SECTION ATOMS, IONS, AND MOLECULES 2.1 Study Guide

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SECTION2.1ATOMS, IONS, AND MOLECULESStudy GuideKEY CONCEPTAll living things are based on atoms andtheir interactions.MAIN IDEA:VOCABULARYatomelementcompoundionionic bondcovalent bondmoleculeLiving things consist of atoms of different elements.1. How are atoms and elements related?Copyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of Life2. Sketch the structure of an atom. Label the protons, neutrons, nucleus, and electrons.3. How do compounds differ from elements?MAIN IDEA:Ions form when atoms gain or lose electrons.4. What is an ion?5. Why does an ion have an electrical charge?Unit 1 Resource BookMcDougal Littell BiologyStudy Guide31

STUDY GUIDE, CONTINUED6. In the spaces provided below, sketch how both positive and negative ions form. LabelCHAPTER 2Chemistry of Lifethe nucleus and the electrons. Use Figure 2.3 as a reference.MAIN IDEA:Atoms share pairs of electrons in covalent bonds.7. What is a covalent bond?Vocabulary Checkelementcompoundionmolecule9. atoms held together by covalent bonds10. composed of different types of atoms11. composed of one type of atom12. atom that has gained or lost electrons13. What is the difference between how ionic and covalent bonds form?32Study GuideUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.8. What determines the number of covalent bonds that an atom can form?

SECTIONATOMS, IONS, AND MOLECULES2.1Power NotesAtom:1.Energy levels:2.Composed of:Element:Outermost energy levels:3.CHAPTER 2Chemistry of Life4.Element:Compound:Ionic bonds:Copyright McDougal Littell/Houghton Mifflin Company.Ions:Positive ions:Covalent bonds:Unit 1 Resource BookMcDougal Littell BiologyNegative ions:Molecules:Power Notes33

SECTION2.1ATOMS, IONS, AND MOLECULESReinforcementKEY CONCEPT All living things are based on atoms and their interactions.Different types of atoms are called elements, which cannot be broken down by ordinarychemical means. Which element an atom is depends on the number of protons in theatom’s nucleus. For example, all hydrogen atoms have one proton, and all oxygen atomshave 16 protons. Only about 25 different elements are found in organisms. Atoms ofdifferent elements can link, or bond, together to form compounds. Atoms form bondsin two ways. Ionic bonds: An ion is an atom that has gained or lost one or more electrons. Someatoms form positive ions, which happens when an atom loses electrons. Otheratoms form negative ions, which happens when an atom gains electrons. An ionicbond forms through the electrical force between oppositely charged ions. Covalent bonds: A covalent bond forms when atoms share one or more pairs ofelectrons. A molecule is two or more atoms that are held together by covalentbonds.Copyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeAll matter, whether living or nonliving, is made of the same tiny building blocks, calledatoms. An atom is the smallest basic unit of matter. All atoms have the same basicstructure, composed of three smaller particles. Protons: A proton is a positively charged particle in an atom’s nucleus. Thenucleus is the dense center of an atom. Neutrons: A neutron has no electrical charge, has about the same mass as a proton,and is also found in an atom’s nucleus. Electrons: An electron is a negatively charged particle found outside the nucleus.Electrons are much smaller than either protons or neutrons.1. What are the parts of an atom?2. What makes atoms of one element different from the atoms of another element?3. How are ionic bonds and covalent bonds different?34ReinforcementUnit 1 Resource BookMcDougal Littell Biology

SECTION2.2PROPERTIES OF WATERStudy GuideKEY CONCEPTWater’s unique properties allow life toexist on Earth.MAIN IDEA:VOCABULARYhydrogen HLife depends on hydrogen bonds in water.1. What is a polar molecule?CHAPTER 2Chemistry of Life2. Explain why water is a polar molecule.3. What is a hydrogen bond?4. Describe where a hydrogen bond can form among water molecules.Copyright McDougal Littell/Houghton Mifflin Company.Complete the table by writing short descriptions about the properties of water.PropertyDescriptionHigh specific heat5.Cohesion6.Adhesion7.Unit 1 Resource BookMcDougal Littell BiologyStudy Guide35

STUDY GUIDE, CONTINUEDMAIN IDEA:Many compounds dissolve in water.8. What is the difference between a solvent and a solute?9. What types of substances dissolve easily in water?CHAPTER 2Chemistry of Life10. What types of substances do not dissolve easily in water?MAIN IDEA:Some compounds form acids or bases.11. Take notes about the characteristics of acids and bases in the table below.CharacteristicAcidBaseEffect on H concentration ina solutionEffect on pH12. In the space below, sketch a solution using the Visual Vocab on page 42 as a reference.Label the solution, solvent, and solute. Next to these labels, write brief definitionsfor the terms.36Study GuideUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.Vocabulary Check

