Chemistry in Biology PDF - Atoms, Elements, and Compounds

chapter 6 Chemistry in Biology section...

chapter 6 Chemistry in Biology section 1 Atoms, Elements, and Compounds Before You Read -!). )DEA Matter is composed of tiny On the lines below, describe how you think chemistry relates particles called atoms. to living things. Then read the section to learn about the What You’ll Learn chemical building blocks of matter. the particles that make up atoms the difference between covalent bonds and ionic bonds about van der Waals forces Read to Learn Read for Understanding Atoms As you read this section, Chemistry is the study of matter. Matter is anything that has highlight any sentences that mass and takes up space. All organisms are made of matter. you do not understand. After you finish the section, reread the Atoms are the building blocks of matter. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. highlighted sentences. Atoms are made up of neutrons, protons, and electrons, as shown in the figure below. The nucleus is the center of the atom where the neutrons and protons are located. Protons are positively charged particles (p+). Neutrons are particles that have no charge (n0). Electrons are negatively charged particles (e–) that are located outside the nucleus. Electrons move around the nucleus in energy levels. The atom’s structure is the result of the attraction between protons and electrons. Atoms contain an equal number of protons and electrons. As a result, the overall charge of an atom is zero. %NERGY LEVELS.UCLEUS  PROTONS P Picture This.UCLEUS  NEUTRONS N 1. Identify the number of  PROTON P electrons in the outermost  NEUTRONS N energy level of the oxygen atom.  ELECTRON E  ELECTRONS E (YDROGEN ATOM /XYGEN ATOM Reading Essentials Chapter 6 Chemistry in Biology 55  Elements An element is a pure substance that cannot be broken down into other substances. The periodic table of elements organizes information about elements in rows, called periods, and columns, called groups. A periodic table is located inside the back cover of this workbook. Each block includes the element’s name, number, symbol, and mass. Living things are composed mainly of three elements—carbon, hydrogen, and oxygen. How are isotopes identified? Atoms of the same element have the same number of protons and electrons but sometimes different numbers of neutrons. 2. Apply Another carbon Atoms of the same element with different numbers of neutrons isotope has six protons and are called isotopes. Isotopes are identified by adding the seven neutrons in its nucleus. number of protons and neutrons. Carbon-12 has six protons What do you think this carbon isotope is called? and six neutrons. Carbon-14 has six protons and eight neutrons. What makes an isotope radioactive? Changing the number of neutrons in an atom can cause the nucleus to decay, or break apart. When a nucleus breaks apart, it gives off radiation. Isotopes that give off radiation are called radioactive isotopes. All living things contain the radioactive Picture This isotope carbon-14. Scientists know the half-life of carbon-14, 3. Draw Conclusions or the amount of time it takes for half of carbon-14 to decay. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. Table salt is a compound By finding how much carbon-14 remains in an object, scientists made of sodium and can calculate the object’s age. chlorine. Could you separate the sodium from the chlorine by crushing Compounds the salt crystals? Explain. When two or more elements combine, they form a compound. Each compound has a chemical formula made up of the chemical symbols from the periodic table. For example, water is made of hydrogen (H) and oxygen (O). Its formula is H2O. The table below lists characteristics of compounds. Characteristics of Compounds Example Always formed from a specific combination of Water is always a ratio of two hydrogen atoms and elements in a fixed ratio one oxygen atom: H2O. Chemically and physically different than the Water has different properties than hydrogen and elements that comprise them oxygen. Cannot be broken down into simpler compounds or Passing water through a filter will not separate the elements by physical means hydrogen from the oxygen. Can be broken down by chemical means An electric current can break water down into hydrogen and oxygen. 