General Chemistry Lab Tutorials at Washington University

<body stylesrc="noframes.html" background="/~edudev/images/whitetex.gif"> <h1 align="center"><MAP NAME="FrontPageMap"><AREA SHAPE="RECT" COORDS="338, 140, 468, 159" HREF="mailto:gfrey@wuchem.wustl.edu"></MAP><a href="_vti_bin/shtml.exe/index.html/map"><img src="images/labtutorials.jpg" alt="Lab Tutorials for General Chemistry at Washington University, St. Louis MO 63130" height="160" ismap usemap="#FrontPageMap" width="480" border="0"></a></h1> <hr> <h2 align="left"><a name="Index">Table of Contents</a></h2> <dl> <dd><dir> <li><a href="#Introduction">Introduction</a></li> <li><a href="#Suggested">Suggested Uses for General-Chemistry-Lab Tutorials</a></li> </dir> </dd> </dl> <dl> <dt><font size="4"><strong>Tutorials Available On-Line: </strong></font></dt> <dd><dir> <li><a href="#Bands">Bands, Bonds, and Doping: How Do LEDs Work?</a></li> </dir> </dd> <dd><dir> <li><a href="#Freshwater">Freshwater Chemistry: Inorganic Reactions in the Water Supply</a></li> </dir> </dd> <dd><dir> <li><a href="#MetalComplex">Hemoglobin and the Heme Group: Metal Complexes in the Blood</a></li> </dir> </dd> <dd><dir> <li><a href="#Ferritin">Ferritin Molecular-Graphics Tutorial</a></li> </dir> </dd> <dd><dir> <li><a href="#Gas">Gas Laws Save Lives: The Chemistry Behind Airbags</a></li> </dir> </dd> <dd><dir> <li><a href="#Vision">I Have Seen the Light: Vision and Light-Induced Molecular Changes</a></li> </dir> </dd> <dd><dir> <li><a href="#Dialysis">Maintaining the Body's Chemistry: Dialysis in the Kidneys</a></li> </dir> </dd> <dd><dir> <li><a href="#Acid">Blood, Sweat, and Buffers: pH Regulation During Exercise</a></li> </dir> </dd> <dd><dir> <li><a href="#Vitamins">Nutrients and Solubility</a></li> </dir> </dd> <dd><dir> <li><a href="#Fridge">Phase Changes and Refrigeration: Thermochemistry of Heat Engines</a></li> </dir> </dd> <dd><dir> <li><a href="#Oxidation">Oxidation-Reduction Reactions in the Body: Cytochromes and the Electron-Transport Chain</a></li> </dir> </dd> <dd><dir> <li><a href="#Carboxypeptidase">Enzyme Kinetics: Carboxypeptidase</a></li> </dir> </dd> <dd><dir> <li><a href="#HIV">Enzyme Kinetics: Drug Strategies to Target HIV</a></li> </dir> </dd> <dd><dir> <li><a href="#HIV">Enzyme Kinetics: Drug Strategies to Target HIV</a></li> <li><a href="#Air">Improving Air Quality with Electric Vehicles</a></li> </dir> </dd> </dl> <dl> <dd><dir> <li><a href="#Ack">Acknowledgements</a></li> </dir> </dd> </dl> <dl> <dd><dir> <li><a href="/index.html">Return to Chemistry Department Homepage</a></li> <li><a href="/educational.html">Return to Educational Development Homepage</a></li> <li><a href="/coursepages.html">Return to Courses Homepage</a></li> <li><a href="http://www.wustl.edu">Return to Washington University Homepage</a></li> </dir> </dd> </dl> <hr> <h2><a name="Introduction">Introduction</a></h2> <p>In General Chemistry, students are exposed to fundamental concepts that have applications in many fields, from biology to engineering technology to understanding day-to-day observations. Often, students in General Chemistry work hard to master these concepts without seeing interesting applications until they take more advanced courses later. We have designed a series of WEB-based graphical tutorials to enable students to explore some of these applications of chemical principles. The purpose of this exploration is twofold: to stimulate students' interest in the course material, and to challenge students to think about the ramifications of chemistry and apply their knowledge to new situations. In addition to the information about how chemical principles relate to other areas, the tutorials include a list of additional links and references for further reading, to serve as a launching point for interested and highly-motivated students to learn more about these subjects. Where appropriate, most of the tutorials also include pdb files that the students can download, to view the molecules interactively with a molecular-viewing package such as RASMOL.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a name="Suggested">Suggested Uses for General-Chemistry-Lab Tutorials</a></h2> <p>At Washington University, we use these tutorials as part of the General-Chemistry laboratory course. For each experiment the students perform in lab, they must also complete a tutorial and turn in answers to the questions in the tutorial. Each tutorial describes an application of one or more concepts presented in the experiment. For example, when students synthesize metal complexes in lab, they read about the metal complex heme in the blood. In each of the tutorial descriptions below, we have indicated the nature of the accompanying experiment in our curriculum.