This Document Contains Chapters 1 to 3 CHAPTER 1: THE SCIENCE OF BIOLOGY WHERE DOES IT ALL FIT IN? Chapter 1 is a diverse keystone chapter that outlines the scope of information being covered in the rest of the book. Reinforce to students that the concepts of evolution, hierarchy, living properties, and scientific method are essential for understanding the other chapter topics covered throughout the semester. It may be fitting to refer to Chapter 1 when discussing the different levels of organismic complexity covered in the following chapters. It is also important to stress that the information discussed in each chapter was derived from careful scientific inquiry using the principles of scientific method covered in Chapter 1. SYNOPSIS Biology is the science of life, the study of ourselves and everything that is alive around us. Living things have a specific organization presented here from smallest (atoms) to largest (the biosphere). Living organisms have cellular organization; are ordered; respond to stimuli; grow, develop, and reproduce; take in energy to perform many kinds of work; and they have regulatory mechanisms that coordinate functions and maintain constant internal conditions. A sound knowledge of biology is necessary to make informed decisions regarding our individual and collective futures on this planet, and indeed, on the future of the earth itself. Darwin’s voyage around South America is one of the best examples of the process of scientific discovery. It explains how inductive reasoning leads to the formulation of hypotheses that are then tested by observation and experimentation. With continued collection of supporting data, some hypotheses prove strong enough to warrant their acceptance as theory. Darwin based his concept of evolution upon years of his own observations as well as those of his contemporaries. The writings of others, particularly Lyell and Malthus, strongly influenced him. Publication of On the Origin of Species was greatly delayed, in part because of its revolutionary nature. A similar essay by Wallace, sent to Darwin for approval, stimulated Darwin to publicly present and finally publish his ideas. A wealth of information gathered in the past century provides the impetus for scientists to accept evolution as a valid theory. Four core themes unite biology as a science: (1) living things all exhibit cellular organization, (2) living things all exhibit a mechanism for heredity (DNA), (3) living things exhibit adaptations to produce unique features as a result of evolution, and (4) living things conserve key features during evolution. LEARNING OUTCOMES 1.1 The Diversity of Life Is Overwhelming 1. Describe the six kingdoms of life. 1.2 Biology Is the Science of Life 1. Describe five fundamental properties of life. 2. Describe the hierarchical nature of living systems. 3. Discuss how living systems display emergent properties. 1.3 Science Is Based on Both Observation and Reasoning 1. Distinguish between deductive and inductive reasoning. 2. Illustrate how experimentation can be used to test hypotheses. 3. Discuss how scientists use models to describe, explain, and test theories. 1.4 The Study of Evolution Is a Good Example of Scientific Inquiry 1. Describe ideas about evolution proposed before Darwin. 2. Identify important observations made by Darwin on the Beagle. 3. Describe Darwin’s theory of evolution by natural selection. 4. Identify how evolution has been tested over time. 1.5 A Few Important Ideas Form the Core of Biology 1. Describe seven unifying themes of biology as a science. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 1 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • Life is too complex to be explained with reasoning by reductionism. • All organisms must have every characteristic of life. • Acquired characteristics can be inherited. • Biologists have do not have a feasible explanation for the emergent properties of life. • All organisms have the same level of hierarchical organization. • There is no single list of steps called "The Scientific Method”. • Hypotheses are merely a guess about how nature works. • Theories are merely biased reasoning by scientists. • Theories do not change over time. • The control set-up is indistinguishable from the experimental set-up in an experiment. • Correlations provide the same information as cause-and-effect experimentation. • The use of scientific models is not accepted by much of the scientific community. • Evolution is a means of disproving the existence of a supernatural being. • Biological principles can be described without evolutionary theory as a basis of the explanations. • Flaws in Darwin’s reasoning weaken the scientific theory of evolution. • Evolution only occurs on the individual organism level. • Evolutionary adaptation occurs during the lifetime of an organism • The death of an individual organism can change the whole fate of the Earth. • Basic research has little value in providing human applications of research findings. INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE It is only logical to present the material in this chapter at the beginning of an introductory biology course, whether it is a majors or nonmajors course, a one-semester or two-semester sequence. Unfortunately, there is so much information that we all feel must be covered in a beginning class, that it often turns into a memorization match rather than a learning experience. Don’t be compelled to cover every topic that is in this book. Nor should you expect your students to know every single fact presented here. Choose material you feel comfortable with; that is most appropriate to your locale and is timely and interesting; but yet fulfills the basic expectations of your department and your school. This chapter introduces biology as a science and the basics of the scientific method. Many prominent texts use Darwin’s evolutionary theory as an example of how science works. Many other topics could be presented as well, including Mendel’s genetics, Pasteur’s spontaneous generation, Jenner’s smallpox vaccine, or your own research. (Be careful not to get too involved if you do discuss your own research interests. You are an expert on the topic, but many of these students don’t know anything about even basic biology yet.) It may help to differentiate between inductive and deductive reasoning by deriving the words themselves. Humor is also helpful in presenting the scientific method, especially in terms of constructing readily rejected hypotheses. It is extremely important to present the difference between a scientific theory and a belief. One can believe in all sorts of things and still fully support the facts presented by science. Such a presentation will help the student who feels that much of science, such as evolution and the origin of life, contradicts his or her most inner personal beliefs. HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluate information from Chapter 1. Application • Have students apply the concept of homeostasis to explain the difference in characteristics between a living and a dead animal. • Have students apply the scientific method to design an experiment explaining the claim that a dietary supplement called Compound X improves a person’s alertness. • Ask students to hypothesize about the evolutionary mechanism explaining the evolution of a flying dragon’s bones for a fictitious discovery in England. Analysis • Ask to students to describe how Darwin might explain the discovery of ancient human fossils if he came across them on his travels on the Beagle. • Ask students to select and evaluate the four most important characteristics of life needed to verify the probability of identifying a living organism on another planet. • Have the class analyze whether the characteristics of life equally apply to animals, microorganisms, and plants. Synthesis • Ask students to come up with a list of conditions that would reduce the