56 Chapter 6 Chemistry in Biology Reading Essentials  Chemical Bonds The force that holds substances together is called a chemical bond. Chemical bonding involves electrons. Electrons travel around the nucleus of an atom in energy levels. Each energy level can hold only a certain number of electrons. The first energy level, which is closest to the nucleus, can hold up to two electrons. The second level can hold up to eight electrons. A partially-filled energy level is not as stable as a full or 4. Apply Study the oxygen an empty energy level. Atoms become more stable by losing atom illustrated below. Is electrons or attracting electrons from other atoms. This the second energy level of the oxygen atom full? electron activity forms chemical bonds between atoms. The Explain. forming of chemical bonds stores energy. The breaking Nucleus of chemical bonds releases energy for an organism’s life processes—growth, development, and reproduction. The two Energy level main types of chemical bonds are covalent and ionic. How do covalent bonds form? Electrons A covalent bond forms when atoms share electrons. The figure below shows the covalent bonds between oxygen and Oxygen atom hydrogen to form water. Each hydrogen (H) atom has one electron in its outer energy level, and the oxygen (O) atom has six. The outer energy level of oxygen is the second level, so it can hold up to eight electrons. Oxygen has a strong tendency to fill the energy level by sharing electrons from the two Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. nearby hydrogen atoms. Hydrogen also has a strong tendency to share electrons with oxygen to fill its outer energy level. Two covalent bonds form a water molecule. Most compounds in living things are molecules. A molecule is a compound in which the atoms are held together by covalent bonds. Covalent bonds can be single, double, or triple. A single bond shares one pair of electrons. A double bond shares two pairs of electrons. A triple bond shares three pairs of electrons. Picture This / 5. Label the first energy level and second energy level in  P the oxygen atom. Include  N in each label the number of electrons required to fill the level. ( P P ( #OVALENT 7ATER BOND MOLECULE Reading Essentials Chapter 6 Chemistry in Biology 57  How do ionic bonds form? Recall that atoms do not have an electric charge. Also recall that an atom is most stable when its outer energy level is either empty or full. To become more stable, an atom might give up electrons to empty its outer energy level. Or, the atom might accept electrons to fill the outer energy level. An atom that has given up or gained one or more electrons becomes an ion and carries an electric charge. For example, the outer energy level of sodium (Na) has one electron. Sodium can become more stable if it gives up this electron to empty the energy level. When it gives up this electron, the neutral sodium atom becomes a positively charged sodium ion (Na+). Chlorine (Cl) needs just one electron to fill its outer energy level. When it accepts an electron from another atom, chlorine becomes a negatively charged ion (Cl–). An ionic bond is an electrical attraction between two 6. Describe what happens to an atom’s electric charge oppositely charged ions. When sodium gives its electron to if the atom gives up an chlorine, the positively charged sodium ion (Na+) is attracted electron. to the negatively charged chlorine ion (Cl–). The ionic bond between them forms the ionic compound sodium chloride (NaCl), or table salt. Ions in living things help maintain homeostasis as they travel in and out of cells. Ions also help transmit signals that Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. enable you to see, taste, hear, feel, and smell. Some atoms give up or accept electrons more easily than other atoms. The elements identified as metals in the periodic table tend to give up electrons. The elements identified as nonmetals tend to accept electrons. van der Waals Forces Electrons travel around the nucleus randomly. The random movement can cause an unequal distribution of electrons around the molecule. This creates temporary areas of slightly positive and negative charges. Attractions between these positive and negative regions hold molecules together. These attractions between molecules are called van der Waals forces. These forces are not as strong as covalent and ionic bonds, but they play a key 7. Identify the substances role in biological processes. For example, attractions between that are held together by positive and negative regions hold water molecules together. As van der Waals forces. (Circle a result, water can form droplets. Note that van der Waals forces your answer.) a. atoms are the attractive forces between water molecules. They are not b. molecules the forces between the atoms that make up water. 58 Chapter 6 Chemistry in Biology Reading Essentials  chapter 6 Chemistry in Biology section 2 Chemical Reactions Before You Read -!). )DEA Chemical reactions allow On the lines below, explain why you think rust forms on living things to grow, develop, metal. Then read the section to learn the role of chemical reproduce, and adapt. reactions in living things. What You’ll Learn the parts of a chemical reaction how energy changes relate to chemical reactions the importance of enzymes in organisms Read to Learn 3TUDY #OACH Create a Quiz After you Reactants and Products read this section, create a five- Chemical reactions occur inside your body all the time. question quiz from what you You digest food. Your muscles grow. Your cuts heal. These have learned. Then, exchange quizzes with another student. functions and many others result from chemical reactions. