Table of Contents – pages iv-v Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: Invertebrates Unit 9: Vertebrates Unit 10: The Human Body Table of Contents – pages iv-v

Table of Contents – pages iv-v Unit 1: What is Biology? Chapter 1: Biology: The Study of Life Unit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and Conservation Unit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell Table of Contents – pages iv-v

Table of Contents – pages iv-v Unit 4: Genetics Chapter 10: Mendel and Meiosis Chapter 11: DNA and Genes Chapter 12: Patterns of Heredity and Human Genetics Chapter 13: Genetic Technology Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity Table of Contents – pages iv-v

Table of Contents – pages iv-v Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18: Viruses and Bacteria Chapter 19: Protists Chapter 20: Fungi Unit 7: Plants Chapter 21: What Is a Plant? Chapter 22: The Diversity of Plants Chapter 23: Plant Structure and Function Chapter 24: Reproduction in Plants Table of Contents – pages iv-v

Table of Contents – pages iv-v Unit 8: Invertebrates Chapter 25: What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates Table of Contents – pages iv-v

Table of Contents – pages iv-v Unit 9: Vertebrates Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds Chapter 32: Mammals Chapter 33: Animal Behavior Unit 10: The Human Body Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development Chapter 39: Immunity from Disease Table of Contents – pages iv-v

The Life of a Cell The Chemistry of Life A View of the Cell Cellular Transport and the Cell Cycle Energy in a Cell Unit Overview – pages 138-139

Chapter Contents – page viii Chapter 6 The Chemistry of Life 6.1: Atoms and Their Interactions 6.1: Section Check 6.2: Water and Diffusion 6.2: Section Check 6.3: Life Substances 6.3: Section Check Chapter 6 Summary Chapter 6 Assessment Chapter Contents – page viii

You will explain why water is important in life. What You’ll Learn You will relate an atom’s interactions with other atoms to its structure. You will explain why water is important in life. You will compare the role of biomolecules in organisms. Chapter Intro-page 140

6.1 Section Objectives – page 141 Relate the structure of an atom to the identity of elements. Relate the formation of covalent and ionic chemical bonds to the stability of atoms. 6.1 Section Objectives – page 141

6.1 Section Objectives – page 141 Distinguish mixtures and solutions. Define acids and bases and relate their importance to biological systems. 6.1 Section Objectives – page 141

