CHAPTER 2 ATOMS, MOLECULES, AND LIFE

AT A GLANCE

Case Study: Improving on Nature?

2.1 What Are Atoms?â Web Animation: Interactive AtomsA. Atoms Are Composed of Even Smaller Particles

1. Atom—basic structural unit of matter (Figure 2-1)a. Atomic nucleus—positively charged protons and neutronsb. Negatively charged electrons—orbit atomic nucleus

2. Elements—atoms with same number of protons (atomic number)a. Isotopes—same element; different number of neutronsb. Radioactive isotopes—release energy

B. Electrons Orbit the Nucleus, Forming Electron Shells (Figure 2-2)1. Innermost shell—lowest energy2. First shell holds 2 electrons3. Subsequent shells hold up to 8 electrons

2.2 How Do Atoms Form Molecules?A. Atoms Interact When There Are Vacancies in Their Outermost Electron Shells

1. Chemical bonds—hold atoms together; gain, loss, sharing of electrons2. Chemical reactions—making and breaking of chemical bonds3. A molecule may be depicted in different ways (Figure 2-4)

B. Charged Atoms Interact to Form Ionic Bonds (Figure 2-5)1. Outermost electron shell is almost empty or almost full2. Ions—atoms become stable by gaining or losing electrons3. Ionic bonds—electrical attraction between positive and negative ions

C. Uncharged Atoms Share Electrons to Form Covalent Bonds (Table 2.1)1. Most biological molecules use covalent bonding2. Covalent bonds are either nonpolar or polar

a. Nonpolar covalent bonds—equal sharing of electronsb. Polar covalent bonds—unequal sharing of electrons (H2O)

D. Hydrogen Bonds Form Between Molecules with Polar Covalent Bonds (Figure 2-7)1. Hydrogen bonds—bonds between parts of polar molecules2. Responsible for unique properties of water

â Lecture Activity 2.1: Exercise in Chemical Bondingâ Lecture Activity 2.2: Atomic Love Connection

2.3 Why Is Water So Important to Life?A. Water Interacts with Many Other Molecules

1. Water is involved in most chemical reactions in a cell2. Water plays a role in photosynthesis and digestion

B. Many Molecules Dissolve Easily in Water (Figure 2-8)â Web Animation: Water and Lifeâ Health Watch: Health Food?

1. A good solvent because it is a polar molecule2. Hydrophilic molecules—dissolve easily in water (ex. sugars)

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14 Instructor Guide

3. Hydrophobic molecules—do not dissolve in water (ex. fats and oils)

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C. Water Molecules Tend to Stick Together (Figure 2-9)1. Cohesion—water molecules stick together2. Surface tension—surface of water is resistant to being broken3. Adhesion—water sticks to polar surfaces

D. Water Can Form Ions (Figure 2-10)1. Water is ionized to form hydrogen ions (H+) and hydroxide ions (OH–)2. Acidic solutions—more hydrogen ions (H+) than hydroxide ions (OH–)3. Basic solutions—more hydroxide ions (OH–) than hydrogen ions (H+)4. pH measures acidity

a. Acids have a pH below 7 (more H+ than OH–)b. Bases have a pH above 7 (more OH– than H+)c. Water has a pH of 7 (equal amount of H+ and OH–)

5. A buffer maintains a solution at a constant pH

2.4 Why Is Carbon So Important to Life?A. Organic Molecules vs. Inorganic Molecules

1. Organic molecules contain carbon and hydrogen2. Inorganic molecules do not contain carbon3. Functional groups—attached to carbon backbones; determine characteristics of different molecules

2.5 How Are Biological Molecules Joined Together or Broken Apart?â Web Animation: Structure of Biological MoleculesA. Construction of Large Molecules Yields Water

1. Dehydration synthesisa. Individual subunits—linked together to make larger moleculesb. Water is formed during reaction

B. Breakdown of Large Molecules Uses Water (Table 2.3)1. Hydrolysis

a. Splitting larger molecules into individual subunitsb. Water is needed to complete reaction

2.6 What Are Carbohydrates?A. A Variety of Simple Sugars Occurs in Organisms (Figure 2-13)

1. Monosaccharides—one sugar moleculea. Glucose—subunit of most polysaccharidesb. Fructose—found in corn syrup

B. Disaccharides Store Energy (Figure 2-14)1. Disaccharides—two simple sugar molecules linked together

a. Sucrose—table sugar (glucose + fructose)b. Lactose—milk sugar (glucose + galactose)

