5. Foods that you eat provide chemical elements that are needed to make carbon compounds in your body.

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1 CHATER 14 Carbon Chemistry LEON 3 Compounds of Life What do you think? Read the two statements below and decide whether you agree or disagree with them. lace an A in the Before column if you agree with the statement or a D if you disagree. After you ve read this lesson, reread the statements to see if you have changed your mind. Before tatement After Key Concepts What are biological molecules? What are some groups of carbon compounds found in living organisms? 5. Foods that you eat provide chemical elements that are needed to make carbon compounds in your body. 6. Carbohydrates should be totally eliminated from a healthful diet. Biological Molecules Many of the objects you use, such as CDs, DVDs, sandwich bags, plastic bowls, and combs, are made of synthetic polymers. Your body also contains polymers. You learned that polymers in nature are called natural polymers. Cells, tissues, and organs in your body and bodies of other living organisms contain natural polymers. Individual cells of organisms contain polymers that carry genetic information and pass this information to new cells. The chemical energy stored in your muscles is a polymer, too. Meat, potatoes, rice, and grains contain polymers produced by living organisms. All of these natural polymers are called biological molecules. A biological molecule is a large organic molecule in any living organism. Biological molecules help determine the structure and function of many different body parts. They also provide the energy needed to run, to pedal a bicycle, and for the many other activities that you do. The chemical elements that make up these molecules come from the foods you eat and the air you breathe. Identify Main Ideas As you read, highlight the main idea in each paragraph. This will help you review later. Key Concept Check 1. Describe What are biological molecules? Reading Essentials Carbon Chemistry 261

2 Make a four-column chart to record information about biological molecules and their functions in the human body. roteins Biological Carbohydrates Molecules Nucleic Acids Lipids Visual Check 2. Describe what the R stands for on the molecule. roteins What do spider webs, the leaves and roots of plants, and peacock feathers have in common? They contain natural polymers called proteins. Much of your body is made of proteins as well. Your hair, muscles, blood, organs, immune system, and fingernails are all made up of proteins. A protein (ROH teen) is a biological polymer made of amino acid monomers. An amino acid (uh MEE noh A sud) is a carbon compound that contains the two functional groupsamino and carboxyl. Amino Acid Chains Amino acids link together and form long chains. Amino acids are monomers that form proteins. Look at the basic chemical structure of an amino acid in the figure below. The R represents a side chain of molecules that can differ. This is called the variable side chain. There are 20 different side chains. This means that there are 20 different amino acids that can link and form proteins. Amino acid Amino group Variable side chain H R H N C C O H O H Reading Check 3. Define What are essential amino acids? Hydrogen atom Carboxyl group roteins contain hundreds of amino acids linked together in a chain. ome proteins chains form helical, or spiral, shapes. roteins and the Human Body roteins are important to your body. Of the 20 different amino acids, the human body can make 11 of them. The other nine must be included in the foods that you eat. These nine amino acids are often called essential amino acids. They are in foods such as fish, dairy products, beans, and meat. Carbohydrates When you eat foods such as pasta and sugary snacks, you are eating carbohydrates. A carbohydrate (kar boh HI drayt) is a group of organic molecules that includes sugars, starches, and cellulose. These are natural polymers that contain carbon, hydrogen, and oxygen atoms. Carbohydrates are a source of energy in cells. 262 Carbon Chemistry Reading Essentials