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. After taking the quizzes, review A chemical reaction is the process by which atoms or your answers together. groups of atoms in substances are reorganized into different substances. Chemical bonds are broken and formed during chemical reactions. For example, rust is a compound called iron oxide. It forms when oxygen in the air reacts with iron. What was once silver and shiny becomes dull and orange-brown. Other clues that a chemical reaction has taken place include the production of heat or light, and formation of gas, liquid, or solid. How are chemical equations written? Scientists express chemical reactions as equations. On the left Picture This side of the equation are the starting substances, or reactants. 1. Describe how this On the right side of the equation are the substances formed general chemical equation during the reaction, or the products. An arrow is between these would be expressed in words. two parts of the equation. You can read the arrow as “yield” or “react to form.” The general form of a chemical equation is shown below. Reactants Products Reading Essentials Chapter 6 Chemistry in Biology 59  Why must chemical equations balance? The following chemical equation describes the reaction between hydrogen (H) and oxygen (O) to form water (H2O). Picture This 2H2 ⫹ O2 2H2O 2. Label the subscripts and the coefficients in this Matter cannot be created or destroyed in chemical reactions. equation after you read the This is the principle of conservation of mass. Therefore, mass discussion on this page. must balance in all chemical equations. This means that the number of atoms of each element on the reactant side must equal the number of atoms of the same element on the product side. In our example, the number of H atoms on the left side must equal the number of H atoms on the right side. The same must be true of O atoms. The larger 2 to the left of the element H is called a coefficient. Coefficients are used to balance chemical equations. If no coefficient or subscript appears with an element, both are assumed to be 1. To see that the above equation is balanced, multiply the coefficient by the subscript for each element. Then add up the total number of atoms of each element. Follow along in the equation above as you read the analysis below. Reactant side: 2 (coefficient of H) ⫻ 2 (subscript of H) ⫽ 4 H atoms Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. 1 (coefficient of O) ⫻ 2 (subscript of O) ⫽ 2 O atoms Product side: 2 (coefficient of H) ⫻ 2 (subscript of H) ⫽ 4 H atoms 2 (coefficient of O) ⫻ 1 (subscript of O) ⫽ 2 O atoms The equation has the same number of H atoms on both sides. Take Notes Make a three-tab It also has the same number of O atoms on both sides. No Foldable from a sheet of notebook paper. As you read, mass has been gained or lost. The equation balances. record what you learn about reactants, products, and the energy required to start a Energy of Reactions chemical reaction. Energy is required to start a chemical reaction. The minimum amount of energy needed for reactants to form products in a Reactants chemical reaction is called the activation energy. For example, a candle will not burn until you light the wick. The flame Products from a match provides the activation energy for the candle wick to react with oxygen in the air. Some reactions need Energy higher activation energy than others. 60 Chapter 6 Chemistry in Biology Reading Essentials  How does energy change in chemical reactions? Chemical reactions can be exothermic or endothermic. In exothermic reactions, energy is released in the form of heat or light. As a result, the energy of the product is lower than the energy of the reactants. In endothermic reactions, energy is absorbed. As a result, the energy of the product is higher than the energy of the reactants. 