2. Cells—can break apart disaccharides to get energyImproving on Nature? ContinuedC. Polysaccharides Store Energy and Provide Support

1. Polysaccharides—polymers of many monosaccharidesa. Starch—energy storage in plantsb. Glycogen—energy storage in animalsc. Cellulose—structural support in plants (Figure 2-15)d. Chitin—exoskeletons of insects, crabs, spiders

â Lecture Activity 2.3: Carbohydrate Reverse Questions

2.7 What Are Lipids?A. Oils, Fats, and Waxes Contain Only Carbon, Hydrogen, and Oxygen (Figure 2-16)

1. Fats and oilsa. Formed by dehydration synthesisb. Contain three fatty acids and a glycerol moleculec. Used for long-term storage in plants and animalsd. Store same energy with less weight than carbohydrates

2. Saturated vs. unsaturated fatsa. Saturated fats—no double bonds; solid at room temperatureb. Unsaturated fats—contain double bonds; liquid at room temperature

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Improving on Nature? Continuedâ Lecture Activity 2.4: Fake Fats: To Eat or Not to Eat?â Health Watch: Cholesterol—Friend and FoeB. Phospholipids Have Water-Soluble Heads and Water-Insoluble Tails (Figure 2-20)

1. Phospholipids contain 2 fatty acids, 1 glycerol, and 1 phosphate group2. Fatty acid “tails” are hydrophobic (water insoluble)3. Phosphate group “head” is polar and hydrophilic (water soluble)4. Central component of cell membranes

C. Steroids Consist of Four Carbon Rings Fused Together (Figure 2-21)1. Cholesterol is a steroid molecule

a. Important component of animal cell membranesb. Used to synthesize other steroids

2.8 What Are Proteins?A. Proteins Are Formed from Chains of Amino Acids (Figure 2-22)

1. Amino acids contain central carbon + four functional groupsa. Nitrogen-containing amino group (—NH2)b. Carboxyl group (—COOH)c. Hydrogen (—H)d. Variable group—gives each amino acid its distinctive properties

2. Sequence of amino acids dictates function of proteinB. Amino Acids Join by Dehydration Synthesis to Form Chains (Figure 2-24)

1. Peptide bond—amino group of one amino acid is joined to carboxyl group of another amino acid2. Polypeptide chain or protein—long chain of amino acids

C. Three-Dimensional Shapes Give Proteins Their Functions (Figure 2-25)1. Primary structure

a. Sequence of amino acids that make up the proteinb. Different proteins have different sequences of amino acids

2. Secondary structurea. Due to interactions between hydrogen bonds of amino acidsb. Helix arrangement—coiled structurec. Pleated sheet arrangement—chains that fold back upon themselves

3. Tertiary structurea. Three-dimensional configuration of amino acid chainb. Interactions among different R groups of the chain

4. Quaternary structure—individual polypeptides linked together5. Proteins whose shape is disrupted are said to be denatured

â Lecture Activity 2.5: Protein Structure and Function

2.9 What Are Nucleic Acids?A. DNA and RNA, the Molecules of Heredity, Are Nucleic Acids (Figure 2-26)

1. Nucleic acids—long chains of subunits known as nucleotidesa. Five-carbon sugarb. Phosphate groupc. Nucleotide base

2. DNA—deoxyribonucleic acid—contains deoxyribose nucleotides3. RNA—ribonucleic acid—contains ribose nucleotides

B. Other Nucleotides Perform Other Functions1. Cyclic nucleotides—intracellular messengers (ex. cyclic AMP)2. Adenosine triphosphate—carries energy from place to place (ex. ATP)

â Lecture Activity 2.6: Molecular Twenty Questionsâ Web Animation: Functions of Macromolecules

Improving on Nature? Revisited

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KEY TERMSacid cohesion ion polar moleculeamino acid covalent bond ionic bond proteinatom dehydration synthesis isotope protonatomic nucleus denature lipid radioactiveatomic number electron molecule solventbase electron shell neutron surface tensionbuffer element nonpolar molecule waxcarbohydrate functional group nucleic acidchemical bond hydrogen bond organic moleculechemical reaction hydrolysis pH scale

ANSWERS TO TEXT QUESTIONS

Figure-based Questions

Figure 2-2 Why do biologically active atoms tend to be ones whose outer shells are not full?