</p> <p>However, these tutorials could be used to augment <strong>any</strong> General-Chemistry curriculum; they are not limited to use with these particular experiments. Because they promote critical thinking about many of the concepts encountered in any General-Chemistry course, instructors could use these tutorials in a variety of different ways. For instance, they could be assigned as extra-credit assignments to complement a related lesson, or students might complete the tutorials outside of class to prepare for a class discussion about the applications of the course material. Some of the questions from the tutorials could be incorporated as challenging test questions. Students might also use these tutorials to generate ideas for research projects. </p> <p>Although the tutorials work well if used in sequence, so that students continually recall knowledge from previous lessons and apply it to new situations, each tutorial is also designed to be able to stand on its own. Occasionally, there are references to earlier tutorials or to the experiments in our curriculum, but these can generally be ignored, or the information could be supplied by the instructor.</p> <p>We would like to hear how others have used our tutorials. If you use these tutorials, please acknowledge Washington University and send comments about how you have used these tutorials to Regina Frey at <a href="mailto:gfrey@wuchem.wustl.edu">gfrey@wuchem.wustl.edu</a>.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="PeriodicProperties/MetalBonding/MetalBonding.html" name="Bands">Bands, Bonds, and Doping: How Do LEDs Work?</a></h2> <p>Authors: Rachel Casiday and Regina Frey </p> <p align="center"><img src="images/Bands.jpg" width="88" height="70"></p> <p>In the first laboratory experiment, which accompanies this tutorial, students explore the periodic properties and classify elements as metals, semimetals, or nonmetals. In one part of the procedure students use LED-containing meters to test the conductivity of elements. In the lab manual, students learn that the conductivity properties of metals occur because valence electrons in metal atoms have a "sea" of empty space in which they can "swim." This picture is useful for understanding how metals have sufficiently mobile charged particles to conduct electricity, but it does not fully explain the differences between metals and other elements. To explain the behavior of metals, semimetals, and nonmetals, we need to understand the bonding of solids in more detail.</p> <p>The tutorial provides explanations, in terms understandable by students with only a little high-school-chemistry background, of the differences in crystal structure, bonding, and band gaps that underlie the observed differences between metals, semimetals, and nonmetals. Semiconductor doping is presented to show how the LEDs used in the experiment work. Because this tutorial is used during the first weeks of general chemistry, the tutorial introduces many concepts that the students will not be expected to fully understand until later. Through exposure to simplified yet accurate explanations at this stage, students are motivated to probe into the chemical and physical bases underlying the phenomena they observe in lab. Later, when students learn about quantum mechanics, they will be rewarded to find that they already know a good deal about some of the applications of this theory, and will be able to refer back to this tutorial with greater understanding.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Water/FreshWater/Water.html" name="Freshwater">Freshwater Chemistry: Inorganic Reactions in the Water Supply</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/Water.jpg" width="76" height="70"></p> <p align="left">The quality of freshwater is important for virtually every aspect of our lives, from drinking to industry to agriculture. It may be surprising to find that freshwater does not consist of pure water, but contains many dissolved ions. Many of these ions have no effect on our use of freshwater, others are essential for agriculture or health, and still others can be quite undesirable for the environment or human freshwater use (<em>e.g.,</em> drinking water). Aqueous species in the water supply may also participate in reactions that generate a precipitate (<em>e.g.,</em> calcium carbonate, which produces mineral deposits on cooking dishes, water pipes, and water boilers). These precipitates can cause damage to appliances and pipes and can result in loss of energy efficiency. Thus, a proper balance of these ions in the freshwater supply must be maintained, for the water to optimally serve both the environment and humans.</p> <p align="left">This tutorial accompanies an experiment in which the students begin to explore the area of chemical reactions. The students systematically classify inorganic aqueous solutions by conducting standard inorganic-reaction tests, which produce precipitate, color changes, or gas evolution. The tutorial consists of two parts. In the first, students learn how acid rain is produced from inorganic reactions in the atmosphere, and reacts with soils and building materials to form soluble products, which wash away. In the second, students learn about water hardness, and how the ions in hard water react to leave the deposits associated with hard water. Ion-exchange columns are described as a way to remove hard-water cations from the water supply.