SECTIONPROPERTIES OF WATER2.2Power NotesPolar molecules:Atom:Charge:1.Nonpolar molecules:2. Explain:CHAPTER 2Chemistry of LifeAtom:Charge:Properties of water related to hydrogen bonds:1.2.Copyright McDougal Littell/Houghton Mifflin :Bases:pH:pH:pH:Unit 1 Resource BookMcDougal Littell BiologyPower Notes37

SECTION2.2PROPERTIES OF WATERReinforcementThe structure of the water molecule gives water unique properties. Water is a polarmolecule, which means that it has a region with a slight negative charge (the oxygenatom), and a region with a slight positive charge (the hydrogen atoms). The oppositelycharged regions of water molecules interact to form hydrogen bonds. A hydrogen bondis an attraction between a slightly positive hydrogen atom and a slightly negative atom.Hydrogen bonds are responsible for several important properties of water. High specific heat: Water resists changes in temperature; it must absorb a largeamount of heat energy to increase in temperature. Cohesion: The attraction among molecules of a substance is called cohesion.Cohesion due to hydrogen bonds makes water molecules “stick” together. Adhesion: The attraction among molecules of different substances is calledadhesion. Water molecules “stick” to many other materials because of hydrogenbonds.Many compounds that are important for life dissolve in water. Water is the largestcomponent of cells’ interiors, and chemical reactions in the cell take place in thiswater. When one substance dissolves in another, a solution is formed. The substancepresent in the greatest amount is called the solvent. Substances that are present inlower amounts and dissolve in the solvent are called solutes. Polar solvents, such aswater, dissolve polar molecules and ions.When some substances dissolve in water they break up into ions. A compound thatreleases a hydrogen ion (a proton) when it dissolves in water is an acid. Bases arecompounds that remove, or accept, hydrogen ions. A solution’s acidity, or its hydrogenion concentration, is measured on the pH scale. An acid has a low pH (pH below 7)and a high hydrogen ion concentration. A base has a high pH (pH above 7) and a lowhydrogen ion concentration. Organisms must maintain a stable pH. Even a small changein pH can disrupt many biological processes.1. How do hydrogen bonds form?2. What are the two parts of a solution?3. What does pH measure?38ReinforcementUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeKEY CONCEPT Water’s unique properties allow life to exist on Earth.

SECTION2.3CARBON-BASED MOLECULESStudy GuideKEY CONCEPTCarbon-based molecules are thefoundation of life.MAIN y acidproteinamino acidnucleic acidCarbon atoms have unique bonding properties.1. Why is carbon often called the building block of life?CHAPTER 2Chemistry of Life2. What ability allows carbon atoms to form a large number of molecules?3. In the space below, sketch the three basic structures of carbon-based molecules: straightCopyright McDougal Littell/Houghton Mifflin Company.chain, branched chain, and ring.Unit 1 Resource BookMcDougal Littell BiologyStudy Guide39

STUDY GUIDE, CONTINUEDMAIN IDEA: Four main types of carbon-based molecules are found in living things.Complete the table with functions and examples of each type of carbon-based molecule.CHAPTER 2Chemistry of LifeMolecule ein8.9.10.11.Nucleic acid13. What are nucleic acids made of?Vocabulary Check14. The prefix mono- means “one,” and the prefix poly- means “many.” How are thesemeanings related to the terms monomer and polymer?40Study GuideUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.12. What determines a protein’s structure and function?

SECTIONCARBON-BASED MOLECULES2.3Power NotesMonomer:FunctionsExample1. CarbohydratePolymer – cellulose2.Monomer:Molecule:3.Polymer:CHAPTER 2Chemistry of LifeCopyright McDougal Littell/Houghton Mifflin Company.Type of MoleculePolymer:Monomer:Nucleic AcidsUnit 1 Resource BookMcDougal Littell BiologyTypes:Functions:Power Notes41

SECTION2.3CARBON-BASED MOLECULESReinforcementCarbon atoms are the basis of most molecules that make up living things. Manycarbon-based molecules are large molecules called polymers that are made ofmany smaller, repeating molecules called monomers. There are four main types ofcarbon-based molecules in living things. Carbohydrates include sugars and starches, and are often broken down as a sourceof chemical energy for cells. Some carbohydrates are part of cell structure, such ascellulose, which makes up plant cell walls. Lipids include fats and oils and, like carbohydrates, are often broken down asa source of chemical energy for cells. One type of lipid, called a phospholipid,makes up most of all cell membranes. Proteins have a large number of structures and functions. Some proteins areneeded for muscle movement; another protein, called hemoglobin, transportsoxygen in blood. Another type of proteins, called enzymes, speed up chemicalreactions in cells. Nucleic acids are molecules that store genetic information and build proteins.DNA stores genetic information in cells, and RNA helps to build the proteinsfor which DNA codes.Type of .Protein5.6.Nucleic acid7.8.ReinforcementCopyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeKEY CONCEPT Carbon-based molecules are the foundation of life.Unit 1 Resource BookMcDougal Littell Biology