Atoms with partially empty outer shells have a strong tendency to react with other atoms in ways that gain or share electrons to fill their outer shells, or that give up electrons to empty their outer shells.

Figure 2-6 In water’s polar bonds, why is oxygen’s pull on electrons stronger than hydrogen’s?

Oxygen’s nucleus has eight protons, while hydrogen’s has only a single proton. So the positive charge of the oxygen nucleus attracts electrons far more strongly than that of the hydrogen nucleus.

Figure 2-8 Why is it important to human physiology that sugars dissolve easily in water?

Cellular energy is derived from the chemical bonds in sugar molecules. Blood, the fluid surrounding each cell, and cytoplasm consist largely of water, so the solubility of sugar in water allows sugar molecules to be transported to and into all of the body’s cells.

Figure 2-11 How would the concentration of hydrogen ions in a cup of tea change if you added lemon juice to it?

The pH of lemon juice is lower than the pH of tea, so the hydrogen ion concentration would increase.

Figure 2-15 Many types of plastic are composed of molecules derived from cellulose, but engineers are working hard to develop plastics based on starch molecules. Why might starch-based plastics be an improvement over existing types of plastic?

Starch is easily digested by decomposer microbes, so starch-based plastics would be far more biodegradable than plastics made from more microbe-resistant molecules such as cellulose.

Figure 2-24 Why do most proteins, when heated, lose their ability to function?

The hydrogen bonds that account for secondary and higher level protein structure can be broken by heat. Because a protein’s function generally depends on its shape, breaking shape-controlling bonds disrupts function.

Consider This

Some experts argue that we should encourage people to use artificial sweeteners and fake fats, because obesity will decline if people eat appealing food while limiting fat and sugar consumption. Critics of fake foods, however, contend that people should avoid the risks associated with artificial food additives and, instead, consume nutritious foods that are naturally low in sugar and fats. What do you think?

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Hints: Research the risks of obesity and of food additives that reduce calories. Research the effectiveness of the additives in helping people lose weight. Also consider whether it is possible to promote behavior that avoids both kinds of risks.Fill-in-the-Blank

1. An atom that has lost or gained one or more electrons is called a(n) ________. If an atom loses an electron it takes on a(n) ________ charge. If it gains an electron it takes on a(n) ________ charge. Atoms with opposite charges attract one another, forming ________ bonds.

ion; positive; negative; ionic

2. In addition to protons, all atoms except hydrogen have ________ in their nuclei. Atoms of the same element that differ in the number of neutrons in their nuclei are called ________ of one another. Some of these atoms spontaneously break apart, releasing ________ and forming different atoms in the process. Such atoms are described as ________.

neutrons; isotopes; energy; radioactive

3. An atom with an outermost electron shell that is either completely full or completely empty is described as ________. Atoms with partially full outer electron shells are ________ and may gain, lose, or share electrons, forming ________.

inert; reactive, chemical bonds

4. Water is described as ________ because each water molecule has partial negative and positive charges. This property of water allows water molecules to form ________ bonds with one another. The bonds between water molecules give water a high ________ and result in surface tension.

polar; hydrogen; cohesion

5. Large biological molecules are often formed from a series of similar smaller molecules that are linked together. The chemical reaction that creates bonds between the smaller subunits by removing water is called ________. The reverse reaction that breaks down these molecules by adding water is called ________. Starch and cellulose are both formed from subunit molecules of ________, and proteins are formed from ________.

dehydration synthesis; hydrolysis; glucose, amino acids

6. The four general classes of biological molecules are: ________, ________, ________, ________.

After each molecule, identify the general class to which it belongs:

cellulose: ________; steroid: ________; enzyme: ________; fat: ________;

disaccharide: ________; DNA: ________; glycogen: ________.

carbohydrates, lipids, proteins, nucleic acids; carbohydrate; lipid; protein; lipid; carbohydrate; nucleic acid; carbohydrate

Review Questions

1. Distinguish atoms from molecules; elements from compounds; and protons, neutrons, and electrons from each other.

An atom is the smallest particle of an element that still retains the properties of that element. A molecule consists of two or more atoms chemically bonded together. Protons are positively charged subatomic particles found in the atomic nucleus. Neutrons are uncharged subatomic particles found in the atomic nucleus. Electrons are negatively charged subatomic particles found in electron shells around the atomic nucleus.