chance of evolutionary change in a population of organisms over thousands of lands. • Ask students to predict how a physician would treat an infection if the core theme of Cell Theory was never discovered. • Have students explain how a toxic chemical released into a lake would affect each level of hierarchy associated with the hierarchical organization of the lake. Evaluation • Ask students discuss the value of evolutionary theory in preparing vaccines against a global outbreak of bird flu. • Ask students to determine if the discovery of fossils is essential for supporting the principles of modern evolutionary theory. • Have students evaluate the basic biological principles they would need to determine the impacts of exterminating all houseflies in their city. VISUAL RESOURCES 1. Direct the class through a quick exercise of the scientific method by bringing in a simple mechanical object that does not work, like a flashlight. Discuss with the class the process of the scientific method needed to diagnose what is wrong and needed to fix it. (This does presume that you do know what is wrong and have the parts to make it good.) 2. Use a quick demonstration to stress that science is constantly changing. As life has evolved, so has the study of it. Too often science is presented as just so many facts; students don’t appreciate that a few of their instructors were born before the nature of DNA was determined. The technology of science is so overwhelming that the essence of science is often lost. 3. It may be helpful to present controls, independent, and dependent variables using the students’ first laboratory exercise as an example. It is important that they know what a controlled experiment is and why controls are included in their own laboratory experiments. When asked, many students will identify just a single test as a control. In reality an entire experimental set usually has several control runs and only one true experimental test associated with it. A useful activity to reinforce these concepts is to ask the class to design a controlled experiment to test the following observation: A high degree of birth defects was noted in fish living in water contaminated with mercury from a chemical company. Ask the students to come up with an experiment to determine if the mercury pollution is causing the problems in the fish. 4. Slides illustrating the kinds of organisms observed by Darwin during his voyage are quite helpful. Include examples of diversity in selectively bred plants or animals (varieties of corn, dairy and beef cattle, fancy goldfish) as well as examples of the similarity of island life forms versus mainland forms. Images can be found by doing a Google Image search using the keywords “Darwin’s Finches”, “Darwin Pigeons”, “Fancy Goldfish”, “Cattle Breeds”, and “Corn Varieties”. Also, the National Health Museum has a hands-on student activity called The Beaks of the Finches that uses Darwin’s Finches to reinforce the rationale he used for developing the natural selection theory. The activity can be found at http://www.accessexcellence.org/AE/AEC/AEF/1996/sprague_beaks.html IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Modeling Life Properties with Elodea Introduction Elodea, and aquatic plant, provides a simple model for investigating some of the properties of living organisms. It has large cells that can be clearly projected on a screen using a 400X microscopic specimen placed on a wet mount slide. This activity demonstrates how almost all organisms show at least one characteristic of life covered in Chapter 1. Materials • 1 stem of fresh elodea (available at pet stores or biological supply companies) • 1 forceps • 1 projector microscope or microscope attached to a video projector • 1 microscope slide • 1 small bottle of cold water with a dropper • 1 small bottle of 50oC water with a dropper • 1 small bottle of room temperature 3% hydrogen peroxide with a dropper • 1 small bottle of room temperature pure methanol with a dropper Procedure 1. Remove a leaf of the elodea using a forceps 2. Transfer the leaf to a microscope slide containing three drops of cold water 3. Place the slide under the microscope and focus the image under high power so the chloroplasts can be clearly seen 4. Ask the students if they observe any properties of life (some may answer cell structure or organization) 5. Add the 50oC water to the slide and ask the students to observe what happens. After a while the chloroplasts should move. Then ask the students if they observe any properties of life (some may answer metabolism, movement, or response to stimuli) 6. Add one drop of 3% hydrogen peroxide to the slide and ask the students to observe what happens. They should see bubbling due to catalase activity. Then ask the students if they observe any properties of life (some may answer metabolism or response to stimuli) 7. Add one drop of strong brewed coffee to the slide and ask the students to observe what happens. They should see the bubbling activity stop due to inhibition of catalase activity and they may see the chloroplasts stop moving. Then ask the students if they observe any properties of life (they should explain that the characteristics of life observed earlier were ceased by environmental change) Inquiry Questions 1. Ask the students how they would test whether the yeast found in a package of freeze dried yeast found in the grocery store are still alive. Answer: Dissolve the yeast in warm sugar water and wait 10 minutes. If it bubbles or froths, the yeast is alive. 2. Ask students to come up with tests to determine the relative amount of living properties present in a sprig of celery found in a grocery store. Answer: Check if the celery becomes firmer when placed in water (turgidity test), see if dye moves through it, or examine it under a microscope for intact cell structures. 3. Ask students to come up with a definition of “dead” based on the fact that extinct animals can be cloned from DNA found in museum specimens. Answer: "Dead" means an organism has ceased all life functions, though its DNA might still be viable for scientific processes like cloning. LABORATORY IDEAS Laboratory activities are excellent ways of reinforcing complex biological principles. The following inquiries can be used as the basis of student-designed laboratory activities. A. Characteristics of Life: a. Have students design a long-term experiment to distinguish between the characteristics of fresh and cooked potato wedges containing at least one “eye” per section. b. Provide students with the following materials to carry out the experiment. i. Ruler ii. A small pot with soil iii. Access to a light source iv. Hydrogen peroxide in a dropper bottle to indicate the presence of catalase metabolism v. Potassium iodide solution in a dropper bottle to indicate the presence of starch vi. pH paper to determine the pH of the plant tissues B. Scientific Method: a. Have students design an experiment to test the cause-and-effect relationship between physical activity and heart rate. b. Provide students with the following materials to carry out the experiment. i. Stop watches to monitor pulse (heart rate) ii. A location for students to conduct some type of physical activity such as jogging or stair climbing. iii. Graph paper or access to software for graphing the relationship between heart rate and physical activity for the whole class. c. Then ask the students to consider other variables that could affect the results. Provide them with the following materials to conduct this part of the experiment. i. Body weight scale ii. Meter stick iii. Tape measure C. Natural Selection: (Precaution – this lab involves the tasting of substances in class) a. Have students hypothesize about the natural selection of human taste by researching their findings from a PTC taste paper experiment. b. Provide students with the following materials i. PTC paper (phenylthiocarbamide) ii. Clean fresh cabbage iii. Strong coffee iv. Food grade honey v. Clean disposable spoons for tasting honey and coffee vi. Access to the Internet c. Ask students to determine the students who can and cannot determine the taste of phenylthiocarbamide in the PTC paper. d. Then ask them to see if the ability to taste or not taste phenylthiocarbamide is related to a person’s like or dislike of the taste of cabbage, coffee, or honey. e. Have the students research the web to find any evidence of the ability to taste phenylthiocarbamide and the preference of certain types of foods. f. Follow step “e” by having the students hypothesize about the natural selection of phenylthiocarbamide tasting in certain populations of people. LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. Students who have successfully mastered the content of Chapter 1 can apply their knowledge for service learning activities in the following ways: 1. Have students give presentations about the Hierarchy of Life at an area nature center. 