3. Explain why the energy Enzymes of the product might be Some chemical reactions occur slowly in a laboratory because lower than the energy of the reactants. the activation energy is high. To speed up the chemical reaction, scientists use catalysts. A catalyst is a substance that lowers the activation energy needed to start a chemical reaction. A catalyst does not increase how much product is made, and it does not get used up in the reaction. In living things, special proteins called enzymes are biological catalysts. Enzymes speed up the rate of chemical reactions in the body. Like all catalysts, enzymes are not used up by the chemical reaction. They can be used again. Also, most enzymes act in just one type of reaction. For example, the enzyme amylase is found in saliva. Amylase helps begin the process of food digestion in the mouth. The figure below shows how an enzyme works. The Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. reactants that bind to the enzyme are called substrates. The specific location where a substrate binds on an enzyme is called the active site. The substrate and active site are shaped to fit together exactly. Only substrates shaped to fit the active site will bind to the enzyme. The bond between the enzyme and substrates creates the enzyme-substrate complex. This complex helps to break bonds in the reactants and form new bonds, changing the substrates into products. The enzyme then releases the products. Enzymes are the chemical workers in cells. The actions of enzymes enable cell processes that supply energy. Factors such as pH and temperature affect enzyme activity. 3UBSTRATE !CTIVE SITES 0RODUCT Picture This 4. Label each of the three parts of this process with a brief description of what the part shows. 3UBSTRATE %NZYME %NZYME SUBSTRATE 0RODUCT COMPLEX Reading Essentials Chapter 6 Chemistry in Biology 61  chapter 6 Chemistry in Biology section 3 Water and Solutions -!). )DEA Before You Read The properties of water make it well-suited to help maintain Have you ever stirred a spoonful of a powdered drink into homeostasis in an organism. water? On the lines below, describe what happened to the What You’ll Learn powder. Then read the section to learn the properties of why water is a good solvent different types of mixtures. the differences between suspensions and solutions how acids differ from bases Read to Learn Restate the Main Point Highlight the main point in each Water’s Polarity paragraph. Then restate each Earlier you learned that water molecules are formed by main point in your own words. covalent bonds that link two hydrogen (H) atoms to one oxygen Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. (O) atom. The electrons in a water molecule are attracted more strongly to an oxygen atom’s nucleus. As a result, the electrons in the covalent bond are not shared equally. The electrons spend more time near the oxygen nucleus than near the hydrogen nuclei, as shown in the figure below. Note that the water molecule has a bent shape. This shape and the unequal distribution of electrons result in oppositely charged regions. The oxygen end has a slightly negative charge. The hydrogen end has a slightly positive charge. Picture This 3LIGHTLY 1. Label the H and O atoms. POSITIVE ENDS Then label each electron with the symbol for a negative charge (⫺). Most negative charges are close to the nucleus of which atom? 3LIGHTLY 7ATER NEGATIVE END MOLECULE 62 Chapter 6 Chemistry in Biology Reading Essentials  Why is polarity important? Molecules that have an unequal distribution of charges are called polar molecules. Polarity means having two opposite poles, or ends. A magnet has polarity. When the opposite poles of a magnet are close to each other, they attract. In the same way, when oppositely charged regions of polar molecules are close together, they attract each other. In water, the attraction is called a hydrogen bond. A hydrogen bond is a weak interaction involving a hydrogen atom and a fluorine, oxygen, or nitrogen atom. The hydrogen bonds between water molecules are illustrated by dotted lines in the diagram below. ) ) Picture This 0 0 ) ) 2. Circle each water molecule in this diagram. Remember, 0 a water molecule is made ) ) ) ) up of two H atoms and one 0 0 O atom. Hydrogen bonds ) )ZESPHFO ) link the water molecules CPOE together. How many water molecules are shown in this diagram? Mixtures with Water When you make a fruit-flavored drink, you dissolve drink powder in water. It does not react with water to form a new product. A mixture has been created. A mixture is Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. a combination of two or more substances in which each substance keeps its individual characteristics and properties. What is a homogeneous mixture? A homogeneous (hoh muh JEE nee us) mixture has the same composition throughout. A solution is another name for a homogeneous mixture. A solution has two parts: a solvent and a solute. A solvent is a substance in which another substance is dissolved. A solute is the substance that is dissolved in the solvent. In the fruit-flavored drink, water is the solvent and drink powder is the solute. How does a heterogeneous mixture differ? 