SECTION2.4CHEMICAL REACTIONSStudy GuideKEY CONCEPTLife depends on chemical reactions.MAIN IDEA:VOCABULARYchemical reactionreactantproductbond energyequilibriumactivation energyexothermicendothermicBonds break and form during chemical reactions.1. Label the reactants and products in the chemical reaction shown below. Write briefdefinitions for these terms next to their labels.CHAPTER 2Chemistry of LifeCH4 2O2CO2 2H2O2. What causes chemical bonds to break during a reaction?Copyright McDougal Littell/Houghton Mifflin Company.3. What is bond energy?4. In a chemical equation, what symbol is used to show that a chemical reaction goesin both directions?5. When does a chemical reaction reach equilibrium?Unit 1 Resource BookMcDougal Littell BiologyStudy Guide43

STUDY GUIDE, CONTINUEDMAIN IDEA:Chemical reactions release or absorb energy.6. Theof the reactants and products determines whetherenergy will be released or absorbed during a chemical reaction.7. Before a chemical reaction can start,must be absorbedby the reactants. The amount that must be absorbed to start the reaction is called the.8. In an exothermic reaction, the products have aCHAPTER 2Chemistry of Lifeenergy than the reactants. Overall, energy isbond.9. In an endothermic reaction, the products have aenergy than the reactants. Overall, energy isbond.Vocabulary Check10. Write one sentence that uses the words chemical reaction, reactant, and product.12. The term equilibrium is based on two Latin roots that mean “equal” and “balance.” Howdo these meanings tell you the meaning of equilibrium in a chemical reaction?13. The prefix exo- means “out,” and the prefix endo- means “in.” What do these prefixestell you about exothermic and endothermic reactions?44Study GuideUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.11. Write your own analogy to remember the meaning of activation energy.

SECTIONCHEMICAL REACTIONS2.4Power NotesChemical Reaction6O2 C6H12O66CO2 6H2O2.1.3.Chemical equilibrium:Exothermic:CHAPTER 2Chemistry of LifeBond energy:5.EnergyReaction progress7.4.Endothermic:9.10.EnergyCopyright McDougal Littell/Houghton Mifflin Company.6.Reaction progress8.Unit 1 Resource BookMcDougal Littell Biology11.Power Notes45

SECTION2.4CHEMICAL REACTIONSReinforcementKEY CONCEPT Life depends on chemical reactions.At the most fundamental level, every process that takes place in an organism dependson chemical reactions. In a chemical reaction, substances are changed into differentsubstances by the breaking and forming of chemical bonds. The substances that arepresent at the start of a chemical reaction, and are changed by the reaction, are calledreactants. The substances that are formed by a chemical reaction are the products.All chemical reactions require the input of at least a small amount of energy in orderfor bonds to break in the reactants and for the reaction to start. The energy needed tostart a chemical reaction is the activation energy. In general, there are two types ofenergy changes that can occur during a chemical reaction. Exothermic reaction: An exothermic chemical reaction releases more energy thanit absorbs. The bonds that are broken in the reactants of an exothermic reactionhave a higher bond energy than the new bonds that form in the products. Energy isusually released as heat or light. Endothermic reaction: An endothermic chemical reaction absorbs more energythan it releases. The bonds that are broken in the reactants of an endothermicreaction have a lower bond energy than the new bonds that form in the products.The energy that is absorbed makes up for the difference.Copyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeChemical bonds must be broken in the reactants and new ones must be formed in theproducts. Energy must be added to break chemical bonds. In contrast, energy is alwaysreleased when new bonds form. The amount of energy needed to break a bond, or theamount of energy released when a bond forms, is called bond energy.1. What are the two parts of a chemical reaction?2. What is activation energy?3. How are exothermic reactions different from endothermic reactions?46ReinforcementUnit 1 Resource BookMcDougal Littell Biology

SECTION2.5ENZYMESStudy GuideKEY CONCEPTEnzymes are catalysts for chemical reactions in livingthings.MAIN IDEA:VOCABULARYcatalystenzymesubstrateA catalyst lowers activation energy.1. What is activation energy?CHAPTER 2Chemistry of Life2. Take notes about catalysts in the chart below. In the first two boxes, write detail notesabout the main functions of catalysts. In the third box, write a detail about anothercharacteristic.Copyright McDougal Littell/Houghton Mifflin Company.A catalyst lowers activation energy.3. When a catalyst is present, more / less activation energy is needed to start a chemicalreaction.Unit 1 Resource BookMcDougal Littell BiologyStudy Guide47