2. Have students visit a local elementary school to give a presentation on the properties of life. 3. Have students judge science fairs that focus on projects that emphasize use of the scientific method. 4. Have students prepare a poster or display depicting the influence of Darwin on modern scientific thought for an area library or local children’s museum. ETYMOLOGY OF KEY TERMS bio- life or relating to living organisms (from the Greek bios- mode of life) carya- see karyo below eu- good; well; true (from the Greek eu- well) homeo- likeness; resemblance; similarity (from the Greek homoios- like) karyo nucleus of a cell (from the Greek karyon- nut or kernel) -logy a field of study; an academic discipline; the study of (from the Greek logos- word) meta- change; transformation; following something in a series (from the Greek meta- change) photo- light (from the Greek photos- light) pro- before; for; in front of (from the Greek and Latin pro- for or before) stasis unchanging (from the Greek stasis- standing) synthesis to make or assemble (from the Greek synthesis- placing together) CHAPTER 2: THE NATURE OF MOLECULES AND THE PROPERTIES OF WATER WHERE DOES IT ALL FIT IN? Chapter 2 investigates the fundamental principles of chemistry making up the first hierarchy of living system. It can be an overwhelming chapter because of the diversity of concepts needed to build an understanding of biological molecules and their molecular environment. Reinforce to students that the chemistry being covered in this chapter is essential for understanding cell structure and organismic function, and principles of homeostasis being taught during the semester. Regularly refer to Chapter 2 when discussing the topics that rely on knowledge of molecules and the properties of water. SYNOPSIS A basic understanding of chemistry is necessary to the study of biology because the two are inexorably intertwined. Living organisms are chemical machines composed of molecules that continually undergo chemical reactions to become new molecules. Atoms are composed of protons, neutrons, and electrons. Each subatomic particle has its effect on the chemical identity and interactivity of each element with all other elements. Formation of molecules from elements depends primarily on the tendency of electrons to occur in pairs, balance positive and negative charges, and fill the outermost shell. Chemical bonds result from trading or sharing electrons; shared bonds are stronger because they require the continued close proximity of atoms to one another. Water, a simple but elegant molecule, predominates in living organisms and is unique in the life-giving characteristics stemming from its polar nature. Water clings to other polar molecules (adhesion), as well as itself (cohesion), by forming transient hydrogen bonds. These bonds absorb thermal energy, consequently the presence of water has a moderating effect on temperature changes. It is also a powerful solvent for other polar molecules and excludes nonpolar molecules, enabling the formation of biological membranes. LEARNING OUTCOMES 2.1 All Matter Is Composed of Atoms 1. Describe the structure of the Bohr atom. 2. Relate the arrangement of electrons in an atom to its chemical behavior. 3. Explain how energy is quantized in atoms. 2.2 The Elements in Living Systems Have Low Atomic Masses 1. Relate the periodic table to the chemical reactivity of different elements. 2.3 Molecules Are Collections of Atoms Held Together by Chemical Bonds 1. Explain how ionic bonds promote crystal formation. 2. Explain how covalent bonds hold atoms together. 3. Predict which kinds of molecules will form hydrogen bonds with each other. 4. Distinguish between a chemical bond and van der Waals attractions. 5. Identify three factors that influence which chemical reactions occur within cells. 2.4 The Properties of Water Result from Its Polar Nature 1. Explain how the structure of water leads to hydrogen bond formation. 2. Distinguish adhesion from cohesion. 3. Explain why water heats up so slowly. 4. Explain why sweating cools. 5. Explain why ice floats. 6. Explain why salt dissolves in water. 7. Explain why oil will not dissolve in water. 2.5 Water Molecules Can Dissociate unto Ions Calculate the pH of a solution based on the molar concentration of H+. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 2 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • Mass and volume both describes the amount of matter • Mass and weight are the same and they are equal at all times • The density of an object depends only on its volume • The temperature of an object drops when it freezes • Particles of solids exhibit no motion • Atoms can be seen with a standard microscope • The terms atoms and elements are synonymous in meaning • The atomic nucleus is large and in close proximity to the orbitals • Atoms have electrons circling them like planets the sun • The electron shell is there to protect the nucleus • Elements of solids are hard, whereas elements of gases are soft • Gas molecules weigh less than solid molecules • Atomic mass values are affected by electron number • Molecules are glued together • All bonds store and release energy • The chemical bond is a physical thing made of matter • Ionic compounds form neutral molecules such as Na+Cl- in water • Electrons in colavent bonds belong to the particular atom they came from • Electron pairs are equally shared in all covalent bonds • The strength of acids and bases is the same thing as its concentration • Substances containing H are acidic; substances containing OH are basic • When a proton donor acid reacts, the nucleus of an atom loses a proton • The pH scale represents a linear change in measurement • Buffers make a solution neutral • All acids and bases are harmful and poisonous • Salts don't have a pH value • pH is a measure of acidity INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE This is the material that many prospective biology students abhor. After all, if they enjoyed this type of information they would be taking chemistry as an elective, not biology. Although most programs consider basic high school chemistry a prerequisite to introductory biology, fewer high schools offer such a course now than did ten years ago. As a result, part of the class will be bored if you get too basic and the other part of the class will be lost if you assume this chapter is a review. Try to find a happy medium. A short pretest on the material may help gauge the level of your students, and may surprise some who thought they knew the material. Many students have a math phobia as well as a chemistry phobia and have a difficult time with anything that has equations, plus, minus, and equal signs. pH is a difficult concept partly because of the invention of calculators; logarithms are ancient history. Stress that each number on the pH scale is different from its nearest neighbor by a factor of ten, like the Richter scale for earthquakes