3. Apply Are coins in your In a heterogeneous mixture, the parts remain distinct—that pocket a homogeneous is, you can identify the individual parts. For example, in a mixture or heterogeneous salad, you can tell the lettuce from the tomatoes. mixture? Explain. Sand mixed with water is a suspension—a type of heterogeneous mixture. Over time, the particles in a suspension will settle to the bottom. Paint is a heterogeneous mixture called a colloid, whose particles do not settle out. Reading Essentials Chapter 6 Chemistry in Biology 63  How do acids differ from bases? Water’s polarity enables many solutes to dissolve easily in water. The human body is about 70 percent water and contains many solutions. When a substance containing hydrogen is dissolved in water, the substance might release a hydrogen ion (H+), as illustrated in the figure below. Substances that release hydrogen ions when dissolved in water are called acids. The more hydrogen ions released, the more acidic the solution. Substances that release hydroxide ions (OH–) when 4. Identify the property of water that makes water a dissolved in water are called bases. The more hydroxide ions good solvent. released, the more basic the solution. 3UBSTANCE WITH ( ION 7ATER ( ( ( ( Picture This !CIDIC SOLUTION 5. Apply Suppose you want "ASIC SOLUTION to make the acid solution in /( this figure more acidic. Add /( /( drawings that would result /( in a more acidic solution. 3UBSTANCE WITH /( ION How do buffers affect pH? The measure of concentration of H+ in a solution is called Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. pH. Scientists use a pH scale like the one below to compare the strengths of acids and bases. Water is neutral and has a pH of 7.0. Acidic solutions have more H+ and have pH values lower than 7. Basic solutions have more OH– and have pH values higher than 7. To maintain homeostasis, H+ levels must be controlled. Buffers are mixtures that can react with acids or bases to keep the pH within a certain range. Picture This 3ODIUM HYDROXIDE .A/( 6. Determine which (OUSEHOLD AMMONIA ,EMON JUICE VINEGAR solutions are acidic and 5RINE HEALTHY LAKE /RANGE JUICE COLA.ORMAL RAINWATER %XAMPLES which are basic. Draw a 'REAT 3ALT ,AKE 3TOMACH ACID /VEN CLEANER 3OAPY WATER "AKING SODA "ATTERY ACID "LOOD TEARS circle around the buffer. 0URE WATER 4OMATOES 3EAWATER "ANANAS                P( 6ALUE.EUTRAL )NCREASINGLY ACIDIC )NCREASINGLY BASIC 64 Chapter 6 Chemistry in Biology Reading Essentials  chapter 6 Chemistry in Biology section 4 The Building Blocks of Life Before You Read -!). )DEA Organisms are made up of You have probably heard about DNA— the “genetic code.” On carbon-based molecules. the lines below, describe what you think DNA does. Then read What You’ll Learn the section to learn about DNA and the other compounds that the four major families of make up all living things. biological macromolecules the functions of each group of biological macromolecules Read to Learn 3TUDY #OACH Make an Outline Make Organic Chemistry an outline of the information Almost all biological molecules contain the element you learn in this section. Start carbon. For this reason, all life is considered carbon-based. with the headings. Include the Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. boldface terms. Organic chemistry is the study of organic compounds—the compounds that contain carbon. In the figure below, notice that carbon has four electrons in its outer energy level. Recall that the second energy level can hold eight electrons. Therefore, a carbon atom can form four covalent Picture This bonds with other atoms. Carbon atoms can bond with each 1. Calculate What other, forming a variety of organic compounds. These organic percentage of the carbon compounds can take the form of straight chains, branched atom’s second energy level is filled? chains, and rings, as illustrated in the figure below. Carbon compounds are responsible for the diversity of life on Earth. 3TRAIGHT CHAIN MOLECULES "RANCHED MOLECULES 2ING MOLECULES #ARBON Reading Essentials Chapter 6 Chemistry in Biology 65  Macromolecules Macromolecules are large molecules that are formed by joining smaller molecules together. Macromolecules are also called polymers. Polymers are made from repeating units of identical or nearly identical compounds called monomers. The monomers are linked together by a series of covalent bonds. The four major groups of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. The table below summarizes the functions of each group. Picture This Biological Macromolecules 2. Draw Conclusions Group Function To what group of macromolecules do you Carbohydrates stores energy think DNA belongs? provides structural support Lipids stores energy provides steroids waterproofs coatings Proteins transports substances speeds reactions provides structural support provides hormones Nucleic acids stores and communicates genetic Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. information What roles do carbohydrates play in biology? Carbohydrates are composed of carbon, hydrogen, and oxygen with a ratio of one oxygen and two hydrogen atoms for each carbon atom: CH2O. Short chains of carbohydrates are monosaccharides (mah nuh SA kuh ridz), or simple sugars. A disaccharide (di SA kuh rid) is two monosaccharides linked together. Longer carbohydrate chains are called polysaccharides. 