2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

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

42. 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

43. 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

44. 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

45. 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

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

47. 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

48. 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

49. 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

50. 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

51. 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

52. 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

53. 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

54. 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

55. 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

56. 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

57. 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

58. 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

59. 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

60. 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

61. 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

62. 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

63. 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

64. 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

65. 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

66. 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

67. 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

68. 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

69. 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

70. 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

71. 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

72. 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

73. 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

74. 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

75. 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

76. 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

77. 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

78. 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

79. 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

80. 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

81. 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

82. 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

83. 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

84. 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

85. 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

86. 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

87. 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

88. 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

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

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

91. 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

92. 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

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

94. 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

95. 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

96. 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

97. 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

98. 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

99. 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

100. 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

101. 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

102. 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

103. 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

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

105. 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

106. 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

107. 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

108. 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

109. 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

110. 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

111. 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

112. 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

113. 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

114. Aaron Haupt Corbis Digital Stock Elaine Shay Mark Thayer PhotoDisc
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Aaron Haupt
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Elaine Shay
Mark Thayer
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Alton Biggs
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116. End of Chapter 6 Show