and the decibel scale for sound. Oxidation/reduction reactions cause problems as well; remember that reduced compounds add electrons and oxidized compounds lose electrons. This is one time that being reduced results in a gain! HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluated information from Chapter 2. Application • Have students apply the concept adhesion and cohesion of water to properties of glue. • Ask students to explain the why digestive system of animals must be adapted to break down covalent bonds yet there is no particular system for breaking down ionic bonds. • Ask students to explain why pH is a factor used in food preservation. Analysis • Ask students to explain what types of organisms would be most affected if their bodies took in an abundance of isotopes having a higher atomic mass. • Ask students to select and analyze the three characteristics of water that would help an organism survive in the desert. • Have the students explain why the “static cling” of dry clothing can be removed simply by spraying a mist of water on the clothing. Synthesis • Ask students to describe how an organism would have to adapt to environmental conditions where covalent bonds are easily broken. • Ask students to describe the properties of a medical device that can buffer blood without using any chemical buffers. • Ask students to devise the potential agricultural uses of an instrument that measures the types of elements found within an intact living organism. Evaluation • Ask students to discuss the probably of life a planet that is not abundant in the elements that form covalent bonds. • Ask students to explain which characteristics of life mentioned in Chapter 1 are determined by the properties of elements making up organisms. • Have students debate the belief that high energy magnetic fields produced by electrical power lines are harmful to organisms. VISUAL RESOURCES 1. Molecular models of are quite helpful when reinforcing the concept of molecular structure. Many aspects of chemistry such as the differences between isomers just don’t work on a two-dimensional surface. Use student participation and an inexpensive object such as a tennis ball to illustrate the difference between ionic and covalent bonds. When the object is given by one student to another, the recipient can walk away, no strings attached. This is similar to the exchange of electrons that form the ionic bond. When the object is held by both students, or shared as analogous to the covalent bond, the two students must remain in fairly close proximity for such sharing to be practical. 2. In a small class setting, bring in samples of polar and nonpolar substances and mix them together. In a large class, use an overhead or videocam with LCD setup to project it to the entire class; this may take a little ingenuity when working on a horizontal surface. So, it may be useful to conduct the demonstration in plastic Petri plates. Cohesion and adhesion can also be demonstrated in this manner using colored solutions and capillary tubes touched to the solutions. Diatec makes 35 mm deep well projection slides that are waterproof (available through Carolina or Wards Biological Companies). 3. Energy levels are similar to a person being on a pogo stick; they are either up or down, but not in between. Electrons can only change their energy in specific increments, by being up or down. This can be approximated by doing a bouncing action a few times with your feed planted on the floor. The action represents an electron in one energy state. Then represent an electron leaving and returning to its energy level by jumping high straight up and landing on the same spot with a thud. 4. The characteristics of water are intuitive when related to everyday events, tempering effects on weather, sweating, surface tension, and so forth. Use as many common examples as possible. Your students can measure the relative pH of various household solutions using tea – the normal unadulterated drinking variety. Tea becomes more yellow in color when lemon juice is added because the juice is acidic, not because the tea is diluted by a yellow liquid. Red cabbage is also an acid-base indicator, red when acid, blue when basic. 5. The following analogy has been quite helpful in differentiating ionic and covalent bonds. Mary is a well-prepared student who sits attentively in the front row during lecture. Normally she brings two cans of pop to lecture, orange and cola. Ann, a thirsty classmate, begs the cola from generous Mary and sits in the back row. The bond between the two students is analogous to an ionic bond. The can of pop is donated from one student to another. The bond strength between Mary and Ann is not very strong as they can sit on opposite sides of the lecture hall and still each drink a pop. David also comes to class with two cans of pop, root beer and lemon-lime. He, though, is less generous and less decisive than Mary and wants to drink both flavors of pop during lecture. When his thirsty friend Ed arrives, David decides to share his pop rather than overtly giving one can away. Ed must, therefore, sit in the seat right next to David. This is analogous to a covalent bond. David and Ed must remain in close proximity to one another and the bond between them is quite strong, especially in comparison to the ionic bond between Mary and Ann. IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Exposing the Carbon Skeleton of Organisms Introduction It is difficult for students to conceptualize the presence and significance of carbon that makes up the skeleton of all organic molecules. This demonstration shows the prevalence of carbon in carbohydrates and the amount of bond energy stored in organic molecules. It uses sulfuric acid to break down the covalent bonds of sucrose releasing the oxygen and hydrogen. What remains in the container is a carbon mass puffed with gases (carbon dioxide and sulfur oxides) released by the molecular degradation. Special Precautions Caution must be used with this demonstration. It produces a rapid burst of heat and noxious fumes. It should be done using personal protection equipment (gloves, goggles, and a laboratory apron) and in a well-vented area near a source of running water. Be careful to conduct the demonstration in a manner that students cannot be harmed if the glass container cracks. The waste remaining from the demonstration should be disposed in an acid waste container. This procedure can be shown to a large class using a videocam attached to an LCD projector. Materials • Large glass thermometer • 400 ml Pyrex® or equivalent glass beaker • Large glass test tube • 100 ml of water • Bottle of sucrose solution with dropper (20g sucrose/100 ml water) • Bottle of concentrated sulfuric acid solution with dropper • Roll of aluminum foil • Personal protection equipment Procedure 1. Explain to the class that you will be demonstrating the elemental composition of sucrose. 2. Lay down a sheet of aluminum foil on the table where the demonstration will take place. 3. Place the beaker in the middle of the foil 4. Add 100 ml of water to the beaker 5. Place the test tube into the beaker 6. Add 5 ml of sucrose solution to the test while explaining to your action to the class 7. Place the thermometer in the beaker so that the bulb is touching the base of the test tube 8. Announce to the class the starting temperature of the solution 9. Slowly add approximately 2 ml of the concentrated sulfur acid (do not mix or stir) 10. Direct the class to observe what happens (the solution will darken followed by the rapid eruption of a black column of “puffy material” 11. Announce to the class the final temperature of the solution Inquiry Questions 1. Ask the class to explain the elemental composition of the “puffy material” (they should be directed to answer, carbon with hydrogen gas and carbon dioxide). Answer: The elemental composition of the “puffy material” primarily includes carbon, hydrogen, and oxygen. In particular, it contains carbon combined with hydrogen gas and carbon dioxide. 