2. Compare and contrast covalent bonds, ionic bonds, and hydrogen bonds.

Covalent bonds are formed by sharing electrons between two atoms. Ionic bonds result when oppositely charged ions attract one another. The charges on the atoms result from the transfer of one or more electrons from one atom to another to fill or empty the outer electron shell.

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3. Describe how water dissolves a salt.

The polar water molecules are attracted to the charged ions. The water molecules surround and insulate the ions from one another, allowing the ions to separate.

4. Define acid, base, and buffer. How do buffers reduce changes in pH when hydrogen ions or hydroxide ions are added to a solution? Why is this phenomenon important in organisms?

An acid is a substance that releases hydrogen ions when dissolved in water. A base is a substance that combines with hydrogen ions in water. A buffer is a compound that tends to maintain a solution at a constant pH by accepting or releasing hydrogen ions in response to small changes in hydrogen ion concentration. Small changes in pH from normal levels found in the body can interfere with the structure and proper functioning of biological molecules.

5. Which elements are common components of biological molecules?

The three most abundant atoms are carbon (C), hydrogen (H), and oxygen (O); nitrogen (N) is also relatively common (found in all amino acids and nucleic acids), and phosphorus (P) is present in nucleic acids and ATP.

6. List the four principal types of biological molecules, and give an example of each.

Carbohydrates—glucose, sucrose, starch, glycogen, cellulose, chitin

Lipids—oils, fats, waxes, cholesterol

Proteins—keratin, silk, hemoglobin

Nucleic acids—DNA, RNA

7. What roles do nucleotides play in organisms?

Nucleotides are subunit monomers in DNA and RNA; ATP serves as a short-term energy storage molecule; cyclic AMP is an intracellular messenger.

8. Distinguish among the following: monosaccharide, disaccharide, and polysaccharide. Give two examples of each and their functions.

A monosaccharide is a single sugar molecule; glucose and ribose are examples. Monosaccharides provide energy and serve as a building block for polysaccharides. A disaccharide is two monosaccharides bonded together; sucrose and lactose are examples. Disaccharides are used for short-term energy storage. A polysaccharide is a long chain of bonded monosaccharides; cellulose and glycogen are examples. Polysaccharides are used for long-term energy storage, and many are structural components of cells.

9. Describe the manufacture of a protein from amino acids.

Proteins are produced by dehydration synthesis of amino acids to form polypeptides bonded together by peptide bonds.

Applying the Concepts

1. IS THIS SCIENCE? Headlines on a magazine cover proclaim: “Turn fat into muscle!” Evaluate this claim from a scientific standpoint.

Hints: Fat tissue consists mostly of fat molecules, and muscle tissue consists mostly of protein molecules. Do they contain all of the same kinds of atoms?

2. Drugstores sell many different brands of “antacid” remedies, which are intended to bring relief from “acid stomach.” Each brand claims to eliminate symptoms faster than its competitors. How do these compounds work? Use your knowledge of acids, bases, and buffers to design an experiment to determine which brand of antacid works best.

Hints: Antacids may work by being basic and neutralizing stomach acid or by buffering the stomach contents at a pH that is normal for the stomach. Experiments might involve mixing fixed amounts of different antacids into solutions with

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acidity in the range found in stomachs and seeing how much the pH changes. Trials with different starting pH would help make the experiments more revealing.

3. Many of water’s unique properties are the result of its polar covalent bonds, which allow water molecules to form hydrogen bonds with each other. What if water molecules instead had nonpolar covalent bonds? Using information from this chapter, make a list of hypotheses about the ways in which this change might affect the properties of water. Describe how each change would affect living things. Design an experiment to test one of your hypotheses.

Hints: If water molecules were nonpolar, there would be no hydrogen bonds between water molecules. As a result, we might hypothesize that water would be less effective as a solvent, and that it would have less internal cohesion. Think about how such changes would affect such biological processes as transport of substances in blood and movement of water and nutrients in plants.

FOR MORE INFORMATION

Atkins, P. W. Molecules. New York: Scientific American Library, 1987. A layperson’s introduction to atoms and molecules, with superb illustrations.

Burdick, A. “Cement on the Half Shell.” Discover, February 2003. Mussels produce a protein polymer that is waterproof and incredibly strong.

