemical signals. SC.F.1.4.7 The student knows that organisms respond to internal and external stimuli.
Also coversSC.F.1.4.1, SC.F.1.4.5, SC.F.1.4.8◗ Before You ReadThe endocrine system releases chemicals called hormones directly into the bloodstream. These hormones control many of the body’s functions. One important hormone is the human growth hormone.What role do you think this hormone serves in helping the body function? When do you think thishormone is most important to human development? Write your response on the lines below.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Control of the BodyInternal control of the body is directed by two systems.
In thissection you will learn about the endocrine system. Later, you willlearn about the other system, the nervous system. The functionsof all body systems are controlled by the interaction between thenervous system and the endocrine system. As you will recall, inmammals, a gland is a cell or a group of cells that secretes fluid.The endocrine system is made up of a series of glands, calledendocrine glands. Endocrine glands release chemicals directlyinto the bloodstream. These chemicals relay information to otherparts of the body.Identify MainIdeas As you read, highlightthe glands of the endocrinesystem.
Use another colorto highlight what theseglands do.How do the nervous and endocrinesystems interact?The endocrine system and the nervous system work togethermuch of the time. The two systems maintain homeostasis in thebody. As you will recall, homeostasis is the ability of a livingorganism to maintain internal equilibrium or conditions thatenable it to survive. Because there are two control systems withinthe human body, the nervous system and the endocrine system,coordination is needed between the two. The hypothalamus(hi poh THA luh mus) is the part of the brain that connects theendocrine system and the nervous system. The hypothalamusreceives messages from other areas of the brain.
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