2. Ask the class to explain the temperature elevation (they should explain it was due to the energy released by the breakage of covalent bonds) Answer: The temperature elevation is due to the energy released when covalent bonds in the material are broken. This process releases heat, resulting in the increase in temperature. 3. Ask the students what they should expect to find if a similar demonstration was performed on the following materials: • Piece of meat • Lump of bacon fat • A solution of salt • A piece of paper Answer: • Piece of meat: You would observe a similar reaction involving the release of carbon dioxide and possibly some charring due to the breakdown of proteins and fats. • Lump of bacon fat: Expect significant charring and release of carbon dioxide and water vapor, as bacon fat is mostly composed of lipids. • A solution of salt: There would be no significant reaction or temperature change, as salt (sodium chloride) does not undergo a chemical reaction under these conditions. • A piece of paper: You would see charring and the release of carbon dioxide and water vapor as the cellulose in the paper breaks down. B. Principles of Molecular Toxicology Introduction The function of biological molecules is highly dependent on environmental factors such as pH, salinity, and temperature. This demonstration clearly shows the fragility of biological molecules when placed in environments that are not conducive to most living organisms. It uses egg albumin as a model for investigating environmental conditions that denature biological molecules. Materials • Overhead projector or videocam attached to LCD • Petri plate or clear flat dish • Egg albumin solution or the liquid egg white from one large egg • Bottle of 5M hydrochloric acid with dropper • Bottle of 5M sodium hydroxide with dropper • Bottle of 26g/100ml water solution of copper sulfate with dropper • Bottle of 10g/100ml sodium hydroxide solution with dropper • Bottle of 70% ethanol with dropper Procedure & Inquiry Questions 1. Introduce the concept of denaturation to the class 2. Place the Petri plate on the overhead or focus on it with the videocam 3. Add egg white to the Petri plate until it forms a 1/2cm uniform coating on the surface of the plate while explaining to the class what you are doing. 4. Ask students to describe the observable characteristics of the egg white 5. Add 2 drops of 5M hydrochloric acid and ask the class to observe what they have seen (the egg white curdles as if it were cooked - denaturation of the proteins). 6. Ask the students what properties of the hydrochloric acid caused the proteins to denature 7. Add 2 drops of 5M sodium hydgroxide and ask the class to observe what they have seen (the egg white curdles as if it were cooked - denaturation of the proteins). 8. Ask the students what properties of the sodium hydroxide caused the proteins to denature 9. Add 2 drops of copper sulfate and ask the class to observe what they have seen (the egg white curdles as if it were cooked - denaturation of the proteins). 10. Ask the students what properties of the copper sulfate caused the proteins to denature 11. Add 2 drops of sodium hydroxide and ask the class to observe what they have seen (the egg white curdles as if it were cooked - denaturation of the proteins). 12. Ask the students what properties of the sodium hydroxide caused the proteins to denature 13. Follow up by summarizing the conformational changes that likely took place to the tertiary structure of the albumin LABORATORY IDEAS Laboratory activities are excellent ways of reinforcing complex biological principles. The following inquiries can be used as the basis of student-designed laboratory activities. A. Water Chemistry: Water Hardness a. Have students measure the hardness of different water samples as an indicator of water quality (water hardness is a measure of calcium or magnesium ions). b. The students should be asked to design an experiment that compares water harness to any measurable properties of water and the usability of water to humans. c. Students should also be directed to look up the chemistry and causes of water hardness. d. Provide students with the following materials to carry out the experiment. i. Rain water and tap water from students’ homes and from around the school. ii. Hard water standard composed of 203 g of Magnesium chloride crystals and 147.0 g calcium chloride crystals dissolved in 1 liter of distilled water iii. Distilled water negative control iv. Hard water test kit v. Thermometers vi. Timers vii. Electric heater with beaker to making boiling water bath viii. Access to a freezer ix. Universal pH paper x. Liquid dish soap xi. Suction cups and a glass surface xii. Grease pencil or permanent marker xiii. Large test tubes xiv. Test tube racks xv. Goggles B. pH of life: a. Have students test the pH of various living substances. b. They should be asked to predict the expected pH values for various living materials. c. The students should be directed to make hypotheses about any variations in pH from their expected predictions. They should also be asked to investigate the reason why certain parts of organisms may vary greatly from a neutral pH. d. Provide students with the following materials to carry out the experiment. i. Universal pH paper ii. Instruments for cutting the animal and plant samples iii. Fresh mushrooms iv. Fresh lemons or grapefruit s v. Potatoes vi. Tomatoes vii. Apples viii. Broccoli ix. Beef or chicken livers x. Imitation crab meat chunks (tuna and other fish muscle wastes) xi. Goggles C. Use of ph and salts in food preservation using the catalase test. a. Explain to students that a chemical produced in health cells called catalase is an indicator or cell metabolism. Then explain that certain metabolic pathways associated with catalase cause the decay of certain foods such as vegetables. b. Demonstrate the catalase test by adding hydrogen peroxide to a fresh section of potato (the test material). Bubbling (or the production of oxygen gas) is an indicator of catalase activity. c. Ask the students to design a controlled experiment that investigates the ability pH and certain salt concentrations to preserve food. d. Students should also be asked what would be the most feasible pH or salt levels that preserve food while also maintaining edibility. e. Provide students with the following materials: i. Potatoes ii. Instruments for cutting the potato samples iii. Petri plate halves or a surface for testing the potatoes for catalase iv. Household hydrogen peroxide v. Droppers vi. pH solutions (tablets are available that when added to water provide a buffered solution at a particular pH) 1. pH 2 2. pH 4 3. pH 6 4. pH 7 5. pH 8 6. pH 10 7. pH 12 vii. Salt solutions (sodium chloride) 1. 0% (distilled water) 2. 0.5 % 3. 1% 4. 3 % (close to sea water) 5. 5% 6. 10% f. The students should first add a drop of the test solutions and let it soak into a small slice of potato. They should then add the catalase to see if catalase activity was hindered or enhanced. LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. Students who have successfully mastered the content of Chapter 2 can apply their knowledge for service learning activities in the following ways: 1. Have students visit a local elementary school to give a presentation on the chemistry of foods. 2. Have students talk to church or civic groups about understanding the chemistry of food labels 3. Have students judge science fairs that focus on projects that investigate the chemistry of biological molecules. 