3. Contrast monosacc- Carbohydrates serve as energy sources for organisms. Also, harides, disaccharides, and carbohydrates provide structural support in the cell walls polysaccharides. of plants, fungi, and in the hard shells of shrimp, lobsters, and some insects. What is the main function of lipids? Lipids are molecules made mostly of carbon and hydrogen. Fats, oils, and waxes are all lipids. The main function of lipids is to store energy. A lipid called a triglyceride (tri GLIH suh rid) is called a fat when solid and an oil when liquid. Plant leaves are coated with lipids called waxes to prevent water loss. 66 Chapter 6 Chemistry in Biology Reading Essentials  Saturated and Unsaturated Fats When the carbon atoms in a fat cannot bond with any more hydrogen atoms, the fat is a saturated fat. The carbon atoms of unsaturated fats can bond with more hydrogen atoms. Phospholipids A lipid called a phospholipid is responsible for the structure and function of the cell membrane. Lipids do not dissolve in water. This characteristic enables lipids to serve as barriers in biological membranes. Steroids Cholesterol and hormones are types of steroids, 4. Identify the key another group of lipids. In spite of its bad reputation, characteristic of lipids cholesterol provides the starting point for other important that enables them to keep unwanted substances lipids, such as the hormones estrogen and testosterone. from penetrating cell membranes. What compounds make up proteins? A protein is made of small carbon compounds called amino acids. Amino acids are made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Amino Acids There are 20 different amino acids. Proteins are made of different combinations of all 20 amino acids. Covalent bonds called peptide bonds join amino acids together to form proteins. Protein Structure A protein’s amino acid chain folds into Picture This a three-dimensional shape. The figure below shows two basic 5. Label Add these Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. descriptive labels to the protein shapes—the helix and the pleat. A protein might appropriate protein shape contain many helices, pleats, and folds. Hydrogen bonds help in the figure: folded paper the protein hold its shape. and spiral. ( # # / ( / ( / ( / ( /. # #. # # #. # # #. # # #. ( # # #.... # # # # # ( #. / ( ( ( ( / / / / / #. (YDROGEN # ( BONDS / # ( / # ( / # ( / # ( /. # # ( #. #. #. #. #. #. #. #.. # # # # / ( / ( / ( / ( / # ( # #. ( # / 0LEATED SHEET #. / # ( /. # # (. / # # # (. ( # /. / (ELIX Reading Essentials Chapter 6 Chemistry in Biology 67  Protein Function Proteins are involved in nearly every function of your body. Your muscles, skin, and hair are made of proteins. Your cells contain about 10,000 different proteins 6. Draw Conclusions that serve many functions. They What protein function listed here suggests that most provide structural support; enzymes are proteins? transport substances inside the cell and between cells; communicate signals within the cell and between cells; speed up chemical reactions; control cell growth. What roles do nucleic acids play in organisms? Nucleic acids are the fourth group of biological macromolecules. Nucleic acids are complex macromolecules that store and transmit genetic information. Repeating subunits, called nucleotides, make up nucleic acids. Nucleotides are composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus. All nucleotides have the three units shown in the figure below—a phosphate, a nitrogenous base, and a sugar. To form a nucleic acid, the sugar of one nucleotide bonds to the phosphate of another nucleotide, as illustrated in the figure on the right. The nitrogenous base sticks out from the chain. It is available to bond with bases in other nucleic acids. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. Two types of nucleic acids are found in living things. One is deoxyribonucleic (dee AHK sih rib oh noo klay ihk) acid, or DNA. The other is ribonucleic (rib oh noo KLAY ihk) acid, or RNA. Picture This DNA is the “genetic code.” DNA stores all the instructions 7. Circle each nucleotide for organisms to grow, reproduce, and adapt. The main grouping in the nucleic acid function of RNA is to use the information stored in DNA to on the right of the figure. make proteins. 0HOSPHATE / / ˆ. ˆ.( # # 3UGAR "ASE ˆ ˆ (/ ˆ 0 ˆ / ˆˆ #(. ˆ # # 0HOSPHATE / ( (/ ( 3UGAR "ASE 0HOSPHATE GROUP # ( ( # 0HOSPHATE ( #.ITROGEN CONTAINING # ( BASE 3UGAR "ASE /( /( 0HOSPHATE 3UGAR 3UGAR "ASE.UCLEOTIDE.UCLEIC ACID 68 Chapter 6 Chemistry in Biology Reading Essentials