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif"alt="Index" border="0"></a></p> <hr> <h2><a href="Hemoglobin/MetalComplexinBlood.html" name="MetalComplex">Hemoglobin and the Heme Group: Metal Complexes in the Blood</a></h2> <p>Authors: Rachel Casiday, Richard Krathen, and Regina Frey</p> <p align="center"><img src="images/Hemoglobin.jpg" width="79" height="70"></p> <p align="left">The ability of metal ions to coordinate with and then release ligands in some processes, and to oxidize and reduce in other processes makes them ideal for use in biological systems. The most common metal used in the body is iron, and it plays a central role in almost all living cells. For example, iron complexes are used in the transport of oxygen in the blood and tissues.</p> <p align="left">Students are first exposed to metal complexes when they synthesize [Co(NH<sub>3</sub>)<sub>6</sub>]Cl<sub>3</sub> and Cu(NH<sub>3</sub>)<sub>4</sub>SO<sub>4</sub>廈<sub>2</sub>O in lab and then explore ligand-exchange reactions of the Co complex and analyze the results spectrophotometrically. This tutorial explains coordinate-covalent bonding in metal complexes in more detail, and explores how the body uses metal complexes in the protein hemoglobin to transport and release the oxygen ligand. Several related concepts are introduced, such as protein structure, conformational changes in the heme group and the hemoglobin protein when oxygen is bound, and the effect of blood concentrations of CO<sub>2</sub> and H<sup>+</sup> on the binding of O<sub>2</sub> to hemoglobin. Hence, the tutorial illustrates a biological application of the course material, and lays a foundation for future exploration of these concepts in general chemistry and biology courses.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Ferritin/FerritinTutorial.html" name="Ferritin">Ferritin Molecular-Graphics Tutorial</a></h2> <p>Authors: Regina F. Frey, Maureen J. Donlin, and James K. Bashkin (1995)<br> Modified by Rachel Casiday and Regina Frey (1998)</p> <p align="center"><img src="/~edudev/images/ferritin.gif"></p> <p align="left">Iron, an essential element in living organisms, is commonly used in the Fe(II) oxidation state. But in our oxidizing atmosphere, Fe(III) is the more prevalent oxidation state. At the physiological pH of 7, the Fe(III) ion concentration in aqueous solution is minimal. However, most organisms maintain an intracellular concentration of Fe(III) several orders of magnitude higher than simple aqueous solutions permit. This discrepancy in concentration demonstrates the striking ability of biochemical systems to concentrate and store iron. Conversely, iron can be very toxic, so the ability to store and release iron in a controlled fashion is essential. Cells have solved this problem of iron storage by developing ferritins, a family of iron-storage proteins that sequester iron inside a protein coat as a hydrous ferric oxide-phosphate mineral similar in structure to the mineral ferrihydrite.</p> <p align="left">This molecular-graphics tutorial is used in conjunction with the laboratory experiment in which the students learn and apply the principles of absorption spectroscopy, metal chelation, redox reactions, kinetics, and three-dimensional structure-function relationships to study the chemical properties of the iron-storage protein ferritin. The tutorial is used as an introduction to three-dimensional structure and structure-function relationships, and to give the students a better understanding of the iron-release process. It builds on many of the concepts presented in the Hemoglobin tutorial and helps students to visualize the molecules they are using in lab. To facilitate molecular visualization, students are required to use the pdb files for interactive viewing when they complete the assignment for this tutorial. </p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Airbags/airbags.html" name="Gas">Gas Laws Save Lives: The Chemistry Behind Airbags</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/Airbags.jpg" width="60" height="70"></p> <p>The development of airbags began with the idea for a system that would restrain automobile drivers and passengers in an accident, whether or not they were wearing their seat belts. The road from that idea to the airbags we have today has been long, and it has involved many turnabouts in the vision for what airbags should be expected to do. The automobile industry started in the late 1950's to research airbags and soon discovered that there were more difficulties in the development of an airbag than anyone had expected. Crash tests showed that for an airbag to be useful as a protective device, the bag must deploy and inflate within 40 milliseconds. Once a sensor determines that a collision has occurred, an explosive reaction is triggered, generating nitrogen gas (N<sub>2</sub>). This gas fills a nylon or polyamide bag at a velocity of 150 to 250 miles per hour. In order for the airbag to cushion the head and torso with air for maximum protection, the airbag must begin to deflate (<em>i.e.,</em> decrease its internal pressure) by the time the body hits it. Designing an airbag that meets these criteria requires both a macroscopic and a microscopic understanding of the behavior of gases.