4. Have students tutor middle school or high school biology students studying the molecules of life. ETYMOLOGY OF KEY TERMS ana- up; back (from the Greek an- up) cat- down (from the Greek kata- down) colligative depending upon the number of molecules not the specific type (from the Latin colligatus- tying together) hydro- of, or pertaining to, water (from the Greek hydor- water) ion- an electrically charged atom or group of atoms (from the Greek iongoing) electro- pertaining to or involving electricity (from the Greek electronamber) equi- equal (from the Latin aequus- equal) -gen that which produces (from the Greek genes- born or produced) libri balance (from the Latin libra- balance) lys (lysis) dissolution; breaking (from the Greek lysis- dissolution) neutro- neutral; having no charge or affiliation (from the Latin neuterneither) -pathic feeling; suffering (from the Greek pathos- suffering or feeling) proto- first (from the Greek protos- first) radio- dealing with radiant energy; emitting rays (from the Latin radiusray) solute substance dissolved in a solution (from the Latin solutus, past participle of solvere- to loosen) solvent a substance that dissolves another to form a solution (from the Latin solvent, the stem of solvens, which is the present participle of solvere- to loosen) CHAPTER 3: THE CHEMICAL BUILDING BLOCKS OF LIFE WHERE DOES IT ALL FIT IN? Chapter 3 focuses on the molecular level of hierarchy making up the organization of biological systems. This chapter links the concepts of Chapter 2 with the upcoming information on cell origins and cell structure in Chapters 4 and 5. The scope of information being covered in Chapter 3 sets down the founding for understanding cell metabolism, cell replication, cell structure, genetics, and membrane transport. It is essential to review the concepts of Chapter 2 when discussing the properties of molecules covered in Chapter 3. Chapter 3 is also an important reference for the remaining chapters covered in the text. SYNOPSIS Organic molecules are composed of specific functional groups that confer identity, form, and function. Many of these molecules form long¬-chain polymers of characteristic subunits, constituting the macromolecules upon which life depends. The bonds between subunits are formed by dehydration reactions requiring energy and resulting in the subsequent removal of one molecule of water per bond. The bonds are broken via hydrolysis reactions, releasing energy and requiring the input of water. The four types of macromolecules found within all living organisms are proteins, nucleic acids, lipids, and carbohydrates. Carbohydrates include the monosaccharides, single subunits that serve as energy storage molecules, the two unit disaccharides that are plant transport molecules, and the polysaccharides, molecules hundreds of glucose units long and insoluble as a result of their coils or branches. Cellulose and chitin are important structural carbohydrates because most organisms lack the means to degrade them. The nucleic acids, DNA and RNA, are enormously long chains of nucleotides each composed of a five-carbon sugar, a phosphate group, and one of four nitrogenous bases. Specific nucleotide identity is conferred by the base, which may be a purine or a pyrimidine. The complementarity of the nitrogenous bases allows for efficient replication of each strand and enables DNA to exist as a protected double helix. The structure of DNA and RNA differ in the sugars that constitute their backbones and in the chemical composition of one of their pyrimidine bases. Proteins are a diverse group of macromolecules composed of lengthy chains of amino acid subunits. Each subunit consists of a central carbon attached to four functional groups, three that are constant among all amino acids and a fourth (the R group) that confers identity. Proteins have six levels of organization, all of which ultimately depend, therefore, on the initial amino acid sequence and the identity of each unique R group. Special proteins, chaperonins, act as molecular chaperones to help other proteins fold into their active shape. Denaturation results from changing the environmental conditions surrounding a protein. This adversely affects its biological activity, especially when it is an enzyme. Lipids comprise the third group of macromolecules, unique in that they are completely insoluble in water. The simplest are the fats, which provide ideal long-term energy reserves due to their numerous C—H bonds. Other lipids are important components of biological membranes and have polar ends that orient toward water and nonpolar tails that orient away from it. LEARNING OUTCOMES 3.1 Carbon Provides the Framework of Biological Molecules 1. Define different functional groups based on their chemical properties. 2. Contrast hydrolysis and dehydration reactions. 3.2 Carbohydrates Form Both Structural and Energy-Storing Molecules 1. Distinguish between structural isomers and stereoisomers. 2. Distinguish between monosaccharides and disaccharides. 3. Explain why humans can digest starch but not cellulose, while a cow can digest both. 3.3 Proteins Are the Tools of the Cell 1. List seven essential functions of proteins in the life of a cell. 2. Illustrate how peptide bonds are formed. 3. Describe the four levels of protein structure, and how each is stabilized. 4. Explain the role of motifs and domains in determining protein structure. 5. Describe the role of chaperone proteins in protein folding. 6. Explain how altered environmental conditions lead to denaturation of proteins. 3.4 Nucleic Acids Store and Express Genetic Information 1. Compare and contrast the structures of DNA and RNA. 2. Explain how genetic information is encoded in the structure of DNA. 3. Describe four significant roles RNA plays in the cell’s utilization of information stored in DNA. 4. Describe how adenosine triphosphate stores and releases chemical energy. 3.5 Hydrophobic Lipids Form Fats and Membranes 1. Distinguish between triglycerides that form solid fats and liquid oils. 2. Explain why the lipid bilayer of a biological membrane forms spontaneously. COMMON STUDENT MISCONCEPTIONS There is ample evidence in the educational literature that student misconceptions of information will inhibit the learning of concepts related to the misinformation. The following concepts covered in Chapter 3 are commonly the subject of student misconceptions. This information on “bioliteracy” was collected from faculty and the science education literature. • After a chemical change it is believed that the original substances remain even though they are altered. • The chemistry in biological systems does not follow all the same rules of inorganic chemistry. • Molecules are glued together. • Food molecules are anything useful taken into the body such as water, minerals, and carbon dioxide. • Digestion is the breakdown of molecules that releases usable energy from food. • Students are unsure about the hierarchical order of atoms, molecules and cells. • Carbohydrates serve only as a source of fuel for the body. • All polysaccharides are starches. • All carbohydrate polymers are for food storage. • Proteins are not energy sources for the body. • There are only 20 types of amino acids in nature. • Amino acids and proteins are not related molecules. • Fats produce more energy than carbohydrates. • Fats only serve as a stored source of energy. • Students often confuse amino acids and nucleic acids. • All proteins have tertiary structure. • Proteins are a 100% representation of the DNA information. • Nucleic acids solely serve the purpose of genetic material. • Saturated fats are bad, while unsaturated fats are good. • Cholesterol is bad for the body. • Fats travel as clumps of insoluble material in the blood. • Organic molecules are only produced by organisms. INSTRUCTIONAL STRATEGY PRESENTATION ASSISTANCE The content of this chapter builds upon that of the previous one. The emphasis here is chemistry as it relates to the composition of living organisms. This material is a necessary “evil” to understand most of the remainder of this text, including cellular organization, physiology, energetics, heredity, and (with current molecular trends) even organismal