Goodsell, D. S. The Machinery of Life. New York: Springer, 1993. Goodsell depicts the molecules of a cell in all their three-dimensional, interactive glory. A great way to gain a feel for the beauty and intricacy of the organic molecules of life.

Hill, J. W., and Kolb, D. K. Chemistry for Changing Times. 10th ed. Upper Saddle River, NJ: Prentice Hall, 2004. A chemistry textbook for nonscience majors that is both clearly readable and thoroughly enjoyable.

King, J., Haase-Pettingell, C., and Gossard, D. “Protein Folding and Misfolding.” American Scientist, September–October 2002. Protein folding holds the key to proteins’ diverse functions.

Kunzig, R. “Arachnomania.” Discover, September 2001. Researchers work to unravel the mystery of spider silk protein and develop a process to synthesize it.

Morrison, P., and Morrison, P. Powers of Ten. New York: W. H. Freeman, 1982. A fascinating journey from the universe to the nucleus of an atom.

LECTURE ACTIVITIES

Lecture Activity 2.1: Exercise in Chemical Bonding

Estimated Time to Complete: 10–20 minutes

IntroductionThis activity is a basic introduction to the concept of chemical bonding. This is a short, in-class exercise that can follow an introductory discussion of atomic structure and bonding. Students will take the number of their birth month as their atomic number. Given this information, they will be able to determine the configuration of electrons. They will then be able to determine how this atom will interact with other atoms, if at all. Students will form groups with other students to form ions or molecules and will present their bond formation to the class.

Chapter Section Reference2.2 How Do Atoms Form Molecules?

Materials Needed Pen Paper

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Procedures1. Instruct the students to identify their birth month on a piece of paper. They will consider the number of their birth

month to be their atomic number.2. Next, instruct them to draw their appearance as an atom. Specifically, they must determine their electron configuration

and how many electrons are in their outermost shell.3. Using this information, they should determine what type of bond they might like to form to become stable and fill the

outermost shell.4. Students must then form a bond with another classmate so that both “atoms” become stable.5. These student groups of bonded atoms can then present their bond to the class and explain why they are both now

stable. Alternatively, to save class time, they could write this information on a sheet of paper to be handed in.

Assessment SuggestionsEvaluate the student bonds that are formed and assign a grade for class participation.

Lecture Activity 2.2: Atomic Love Connection

Estimated Time to Complete: 20 minutes

IntroductionThis activity reinforces students’ understanding of atomic structure, as well as ionic and covalent bonds. These topics should be covered in class prior to beginning this activity. In this activity, the students will either choose or be assigned a particular element and will write a “personal ad” for that atom. This ad should describe the properties of the atom and also describe what type of bond the atom would “like” to form. Following completion of the handout, students should share their “ads” with each other to find a good bonding match between atoms.

Chapter Section Reference2.2 How Do Atoms Form Molecules?

Materials Needed Handout included in this activity Periodic table for the entire class or for each student Pen or pencil

Procedures1. Hand out worksheet with background information.2. Students should work individually to write their own personal ad for their atom. The instructor may choose to assign an

element or students may choose from the elements listed on the worksheet. In larger classes, more than one student can be assigned the same element.

3. The students should first determine the atomic number of their element and how many electrons are in the outer shell. This information can then be used to determine if the atom is most likely to form a covalent or ionic bond.

4. Students can then interact with each other in groups to find matches to their ads. For example, a carbon ad would match up well with a hydrogen ad to form covalent bonds.

Assessment SuggestionsYou may collect the student’s sheets for grading or assign an in-class participation grade if the student reads their ad to the class.

Lecture Activity 2.3: Carbohydrate Reverse Questions

Estimated Time to Complete: 20 minutes

IntroductionThis activity allows the students to begin to think about carbohydrates in preparation for an exam or quiz. You can explain to your students that this may not be a bad way to study, not just for the carbohydrates, but for any topic.

22 Instructor Guide

Chapter Section Reference2.6 What Are Carbohydrates?

Materials Needed Pen Paper

Procedure1. Break the students up into groups of three or four.2. Instruct each group to take approximately 5 minutes to create three to four carbohydrate questions that have one or two

word answers. Have the groups write down the questions and answers.3. Have each group select their best (or favorite) question and give the answer to the class as a whole. Give the class time

to come up with the question that matches the answer presented.