Section 6.1 Summary – pages 141-151 Elements Everything – whether it is a rock, frog, or flower – is made of substances called elements. An element is a substance that can’t be broken down into simpler chemical substances. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Natural elements in living things Of the naturally occurring elements on Earth, only about 25 are essential to living organisms. Carbon, hydrogen, oxygen, and nitrogen make up more that 96 percent of the mass of a human body. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Trace elements Trace elements such as iron and copper, play a vital role in maintaining healthy cells in all organisms. Plants obtain trace elements by absorbing them through their roots; animals get them from the foods they eat. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Table 6.1 Some Elements That Make Up the Human Body Percent By Mass in Human Body Percent By Mass in Human Body Element Symbol Element Symbol Oxygen O 65.0 Iron Fe trace Carbon C 18.5 Zinc Zn trace Hydrogen H 9.5 Copper Cu trace Nitrogen N 3.3 Iodine I trace Calcium Ca 1.5 Manganese Mn trace Phosphorus P 1.0 Boron B trace Potassium K 0.4 Chromium Cr trace Sulfur S 0.3 Molybdenum Mo trace Sodium Na 0.2 Cobalt Co trace Chlorine Cl 0.2 Selenium Se trace Magnesium Mg 0.1 Fluorine F trace Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Atoms: The Building Blocks of Elements An atom is the smallest particle of an element that has the characteristics of that element. Atoms are the basic building blocks of all matter. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 The structure of an atom The center of an atom is called the nucleus (NEW klee us). All nuclei contain positively charged particles called protons (p+). Most contain particles that have no charge, called neutrons (n0). Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 The Structure of an atom The region of space surrounding the nucleus contains extremely small, negatively charged particles called electrons (e-) This region of space is referred to as an electron cloud. Nucleus Electron energy levels Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 The Structure of an atom Because opposites attract, the negatively charged electrons are held in the electron cloud by the positively charged nucleus. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Nucleus Electron energy levels 8 protons (p+) 8 neutrons (n0) Electrons exist around the nucleus in regions known as energy levels. Oxygen atom The first energy level can hold only two electrons. The second level can hold a maximum of eight electrons. The third level can hold up to 18 electrons. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Electron energy levels Atoms contain equal numbers of electrons and protons; therefore, they have no net charge. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Isotopes of an Element Atoms of the same element always have the same number of protons but may contain different numbers of neutrons. Atoms of the same element that have different numbers of neutrons are called isotopes (I suh tophs) of that element. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Compounds and Bonding A compound is a substance that is composed of atoms of two or more different elements that are chemically combined. Table salt (NaCl) is a compound composed of the elements sodium and chlorine. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How covalent bonds form Atoms combine with other atoms only when the resulting compound is more stable than the individual atoms. For many elements, an atom becomes stable when its outermost energy level is full. Sharing electrons with other atoms is one way for elements to become stable. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How covalent bonds form Two hydrogen atoms can combine with each other by sharing their electrons. Hydrogen molecule Each atom becomes stable by sharing its electron with the other atom. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How covalent bonds form Click image to view movie. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How covalent bonds form The attraction of the positively charged nuclei for the shared, negatively charged electrons holds the atoms together. Hydrogen molecule Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How covalent bonds form A covalent bond holds the two hydrogen atoms together. A molecule is a group of atoms held together by covalent bonds. It has no overall charge. Water molecule Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 How ionic bonds form An atom (or group of atoms) that gains or loses electrons has an electrical charge and is called an ion. An ion is a charged particle made of atoms. The attractive force between two ions of opposite charge is known as an ionic bond. Click image to view movie. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Chemical Reactions Chemical reactions occur when bonds are formed or broken, causing substances to recombine into different substances. Ionic bond + Na+ ion: 11p+ Na atom: 11p+ Cl atom: 17p+ Cl― ion: 17p+ 10e ― 11e ― 17e ― 18e ― Sodium atom + Chlorine atom Sodium+ Ion + Chlorine― ion Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Chemical Reactions All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism. Ionic bond + Na+ ion: 11p+ Na atom: 11p+ Cl atom: 17p+ Cl― ion: 17p+ 10e ― 11e ― 17e ― 18e ― Sodium atom + Chlorine atom Sodium+ Ion + Chlorine― ion Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Writing chemical equations In a chemical reaction, substances that undergo chemical reactions, are called reactants. Substances formed by chemical reactions, are called products. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Writing chemical equations A molecule of table sugar can be represented by the formula: C12H22O11. The easiest way to understand chemical equations is to know that atoms are neither created nor destroyed in chemical reactions. They are simply rearranged. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Mixtures and Solutions A mixture is a combination of substances in which the individual components retain their own properties. Neither component of the mixture changes. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Mixtures and Solutions A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent). Sugar molecules in a powdered drink mix dissolve easily in water to form a solution. Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Acids and bases Chemical reactions can occur only when conditions are right. A reaction may depend on: - energy availability - temperature - concentration of a substance - pH of the surrounding environment Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Acids and bases The pH is a measure of how acidic or basic a solution is. A scale with values ranging from below 0 to above 14 is used to measure pH. More acidic Neutral More basic Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Acids and bases Substances with a pH below 7 are acidic. An acid is any substance that forms hydrogen ions (H+) in water. A solution is neutral if its pH equals zero. More acidic Neutral More basic Section 6.1 Summary – pages 141-151

Section 6.1 Summary – pages 141-151 Acids and bases Substances with a pH above 7 are basic. A base is any substance that forms hydroxide ions (OH-) in water. pH 11 Section 6.1 Summary – pages 141-151

Question 1 Which of the following is an element? A. chlorophyll B. carbon C. sodium chloride D. water NC: 2.01 Section 1 Check

The answer is B. An element can't be broken down into simpler chemical substances. Chemical elements combine in different ways to form a variety of substances useful to living things. NC: 2.01 Section 1 Check

NC: 2.01 Table 6.1 Some Elements That Make Up the Human Body Percent By Mass in Human Body Percent By Mass in Human Body Element Symbol Element Symbol Oxygen O 65.0 Iron Fe trace Carbon C 18.5 Zinc Zn trace Hydrogen H 9.5 Copper Cu trace Nitrogen N 3.3 Iodine I trace Calcium Ca 1.5 Manganese Mn trace Phosphorus P 1.0 Boron B trace Potassium K 0.4 Chromium Cr trace Sulfur S 0.3 Molybdenum Mo trace Sodium Na 0.2 Cobalt Co trace Chlorine Cl 0.2 Selenium Se trace Magnesium Mg 0.1 Fluorine F trace NC: 2.01 Section 1 Check

Question 2 The smallest particle of an element that has the characteristics of that element is a(n) __________. A. proton C. nucleus B. electron D. atom Section 1 Check