</p> <p>This tutorial accompanies an experiment on stoichiometry and the ideal-gas law in which oxygen gas is generated via photodecomposition. The chemical reactions that generate the gas used to fill the airbag are described, and students are required to balance them and calculate the amount of starting material required to fill the airbag in 40 ms. Macroscopic (ideal-gas law) and microscopic (kinetic theory of gases) pictures of gas behavior are explained in the context of the inflating airbag. Then, the mechanical principles that allow airbags to protect us in an accident are explained. Finally, students are asked to consider another aspect of airbag chemistry when they read about problems with undetonated-airbag disposal.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Vision/Vision.html" name="Vision">I Have Seen the Light: Vision and Light-Induced Molecular Changes</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/Vision.jpg" width="87" height="70"></p> <p>The fundamental processes underlying vision are the absorption of a photon by the retinal molecule, and the subsequent isomerization from 11-<em>cis-</em>retinal to all-<em>trans</em>-retinal. The vision process provides an interesting example of the rearrangement of electron density that occurs when a molecule absorbs light, and hence of the change in the molecule's properties. Students complete this tutorial in conjunction with an experiment in which they study the optical-absorption properties of conjugated dye molecules and analyze the results using the particle-in-a-box model. A common difficulty for students first encountering quantum theory is visualizing the changes in electron configuration as physical changes occurring in real molecules. This tutorial helps students see how a real molecule, retinal, changes in response to absorption of an electron, and that this change has important consequences, <em>i.e.,</em> vision. The tutorial also emphasizes the relationship between protein structure and function and describes how retinal-containing proteins with different absorption spectra contribute to color vision.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Dialysis/Kidneys.html" name="Dialysis">Maintaining the Body's Chemistry: Dialysis in the Kidneys</a></h2> <p>Authors: Rachel Casiday, Richard Krathen, and Regina Frey</p> <p align="center"><img src="images/Dialysis.jpg" width="84" height="70"></p> <p>Blood contains particles of many different sizes and types, including cells, proteins, dissolved ions, and organic waste products. It is the job of the kidneys to remove the harmful particles from the blood and regulate the blood's ionic concentrations, while keeping the essential particles in the blood. The kidneys meet these challenges through a remarkably elegant system. This tutorial describes how the kidneys use specialized membrane channels and concentration gradients to control the passage of particles between the tubules that ultimately lead to the ureter for excretion, and the circulating blood. Hydrophilic and hydrophobic properties, concentration gradients and diffusion, and membrane structure are emphasized. Artificial kidney dialysis is also discussed. </p> <p>This tutorial accompanies an experiment in which students learn about biological and artificial membranes, concentration gradients and diffusion across a semipermeable membrane, and the solubility properties of hydrophobic, hydrophilic, and amphipathic molecules. In the experiment, students use dialysis to separate chlorophyll from the proteins to which it is attached in plant cells, study the time-course change in a pH gradient, and examine the effect of detergent on oil-water miscibility.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Buffer/Buffer.html" name="Acid">Blood, Sweat, and Buffers: pH Regulation During Exercise</a></h2> <p align="center"><img src="images/Exercise2.gif" width="64" height="70"></p> <p>Many people today are interested in exercise as a way of improving their health and physical abilities. But there is also concern that too much exercise, or exercise that is not appropriate for certain individuals, may actually do more harm than good. Exercise has many short-term (acute) and long-term effects that the body must be capable of handling for the exercise to be beneficial. In particular, exercise initiates chemical changes in the blood which, unless offset by other physiological functions, cause the pH of the blood to drop. If the pH of the body gets too low (below 7.4), a condition known as acidosis results. This can be very serious, because many of the chemical reactions that occur in the body, especially those involving proteins, are pH-dependent.Fortunately, we have buffers in the blood to protect against large changes in pH. </p> <p>This tutorial, which accompanies an acid-base titration experiment, describes in detail the carbonic-acid-bicarbonate buffer that maintains the pH of the blood. In addition, acid-base equilibria, equilibrium constants, and Le Châtelier's Principle are discussed with reference to blood-pH regulation during exercise. For instance, the lungs remove CO<sub>2</sub> from the body, shifting the equilibrium of the buffer system and reducing the amount of acid in the blood. Conversely, the kidneys can shift the equilibrium in the opposite direction by removing bicarbonate ion from the blood. Finally, the tutorial shows how the pH-buffer system relates to processes occurring in the blood that have been discussed in other tutorials, such as diffusion across semipermeable membranes (<a href="#Dialysis">Kidney Dialysis tutorial</a>) and gas exchange (<a href="#MetalComplex">Hemoglobin tutorial</a>).