Assessment SuggestionsYou can have the groups turn in their questions and consider using a few on the exam.

Lecture Activity 2.4: Fake Fats: To Eat or Not to Eat?

Estimated Time to Complete: 20 minutes

IntroductionThis activity allows students to engage in a debate related to the real-life issues surrounding the use of the fat substitute Olestra. Students are assigned to two opposing groups: one in favor of the use of fake fats and the other against the use of fake fats. They are given Web links to different sources of information. This debate announcement can be posted on the course Web page on the day the details of the debate are introduced to the class. Alternatively, the debate announcement and details can be distributed as a handout to the students. At the end of the debate, students will take part in a “taste test” to sample chips made with “real fat” versus “fake fat.”

Chapter Section Reference2.7 What Are Lipids?

Materials Needed Debate announcement/handout Regular and Olestra-containing potato chips for taste test

Procedures1. The students are given this assignment in the class before the debate is to occur. Before the debate, the students must

gather information to support their argument for the debate. Part of this preparation involves understanding the structural differences between fake fats and real fats.

2. On the day of the debate, they are given approximately 5 minutes to meet with others on their “side” to come up with their game plan for the debate.

3. When the debate begins, the two groups take turns presenting their arguments either for or against the use of fat substitutes. The debate lasts about 15 minutes. The instructor keeps track of each side’s arguments on the board and, at the end, the students are given time to copy down what is on the board.

4. After the debate, the students take part in a taste test of potato chips made with “real fat” and “fake fat.” During the taste test, the instructor reiterates the important points of the topic and revisits the structural comparison between the fake fat molecule and the real fat molecule. The students should offer their opinions about the taste differences and how they relate to the structural differences between the two molecules.

Assessment SuggestionsA. One option for assessment is to assign the following:

1. To hand in: (no more than one page)a. State which side of the debate you were on.b. List two reliable resources that you used to prepare for this debate.c. List at least two arguments on your side of the debate.

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B. Another option involves either assigning the following questions for homework or including them as essay questions on an exam:1. Your aunt calls you because she has heard a report about Olestra on the news. The news report has raised her

concern about using products containing Olestra. She knows you are taking a biology class and hopes you can provide some facts. Write a short note to your aunt filling her in on the pros and cons of using Olestra, based on the information you learned in class. Let her know what your conclusions are AND what scientific facts you have based these conclusions on.

2. Explain how the structure of a fake fat is different from that of real fat. Why does this make a difference in the digestive system? Additionally, explain how this structure is related to the debate over the use of fake fats in foods.

Lecture Activity 2.5: Protein Structure and Function

Estimated Time to Complete: 20 minutes

IntroductionThis activity allows students to learn more about the science of protein structure analysis. A great deal of biological research is now focused on determining the structure of different proteins. Scientists then use that information to generate hypotheses about the function of that protein. In this exercise, you will display three different three-dimensional protein structures and ask the students to describe the structure and then make predictions about possible functions of that protein based on its structural characteristics. The students may work individually or as part of a team to complete the exercise. Included in this activity are three Web sites with pictures of particular protein structures. Additionally, a set of three PowerPoint slides containing the specific pictures and their Web site sources is included.

Chapter Section Reference2.8 What Are Proteins?

Materials Needed Computer with projector capabilities (or the pictures can be copied onto overhead transparencies) Pen and paper

Procedures1. Advise the students that you will be presenting them with two pictures of proteins for which scientists have determined

the structure.2. For each of the proteins, the students should first write down their observations of the protein’s structure. Ask the

students: How would you describe what you see in your own words?3. Now, working in small groups, the students should try to determine the function of each protein. They should state their

hypothesis AND the reasoning behind their hypothesis. Explain that they will not be graded based on a right or wrong answer. Instead, they should put themselves in the place of scientists who are currently working on these same problems. Encourage them to be creative!Here are the links for the two pictures to be used (alternatively, you may use the PowerPoint slides that are included):A. www.biologie.uni-konstanz.de/folding/Structure%20gallery%201.htmlB. www.msi.umn.edu/general/Bulletin/Vol.14-No.1/Protein.html

Instructor’s guide for protein structures:1. This is a picture of outer membrane proteins that are “tunnels” used to transport items in and out of bacterial cells. This

is a side view, but if you were to look from the top, you would see that these proteins form circular channels for moving molecules.