3 ugars imple sugars, such as glucose and fructose, usually contain five or six carbon atoms. The carbon atoms can be arranged in a ring or in a straight chain. Your cells can easily break apart simple sugars, which provide quick energy. Honey contains glucose. Many fruits contain fructose. Your blood contains glucose. Glucose and fructose combine chemically and form a sugar called sucrose. ucrose, also known as table sugar, is used to sweeten foods and beverages. tarch and Cellulose When simple sugar molecules form chains, they form polymers called complex carbohydrates. tarch and cellulose are complex carbohydrates made of glucose monomers. The chemical bonds in starches take longer to break apart than simple sugars do. They provide energy over a longer period. Human digestive systems cannot break the bonds in cellulose, but the digestive systems of animals, such as cows and horses, can. Nucleic Acids A biological polymer that stores and transmits genetic information is a nucleic acid (new KLEE ihk A sud). Genetic information includes instructions for cells on how to make proteins, produce new cells, and transfer genetic information. Genetic information determines how you look and how your body functions. The monomer in a nucleic acid polymer is called a nucleotide. Each nucleotide monomer contains a phosphate group, a sugar, and a nitrogen-containing base. All nucleotides contain the same phosphate group. However, the sugar and nitrogen base can vary in nucleic acids. The elements your body needs to make nucleic acids come from the foods you eat. DNA Two common nucleic acids, DNA and RNA, control cellular function and heredity. DNA is deoxyribonucleic acid (dee AHK sih rib oh noo klay ihk A sud). DNA is a spiralshaped molecule that looks like a twisted zipper. Each DNA monomer contains the five-carbon sugar deoxyribose. Deoxyribose and phosphate groups form the outside of the zipper. airs of nitrogen-containing basesadenine (A) and thymine (T), or cytosine (C) and guanine (G)form the teeth of the zipper. 4. Identify Name three foods you eat that are sources of carbohydrates. ACADEMIC VOCABULARY transmit (verb) to pass, to send, to forward, or to convey Reading Essentials Carbon Chemistry 263

4 Visual Check 5. how the nitrogen bases in the figure of the DNA molecule. Circle each one. The nitrogencontaining bases form the teeth of the zipper. C A G T G Key Concept Check 6. Identify What are two groups of carbon compounds found in living organisms? The sugar and phosphate groups form the backbone of the zipper. RNA RNA is ribonucleic acid. It contains the five-carbon sugar ribose. RNA is usually single-stranded, not double-stranded like DNA. RNA contains the nitrogen bases adenine, cytosine, guanine, and uracil. RNA uses the information stored in DNA to make the proteins that a cell needs to function. Lipids Lipids are biological molecules, but they are not polymers. A lipid is a type of biological molecule that includes fats, oils, hormones, waxes, and components of cellular membranes. Lipids have two major functions in living organisms. They store energy and make up cellular membranes. Look at the molecule of DNA in the figure above. This spiral-shaped molecule is often called a double helix. 264 Carbon Chemistry Reading Essentials

5 aturated and Unsaturated Lipids There are two main groups of lipidssaturated and unsaturated. aturated lipids contain only single bonds. They contain carbon bonded to the maximum number of hydrogen atoms possible. tearic acid, a saturated lipid found in bacon, is shown in the figure below. Unsaturated lipids contain at least one double bond. If an unsaturated lipid has one double bond, it is called monounsaturated. If it has more than one double bond, it is called polyunsaturated. Oleic acid is an unsaturated lipid found in olive oil. It s structure is shown in the figure below.. Unsaturated O C CH CH CH 3 HO O HO aturated C CH 3 Lipids in Organisms Lipids, such as fats and oils, store energy for organisms. Lipids also control what enters and leaves individual cells. These lipids are called phospholipids because they contain a phosphate functional group in their structure. hospholipids form the cell membrane around individual cells. This two-layer membrane controls what enters and leaves a cell, such as nutrients, wastes, and water. Visual Check 7. Describe the difference between saturated and unsaturated lipids. 8. Explain Why are lipids an important part of any diet? Reading Essentials Carbon Chemistry 265

6 Mini Glossary amino acid (uh MEE noh A sud): a carbon compound that contains the two functional groupsamino and carboxyl biological molecule: a large organic molecule in any living organism carbohydrate (kar boh HI drayt): a group of organic molecules that includes sugars, starches, and cellulose lipid: a type of biological molecule that includes fats, oils, hormones, waxes, and components of cellular membranes nucleic acid (new KLEE ihk A sud): a biological polymer that stores and transmits genetic information protein (ROH teen): a biological polymer made of amino acid monomers 1. Review the terms and their definitions in the Mini Glossary. Choose one biological molecule and explain why that molecule is important to life. 2. Fill in the chart below to compare the two types of nucleic acids. DNA RNA ugar ribose tructure Nitrogen bases Function What do you think double strand Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind? ConnectED adenine, uracil, cytosine, guanine transmits genetic information 3. What are proteins? Explain why proteins are important to the human body. Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson s resources. END OF LEON 266 Carbon Chemistry Reading Essentials