taxonomy. Unfortunately, chemistry is one of the reasons your students may have enrolled in biology, assuming it to be less rigorous than chemistry or physics. Do not assume that your students will inherently understand what you mean when you draw C—H or C = O on the overhead or blackboard. Explain the conventions of biochemistry and define any abbreviations you find useful, including CHO for carbohydrates, AA for amino acids, FA for fatty acids. This is valuable not only from an informational standpoint, but it will improve their note-taking in class. Mnemonics, acronyms, and various word associations may also be helpful to the beginning student. It is easy to remember which molecules are pyrimidines and which are purines if one associates the smaller molecule with the larger name. It is important that your students completely understand the structure of a five carbon sugar molecule. The apex of the pentagon is an oxygen molecule, the four other corners are carbons. The number 4 carbon has the number 5 carbon attached to it. Students may mistakenly interpret the simpler drawings of the phosphodiester bond as having the phosphate attached to the number 4 carbon instead of the number 5 carbon. This will be more important in chapters 13 and 14 when the synthesis of DNA is presented and students must understand what is meant by the 3’ and 5’ ends of the molecule. The hydroxyl placement on the DNA and RNA sugar molecules has a strong bearing on the stability of the linear molecule. RNA has hydroxyls on both the 2 and 3 carbons, therefore the phosphodiester bond can jump between them. DNA has a hydroxyl on only the number 3 carbon, the phosphate can attach only at that location. HIGHER LEVEL ASSESSMENT Higher level assessment measures a student’s ability to use terms and concepts learned from the lecture and the textbook. A complete understanding of biology content provides students with the tools to synthesize new hypotheses and knowledge using the facts they have learned. The following table provides examples of assessing a student’s ability to apply, analyze, synthesize, and evaluate information from Chapter 3. Application • Have students apply the concept isomers to distinguish between molecules that can be beneficial or toxic to the body. • Ask students to explain why a laboratory model of digestion requires water to operate properly. • Ask students to explain why foods high in saturated fats stay fresher than foods high in unsaturated fats. Analysis • Ask students to explain why keeping track of dietary amino acid intake is more important than just knowing that proteins are being taken in the diet. • Ask students to explain what nutrient molecules would be reduced if plants were deprived of fertilizers containing nitrogen and phosphorus. • Have the students explain what would happen to the body of an athlete who does not take in glucose before and after heavy exercise. Synthesis • Ask students to find a commercial application for new types of polymers made from beta forms of carbohydrates. • Ask students to design hypothetical low calorie foods using isomers of carbohydrates. • Ask students to find potential medical uses of amino acids that have R groups that are very different from those commonly used by organisms. Evaluation • Ask students to explain why organisms found on another planet may not be of nutritional value to humans. • Ask students to evaluate the use of chitin as a component of health foods. • Have students compare the benefits and risks of dietary supplements that contain nutrients only in the forms of amino acids, monosaccharides, and fatty acids. VISUAL RESOURCES 1. Use molecular models whenever possible, make sure they are large enough to be seen in the back row. Construct your own from ping pong balls and pencils, or styrofoam balls and straws. Pop-it beads are valuable for describing polymerization of nearly all of the biomolecules, especially amino acids forming polypeptide chains. A coiled telephone cord effectively resembles an alpha helix. 2. Several supply companies sell plastic biomolecule sets made of clinging plastic that are of sufficient size for small to medium size classes. One could construct similar sets from differently shaped or colored acetate pieces for use on an overhead in a very large class setting. 3. Construct your own protein by using 50 pony beads composed of 20 different colored pony beads [to represent the 20 different amino acids] and craft wire [available at local discount stores]. Emphasize the primary structure of amino acids that you constructed. Secondary and tertiary structure can also be demonstrated by bending the strand of beads. IN-CLASS CONCEPTUAL DEMONSTRATIONS A. Principles of Protein Denaturation Introduction Protein shape is an important determine of a protein’s overall function and role in the body. This simple demonstration provides a tangle model of how protein denaturation can affect the utility of proteins. It is helpful to provide students with a background about protein shape and function. In addition, it is important to reinforce the factors, such as pH and temperature, that affect protein conformation. Materials • Pipe cleaners • Overhead projector • Petri plate • Fresh uncooked egg white • Dropper bottle of concentrated hydrochloric acid • Dropper bottle of concentrated sodium hydroxide • Dropper bottle of saturated ammonium sulfate • Dropper bottle of 95% ethanol Procedure & Inquiry 1. Demonstrate the principle of protein folding by twisting pipe cleaner in various shapes representing different types of secondary, tertiary, and quaternary structures. 2. Explain how certain environmental conditions can denature or distort the protein conformation by twisting a representative pipe cleaner protein in another shape. 3. Ask the students to explain how the distorted shapes could affect protein function. 4. Pour the uncooked egg white into a Petri plate and place the plate on an overhead projector. 5. Show the class the uniform consistency of the egg while explaining that it is composed of a solution globular proteins. 6. Add at least three drops of concentrated hydrochloric acid and ask the class to explain their observations of the denaturation. 7. Add at least three drops of concentrated sodium hydroxide. Again observe the denaturation. 8. Add at least three drops of concentrated ammonium sulfate. Again observe the denaturation. 9. Add at least three drops of 90% ethanol. Again observe the denaturation. 10. Explain that the solutions are altering the shapes of the proteins so that they take on a linear shape that polymerizes with nearby proteins. 11. Ask the students to explain how the denaturation of egg white proteins could affect the roles of these proteins. 12. Ask students to hypothesize if the conditions that alter protein shape could also influence the shape of other polymers. 13. Ask students to think about other environmental factors that could alter the final shapes of proteins. 14. Have students link the effects of genetic code alterations to the denaturation cause by environmental conditions. B. Properties of Storage Polymers Introduction This demonstration provides insight into why body structures store polymers instead of single units of molecules. Equal masses of glucose and starch are added to equivalent volumes of colored water to demonstrate the viscosity differences. It can be demonstrated how polymerization reduces the viscosity, and subsequently the osmolarity of molecules stored in solution in cells or extracellular fluids. Materials • 80 grams glucose • 80 grams sucrose • 80 grams starch • 6 400 ml beakers • 3 stirring rods • 600 milliliters of 300C distilled water • Dropper bottle with red food coloring Procedure & Inquiry 1. Place the carbohydrate samples into separate beakers respectively labeled glucose, sucrose, and starch. 2. Add several drops of red food coloring to 600 milliliters of water until the water is dark red. 3. Explain to the class that you have three equal masses of carbohydrates. 