The answer is D. Atoms are the basic building blocks of all matter and have the same general structure, including a nucleus and electrons. Elements found in both living and nonliving things are made of atoms. Nucleus An atom has a nucleus and electrons in energy levels. Electron energy levels Section 1 Check

Question 3 Which of the following can contain two types of particles? A. nucleus B. protons C. neutrons D. electrons Section 1 Check

The answer is A. The nucleus is the center of the atom and may contain both positively charged particles and particles that have no charge. Nucleus 8 protons (p+) 8 neutrons (n0) Oxygen atom Section 1 Check

Question 4 Sodium and chlorine combine to form table salt. What do you know to be true? A. Sodium and chlorine are sharing electrons in their outer energy levels. B. Sodium and chlorine atoms have no overall electrical charge. Section 1 Check

Question 4 Sodium and chlorine combine to form table salt. What do you know to be true? C. Sodium and chlorine are less stable in the compound sodium chloride. D. Sodium and chlorine atoms in table salt have full outer energy levels. Section 1 Check

The answer is D. Sodium and chlorine atoms combine because the resulting compound, table salt, is more stable than the individual atoms. Sodium loses an electron in its outer energy level, chlorine gains that electron in its outer energy level, and an ionic bond is formed. Section 1 Check

Section 2 Objectives – page 152 Relate water’s unique features to polarity. Identify how the process of diffusion occurs and why it is important to cells. Section 2 Objectives – page 152

Summary Section 2 – pages 152-156 Water and Its Importance Water is perhaps the most important compound in living organisms. Water makes up 70 to 95 percent of most organisms. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Water is Polar Sometimes, when atoms form covalent bonds they do not share the electrons equally. This is called a polar bond. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Water is Polar A polar molecule is a molecule with an unequal distribution of charge; that is, each molecule has a positive end and a negative end. Water is an example of a polar molecule. Water can dissolve many ionic compounds, such as salt, and many other polar molecules, such as sugar. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Water is Polar Water molecules also attract other water molecules. Hydrogen atom Weak hydrogen bonds are formed between positively charged hydrogen atoms and negatively charged oxygen atoms. Hydrogen atom Oxygen atom Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Water resists temperature changes Water resists changes in temperature. Therefore, water requires more heat to increase its temperature than do most other common liquids. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Water expands when it freezes Water is one of the few substances that expands when it freezes. Ice is less dense than liquid water so it floats as it forms in a body of water. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Early observations: Bownian motion In 1827, Scottish scientist Robert Brown used a microscope to observe pollen grains suspended in water. He noticed that the grains moved constantly in little jerks, as if being struck by invisible objects. This motion is now called Brownian motion. Today we know that Brown was observing evidence of the random motion of atoms and molecules. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 The process of diffusion Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. Diffusion results because of the random movement of particles (Brownian motion). Three key factors—concentration, temperature, and pressure—affect the rate of diffusion. Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 The results of diffusion When a cell is in dynamic equilibrium with its environment, materials move into and out of the cell at equal rates. As a result, there is no net change in concentration inside or outside the cell. Material moving out of cell equals material moving into cell Summary Section 2 – pages 152-156

Summary Section 2 – pages 152-156 Diffusion in living systems The difference in concentration of a substance across space is called a concentration gradient. Ions and molecules diffuse from an area of higher concentration to an area of lower concentration, moving with the gradient. Dynamic equilibrium occurs when there is no longer a concentration gradient. Summary Section 2 – pages 152-156

Question 1 Answer Explain why water is important to living organisms. Living organisms must have water for life processes, because critical molecules and ions must be free to move and collide, which only happens when they are dissolved in water. Water also transports materials in living organisms, such as in blood or sap. Section 2 Check

Question 2 Positively charged end + How does water's chemical structure impact its role in living organisms? + ― Negatively charged end NC: 2.03 Section 2 Check

Because water is polar, it can dissolve many ionic compounds and polar molecules. Water has the property of capillary action that enables plants to get water from the ground. Water also resists temperature changes, which allows cells to maintain homeostasis. NC: 2.03 Section 2 Check

Question 3 Which of the following best describes diffusion? A. slow process resulting from random movement of particles B. net movement of particles from area of low concentration to area of high concentration NC: 2.03 Section 2 Check

Question 3 Which of the following best describes diffusion? C. rapid process that is unaffected by increases in temperature D. net movement of particles from high to low concentrations that accelerates when pressure decreases NC: 2.03 Section 2 Check

The answer is A. Diffusion is a slow process resulting from the random movement of particles, and is the net movement of particles from areas of high concentration to areas of lower concentration. NC: 2.03 Section 2 Check