STUDY GUIDE, CONTINUEDMAIN IDEA:conditions.Enzymes allow chemical reactions to occur under tightly controlled4. Take notes about enzymes by filling in the Main Idea Web below.How structureaffects function:EnzymesImportant factorsin enzyme structure:Lock-and-key model:5. How do enzymes weaken the bonds in substrates?Vocabulary Check6. The word catalyst comes from the Greek word meaning “to dissolve.” How does thisdefinition relate to the meaning of catalyst?7. How are substrates like keys and enzymes like locks?48Study GuideUnit 1 Resource BookMcDougal Littell BiologyCopyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeWhy enzymesare necessary:

SECTIONENZYMES2.5Power NotesA Catalyst:1.2.Enzymes:Homeostasis and enzymes:CHAPTER 2Chemistry of LifeCopyright McDougal Littell/Houghton Mifflin Company.Enzyme structure and function:Substrates and Lock-and-Key Model of Enzyme FunctionSubstrates:Unit 1 Resource BookMcDougal Littell BiologyLock-and-key model:Power Notes49

SECTION2.5ENZYMESReinforcementKEY CONCEPT Enzymes are catalysts for chemical reactions in living things.In living things, enzymes are catalysts for chemical reactions. Almost all enzymesare proteins, and almost every process in living things needs enzymes. The functionof each enzyme depends on its structure. A change in biological conditions within anorganism can affect the shape of an enzyme, which can decrease or prevent an enzymefrom working properly. For example, enzymes function best in a small range around anorganism’s normal temperature and pH.The shape of an enzyme is important because it allows only certain molecules to bind tothe enzyme. The specific molecules that an enzyme acts on are called substrates. Oneway to think of enzyme function is called the lock-and-key model. Substrates bind to anenzyme like the way in which a key fits into a lock. If an enzyme’s structure changes,the substrates cannot bind to the enzyme. Substrates bind to an enzyme. The enzyme brings molecules close together so thatthey can react with one another. The bonds inside the substrates are stretched slightly out of position, which weakensthe bonds. Less energy is needed to break weaker bonds. The reaction takes place and the product is released from the enzyme. The enzymecan then bind to more of the substrate molecules.Copyright McDougal Littell/Houghton Mifflin Company.CHAPTER 2Chemistry of LifeChemical reactions require the addition of energy, called activation energy, to take place.Even if a chemical reaction starts, it may not happen very quickly. However, both theactivation energy and the rate of a chemical reaction can be changed by a chemicalcatalyst. A catalyst is a substance that decreases the activation energy for a reaction andincreases the rate of the reaction.1. What is a catalyst?2. Where are enzymes found?3. How does an enzyme work?50ReinforcementUnit 1 Resource BookMcDougal Littell Biology

CHAPTER2INDEPENDENT AND DEPENDENT VARIABLESData Analysis PracticeDuring experiments scientists manipulate or change an independent variable to observe ormeasure its effects on a dependent variable.Chemists working for a pharmaceutical company carry out an experiment in which theymeasure the amount of time it takes for different amounts of an antacid to neutralize 1 mL ofhydrochloric acid (HCl). The results of their experiment are shown in the graph below.GRAPH 1: ANTACID AMOUNTS ANDNEUTRALIZATION TIMES25CHAPTER 2Chemistry of LifeTime (min)2015105Copyright McDougal Littell/Houghton Mifflin Company.0750 1000 1250 1500 1750 2000 2250 2500 2750 3000Amount of antacid (mg)1. Identify What are the independent and dependent variables in this experiment?2. Analyze What is the relationship between the amount of antacid and the length oftime to neutralize the acid?Unit 1 Resource BookMcDougal Littell BiologyData Analysis Practice51

CHAPTER2SURFACE TENSION AND COHESIONPre-AP ActivityIn Chapter 2, you have learned that water is a highly polar molecule that forms hydrogenbonds with other water molecules. Many of the physical properties of water—such as surfacetension, capillarity, adhesion, and cohesion—result from hydrogen bonding.INTERMOLECULAR FORCES CAUSE SURFA

CARBON-BASED MOLECULES Reinforcement KEY CONCEPT Carbon-based molecules are the foundation of life. Carbon atoms are the basis of most molecules that make up living things. Many carbon-based molecules are large molecules called polymers that are made of many smaller, repeating molecules called monomers. There are four main types of

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