4. Ask the class to recall the structural properties of glucose, sucrose, and starch. 5. Tell the class that you will be adding each carbohydrate to equal volumes of water. 6. Add the 200 ml of the water colored distilled water to each beaker of carbohydrate and mix. 7. Then demonstrate to the class the properties of each solution as it is poured into another beaker. 8. Ask the class to comment on the thickness of each solution. 9. Ask the class to discuss how the viscosity of a solution could affect its properties in a living organism. 10. Have the students describe why cells are more likely to store and transport carbohydrates in the form of disaccharides and polysaccharides. 11. Ask students to hypothesize the way organisms can use take advantage of the properties of concentrated solutions of carbohydrates. LABORATORY IDEAS A. Simple DNA Extraction a. Have students do a simple DNA extraction while reinforcing the chemistry of nucleic acids. b. The students should think about the role of each step used to isolate the DNA from the rest of the organism’s chemistry. c. Provide students with the following materials: i. Kiwi fruit or strawberries cut into 1 cm cubes ii. Small self-sealing plastic bags iii. Funnel iv. Beaker that fits funnel v. cheese cloth cut to fit the funnel vi. Ice water bath vii. 20ml aliquots of DNA extraction solution 1. Made by adding 100 ml of clear dish soap to 1 liter of distilled water containing 15 g of table salt and 5 grams of meat tenderizer. viii. Isopropyl alcohol ix. Small test tubes x. Small plastic droppers xi. Wooden toothpicks d. Ask students to carry out the following steps: i. Add 4 pieces of to the plastic bag ii. Add 20 ml of extraction solution to the bag containing the fruit chunks and seal the bag iii. Mush the fruit thoroughly for 3 minutes being careful that the bag does not break iv. Cool the bag in the ice bath for 1 minute v. Repeat the mushing and cooling step at least three times vi. Filter the mixture through the cheesecloth placed over the filter vii. Add approximately 3 ml of mushed fruit solution into a test tube viii. Slowly add approximately 3 ml of Isopropyl alcohol to each tube ix. Ask students to notice the DNA that clumps up and floats to the top of the tube. x. Have students remove the DNA with a toothpick and observe its properties. xi. The sample can be dried and kept indefinitely if stored dry. B. In Search of Proteins a. In this investigation students will hypothesize the presence of detectable levels of protein in different food substances. b. Students should be asked to hypothesize the relative protein content of the foods provided in this activity: grape, beef liver, canola oil, carrot, and potato. This determination should be based on the tissue composition of the organisms from which the food was obtained. c. Provide students with the following materials: i. 1 cm cubes or small samples of grape, beef liver, canola oil, carrot, and potato. ii. Distilled water iii. Test tube rack iv. 6 test tubes v. Buiret solution d. Ask students to carry out the following instructions: i. Label test tubes with the names of the samples and place them in the test tube rack. One tube should be labeled water ii. Place a small amount of each sample into the appropriately labeled test tube. Sample should be about the size of a fingernail iii. Add 5 ml of Biuret solution to each of the test tubes iv. Gently shake each tube for 2 minutes v. Observe the tubes for a purple color change indicating the presence of protein vi. Have students compare their findings to the hypotheses they made earlier vii. They should be encouraged to search the internet to confirm if their findings match the scientific and nutritional literature e. Buiret solution should be disposed as a hazardous waste C. Carbohydrate Search a. In this investigation students will hypothesize the presence of glucose and starch in different types of crops plants b. Students should be asked to hypothesis whether a particular crop plant structure provided in the lab contains glucose and starch: banana, potato, corn, grape, canola oil, carrot, and potato. This determination should be based on the tissue composition of the organisms from which the food was obtained c. Provide students with the following materials: i. Slightly crushed cubes or cut sections of banana, corn, grape, celery, carrot, and potato ii. Test tube rack iii. 12 test tubes iv. Benedict’s - glucose test v. Lugol’s solution or Potassium Iodide (IKI) - starch test vi. Hot water bath d. Instruct students to carry out the following steps: i. Label 2 sets of test tubes with the names of the samples and place them in the test tube rack. ii. Label on set of replicate tubes with “Glucose” and other set with “Starch” iii. Place a small amount of each sample into both of the appropriately labeled sets of test tubes. Sample should be about the size of a fingernail. iv. Add 5 ml of Benedict’s solution to each of the test tubes labeled “Glucose” v. Gently shake each tube for 2 minutes vi. Heat all of the test tubes together in a hot water bath for 5 minutes vii. Observe the tubes for a brick-red color change indicating the presence of glucose viii. Have students compare their findings to the hypotheses they made earlier ix. Add 5 ml of IKI solution to each of the test tubes labeled “Starch” x. Gently shake each tube for 2 minutes xi. Observe the tubes for a dark blue to black color change indicating the presence of glucose xii. Have students compare their findings to the hypotheses they made earlier xiii. They should be encouraged to search the internet to confirm if their findings match the scientific and nutritional literature e. Benedict’s and IKI solution should be disposed as a hazardous waste LEARNING THROUGH SERVICE Service learning is a strategy of teaching, learning and reflective assessment that merges the academic curriculum with meaningful community service. As a teaching methodology, it falls under the category of experiential education. It is a way students can carry out volunteer projects in the community for public agencies, nonprofit agencies, civic groups, charitable organizations, and governmental organizations. It encourages critical thinking and reinforces many of the concepts learned in a course. Students who have successfully mastered the content of Chapter 3 can apply their knowledge for service learning activities in the following ways: 1. Have students visit a local elementary school to give a presentation on understanding the nutrients listed on food labels. 2. Have students talk to young athletes about the importance of carbohydrates and amino acids in the diet. 3. Have students do an educational session on paper disposal. They should use their knowledge of cellulose to explain why paper is a major reason for landfills filling up in the United States and why recycling is an effective way for reusing paper products. 4. Have students tutor middle school or high school biology students studying the molecules of life. ETYMOLOGY OF KEY TERMS enantio- opposite; mirror image (from the Greek enantios- in opposition) -gen that which produces (from the Greek genes- born or produced) glyco- of, or relating to, sugar (from the Greek glykys- sweet) hydro- of, or pertaining to, water (from the Greek hydor- water) iso- equal; same (from the Greek isos- equal) macro- large; large enough to be seen with the naked eye (from the Greek makros- long) peptide compound containing two or more amino acids (modern derivative of peptic and pepsin, which is from the Greek peptikos- conducive to digestion) phobic fear or aversion to (from the Greek phobos- fear or panic) poly- many (from the Greek polys- many) stereo- in three dimensions (from the Greek stereos- solid) Instructor Manual for Understanding Biology Kenneth Mason, George Johnson, Jonathan Losos, Susan Singer 9780073532295, 9781259592416
Download
Close
Close