6.3 Section Objectives – page 157 Classify the variety of organic compounds. Describe how polymers are formed and broken down in organisms. Compare the chemical structures of carbohydrates, lipids, proteins, and nucleic acids, and relate their importance to living things. Identify the effects of enzymes. 6.3 Section Objectives – page 157

6.3 Section Summary 6.3 – pages 157-163 The Role of Carbon in Organisms A carbon atom has four electrons available for bonding in its outer energy level. In order to become stable, a carbon atom forms four covalent bonds that fill its outer energy level. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The Role of Carbon in Organisms Two carbon atoms can form various types of covalent bonds—single, double or triple. Single Bond Double Bond Triple Bond 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 Molecular chains Carbon compounds vary greatly in size. When carbon atoms bond to each other, they can form straight chains, branched chains, or rings. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 Molecular chains Small molecules bond together to form chains called polymers. A polymer is a large molecule formed when many smaller molecules bond together. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of carbohydrates A carbohydrate is a biomolecule composed of carbon, hydrogen, and oxygen with a ratio of about two hydrogen atoms and one oxygen atom for every carbon atom. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of carbohydrates The simplest type of carbohydrate is a simple sugar called a monosaccharide (mah noh SA kuh ride). (ie. glucose, fructose) The largest carbohydrate molecules are polysaccharides, polymers composed of many monosaccharide subunits. (ie. potatoes, liver) 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of lipids Lipids are large biomolecules that are made mostly of carbon and hydrogen with a small amount of oxygen. (ie. fats, oils, waxes) They are insoluble in water because their molecules are nonpolar and are not attracted by water molecules. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of proteins A protein is a large, complex polymer composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of proteins The basic building blocks of proteins are called amino acids. There are about 20 common amino acids that can make literally thousands of proteins. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of proteins Peptide bonds are covalent bonds formed between amino acids. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of proteins Proteins are the building blocks of many structural components of organisms. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of proteins Enzymes are important proteins found in living things. An enzyme is a protein that changes the rate of a chemical reaction. They speed the reactions in digestion of food. Click image to view movie. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of nucleic acids A nucleic (noo KLAY ihk) acid is a complex biomolecule that stores cellular information in the form of a code. Nucleic acids are polymers made of smaller subunits called nucleotides. 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of nucleic acids Nucleotides are arranged in three groups—a nitrogenous base, a simple sugar, and a phosphate group. Phosphate Sugar Nitrogenous base 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of nucleic acids DNA, which stands for deoxyribonucleic acid is a nucleic acid. Phosphate Sugar Nitrogenous base 6.3 Section Summary 6.3 – pages 157-163

6.3 Section Summary 6.3 – pages 157-163 The structure of nucleic acids The information coded in DNA contains the instructions used to form all of an organism’s enzymes and structural proteins. Another important nucleic acid is RNA, which stands for ribonucleic acid. RNA is a nucleic acid that forms a copy of DNA for use in making proteins. 6.3 Section Summary 6.3 – pages 157-163

Question 1 How many covalent bonds does a carbon atom need to form in order to become stable? A. 1 B. 2 C. 3 D. 4 Section 3 Check

The answer is D. A carbon atom has four electrons available for bonding in its outer energy level and needs to form four covalent bonds in order to become stable. Section 3 Check

Question 2 A __________ is a biomolecule composed of carbon, hydrogen, and oxygen with a ratio of about two hydrogen atoms and one oxygen atom for every carbon atom. A. carbohydrate C. protein B. lipid D. fatty acid NC: 2.01 Section 3 Check

The answer is A. Lipids are made mostly of carbon and hydrogen, and proteins contain nitrogen in addition to carbon, hydrogen and oxygen. NC: 2.01 Section 3 Check

Question 3 In which type of molecule will you find peptide bonds? A. carbohydrate C. protein B. lipid D. fatty acid Section 3 Check

The answer is C. Amino acids are the basic building blocks of proteins and are linked together by peptide bonds. Section 3 Check

What biomolecule is represented in this diagram? Question 4 What biomolecule is represented in this diagram? Phosphate Sugar Nitrogenous base A. carbohydrate C. protein B. nucleotide D. lipid Section 3 Check

The answer is B. Nucleotides are the smaller subunits that make up nucleic acids. Nucleotides are composed of three groups: a nitrogenous base, a simple sugar, and a phosphate group. Phosphate Sugar Nitrogenous base Section 3 Check

Question 5 Describe an enzyme and its function. NC: 2.04 Section 3 Check

An enzyme is a protein that enables other molecules to undergo chemical changes to form new products. Enzymes increase the speed of reactions that would otherwise proceed too slowly. Substrate Active site NC: 2.04 Section 3 Check