2. This is a helicase protein that interacts with DNA (shown in the picture). Scientists determined that the opening of this ring-shaped protein could accommodate the DNA molecule. This protein plays a role in unraveling a DNA molecule during DNA replication.

Assessment SuggestionsYou may collect the sheets containing the students’ observations and hypotheses. Alternatively, you may assign the students to go online to find a recent study that identified the structure of a protein. They can then write a short paragraph about the significance of the study.

24 Instructor Guide

Lecture Activity 2.6: Molecular Twenty Questions

Estimated Time to Complete: 15–20 minutes

IntroductionIn this activity, the students will get an opportunity to test their knowledge of biological molecules. The students will form groups of three or four. Each student will draw the name of a biological molecule from a hat. The other students in the group will then take turns asking yes or no questions until one of them is able to correctly guess the identity of the molecule in question.

Chapter Section Reference2.9 What Are Nucleic Acids?

Materials Needed Names of different molecules on pieces of paper for each student to draw (The sheet included with this activity contains

the names of a few molecules that can be used in this exercise. You can cut out the names from this sheet to use in class. For a larger class, you may repeat the same molecules.)

Hat or box to place names in

Procedures1. Instruct the students to form groups of three or four students. Explain how the game will work and have the students

determine who will go first in each group.2. Allow one member from each team to draw the name of a biological molecule from the hat.3. The other members of each group must then take turns asking a yes or no question about the molecule.4. If a student in a group guesses correctly, they must wait until their turn to answer.5. Each member of the group must take a turn drawing the name of a molecule for the others to guess.6. This is a useful means of reviewing for an exam that is not time consuming.

Assessment SuggestionsYou may have the students keep track of how many they guess correctly and give out a grade or extra credit for those who get above a certain score.

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.1 Handout—Exercise in Chemical Bonding1. Write the number of your birth month: ________ The corresponding element is: __________

2. Draw your atom. The number of electrons in the outermost shell is: ________

3. Which element or elements would you bond with?

4. Find at least one classmate who has the atom you need. That classmate is: _______________.

5. Briefly explain why bonding with the above classmate’s element has made both atoms stable.

1

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.2 Handout—Atomic Love ConnectionChoose one of the following elements:

carbon magnesium hydrogennitrogen chlorine calciumoxygen sodium phosphorussulfur potassium bromine

1. Determine the atomic symbol: ___________

2. Use the periodic table to determine the atomic number: ___________

3. Describe how you will determine if the atoms of your element are inert or reactive.

4. Use the characteristics of your atom to write a “personal ad” for it. Be creative! See the example below as a guide for the information you should include.

Example: Fluorine (F); atomic number = 9Personal ad: Single fluorine atom seeking another kind atom willing to donate one electron to add stability to my life. I currently have seven electrons in my outer shell and am willing to form an ionic bind with any atom who answers this ad.

5. When you are done, see if you can find another personal ad that is a good match for yours (your atomic love connection). Write your match below. What kind of bond will you form?

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.3 Handout—Carbohydrate Reverse Questions1. Write your three or four questions and their one to two word answers.

2. Select your best question from the list above. Read the ANSWER to the class. Did anyone come up with your question? Did anyone come up with a question that matches your answer? If so, what was the other question?

3. Were you able to develop a question for any of the other answers from other groups? If so, what was it?

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.4 Handout—Fake Fats: To Eat or Not to Eat?

For this debate: You must research the scientific and medical arguments on your side. You should also research what the arguments will be on the other side, so that you are prepared to argue against

their points.

Start your debate prep by visiting the sites below:

Center for Science in the Public Interest (www.cspinet.org/olestra/index.html) are against fake fats; Proctor and Gamble (www.olean.com/), the makers of Olean, are in favor of fake fats

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.5 Handout—Protein Structure and Function1. For each of the proteins your group is assigned, make your observations. What do you see and what do you not see?

2. What is your hypothesis regarding the function of each? What support do you have to defend this hypothesis?

3. If your instructor has a class discussion after the groups have met, are there any ideas that your group did not originally think about? Does that alter your hypothesis? Why or why not?

Name: __________________________ Date: __________________

Instructor: ______________________ Course Section: _________

Lecture Activity 2.6 Handout—Molecular Twenty Questions

DNA Glucose Cholesterol

RNA Phospholipid Starch

Lactose Sucrose Protein

Amino acid Nucleotide Lipid