Atoms and Their Interactions Atoms are the basic building block of all matter. Atoms consist of a nucleus containing protons and usually neutrons. The positively charged nucleus is surrounded by rapidly moving, negatively charged electrons. Atoms become stable by bonding to other atoms through covalent or ionic bonds. Chapter Summary – 6.1

Atoms and Their Interactions Components of mixtures retain their properties. Solutions are mixtures in which the components are evenly distributed. Acids are substances that from hydrogen ions in water. Bases are substances that form hydroxide ions in water. Chapter Summary – 6.1

Water and Diffusion Water is the most abundant compound in living things. Water is an excellent solvent due to the polar property of its molecules. Particles of matter are in constant motion. Diffusion occurs from areas of higher concentration to areas of lower concentration. Chapter Summary – 6.2

Life Substances All organic compounds contain carbon atoms. There are four principal types of organic compounds, or biomolecules, that make up living things: carbohydrates, lipids, proteins, and nucleic acid. The structure of a biomolecule will help determine its properties and functions. Chapter Summary – 6.3

Question 1 What is the difference between a compound and an element? Answer A compound is a substance that is composed of atoms of two or more different elements that are chemically combined. An element is a substance that can't be broken down into simpler chemical substances. Chapter Assessment

Question 2 What is it called when atoms share electrons? Water molecule A. covalent bonding C. hydrogen bonding B. ionic bonding D. diffusion Chapter Assessment

The answer is A. Covalent bonds differ from ionic bonds in that the shared electrons move about the nuclei of both atoms of the covalent compound. Water molecule Chapter Assessment

Question 3 Which of the following combinations will produce a solution? A. chocolate chips and cookie dough B. sand and sugar crystals C. powdered drink mix and water D. oil and vinegar Chapter Assessment

The answer is C. All of the combinations are mixtures because the individual components retain their own properties. A solution is a mixture in which one or more substances is dissolved in another and will not settle out of solution. Water molecules Sugar molecules Sugar crystal Chapter Assessment

Question 4 What type of substance forms hydrogen ions in water? A. enzyme B. acid C. base D. polar Chapter Assessment

The answer is B. Any substance that forms hydrogen ions (H+) in water is an acid. The pH of a substance is a measure of how acidic or basic a solution is. Chapter Assessment

Question 5 Which of the following best describes a molecule with an unequal distribution of charge? A. polar B. acidic C. basic D. diffuse NC: 2.02 Chapter Assessment

The answer is A. Each polar molecule has a positive end and a negative end. Polar water molecules attract ions and other polar molecules, and can dissolve many ionic compounds. NC: 2.02 Chapter Assessment

Question 6 Name the chemical reaction illustrated in the diagram. A. hydrolysis CH2OH CH2OH O O Glucose OH OH HO B. condensation OH HO OH OH + O + H2O HOCH2 O OH HOCH2 O C. Protein synthesis Fructose HO HO CH2OH CH2OH OH OH D. glycolysis Sucrose NC: 2.03 Chapter Assessment

The answer is B. In condensation reactions, small molecules bond together to produce a polymer and water. CH2OH CH2OH O O Glucose OH OH HO OH HO OH OH + O + H2O HOCH2 O OH HOCH2 O Fructose HO HO CH2OH CH2OH OH OH Sucrose NC: 2.03 Chapter Assessment

Question 7 An oxygen atom has 8 protons and 8 neutrons. How many electrons does it have? A. 8 B. 18 C. 32 D. 0 Chapter Assessment

The answer is A. Atoms contain equal numbers of electrons and protons and have no net charge. Nucleus 8 protons (p+) 8 neutrons (n0) Oxygen atom Chapter Assessment

Question 8 Based on your knowledge of biomolecules, which of the following substances would be most effective at breaking down this polymer? CH2OH A. nuclease O B. lipase OH HO OH C. pepsin O D. water O HOCH2 HO CH2OH OH NC: 2.01 Chapter Assessment

The answer is D. This is a sucrose molecule, formed from glucose and fructose in a condensation reaction. The products of this reaction are the sucrose molecule and water. If water is added to sucrose, hydrolysis occurs and breaks the covalent bonds between the subunits. NC: 2.01 Chapter Assessment

Aaron Haupt Corbis Digital Stock Elaine Shay Mark Thayer PhotoDisc Photo Credits Aaron Haupt Corbis  Digital Stock Elaine Shay Mark Thayer PhotoDisc Alton Biggs Photo Credits

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