</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Vitamins/vitamins.html" name="Vitamins">Nutrients and Solubility</a></h2> <p>Authors: Rachel Casiday, Richard Krathen, and Regina Frey</p> <p align="center"><img src="images/Vitamins.jpg" width="62" height="70"></p> <p align="left">In order to use the nutrients that we take in when we eat, we must first break the food down into its nutritive components, dissolve these components, and then carry them to the place where they will be used in the body. If the nutrients are not used immediately, they will either be stored for later use, or excreted in the urine. Understanding the solubility of nutrients in the different substances of the body is very important for understanding how they can be used or processed in the body. Scientists have developed several ways to discuss the important concepts of solubility. For salts (ionic solids) that dissociate into ions in water, such as the compounds containing the dietary minerals, a solubility product, K<sub>sp</sub>, is typically given. Vitamins are typically described as soluble in water or in lipids, depending on the functional groups on the molecule. A vitamin's solubility in water or in lipids determines where it can be used, and whether it will be stored in fat cells or excreted from the body if it is not needed for immediate use.</p> <p align="left">This tutorial accompanies an experiment in which students determine the solubility product for Ca(OH)<sub>2</sub> and determine the effect of OH<sup>-</sup> concentration on solubility of this compound (common-ion effect). Students learn about the thermodynamics and structural properties of a molecule that make it soluble or insoluble in a given solvent (<em>e.g.,</em> water or fat). A table of vitamin structures allows students to examine the two-dimensional (ChemDraw) and three-dimensional (CPK) structures of seven vitamins. Students can also download and view the three-dimensional structures interactively using a molecular-viewing package such as RASMOL. Olestra, the new fake fat in some snack foods, is discussed because it interferes with the body's absorption of fat-soluble vitamins. The solubility of minerals is explained quantitatively, using the concepts of equilibria and the solubility product (K<sub>sp</sub>). The role of calcium in the body, equilibria involving blood calcium concentration, and the solubility of calcium supplements, are discussed in detail.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Thermochem/Fridge.html" name="Fridge">Phase Changes and Refrigeration: Thermochemistry of Heat Engines</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/Heat.jpg" width="97" height="70"></p> <p align="left">One of the most important practical applications of the principles of thermodynamics is the heat engine. In the heat engine, heat is absorbed from a "working substance" at high temperature and partially converted to work. A refrigerator can be thought of as a heat engine in reverse. The cooling effect in a refrigerator is achieved by a cycle of condensation and vaporization of the nontoxic compound CCl<sub>2</sub>F<sub>2</sub> (Freon). In order to understand how refrigerators work, some knowledge of phase transitions is essential. This tutorial provides both a molecular and a thermodynamic understanding of phase transitions. The refrigeration cycle, which involves phase transitions of Freon and transfers heat from the inside to the outside of the refrigerator, is described in detail. The questions in this tutorial require students to apply Hess's law to phase transitions, and to think about the molecular properties that would allow a substance to be a good refrigerant.</p> <p align="left">This tutorial accompanies a thermochemistry experiment in which students measure the heat change of chemical reactions and use Hess's law to determine enthalpies of formation.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a name="Oxidation">Oxidation-Reduction Reactions in the Body: Cytochromes and the Electron-Transport Chain</a></h2> <p>This tutorial accompanies an experiment entitled "Oxidation-Reduction Reactions: Iron plus Dichromate"</p> <p>This tutorial is currently under development.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="Carboxypeptidase/carboxypeptidase.html" name="Carboxypeptidase">Enzyme Kinetics: Carboxypeptidase</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/Cpepase.jpg" width="67" height="70"></p> <p align="left">The rate of many biological reactions is increased by enzymes, which are proteins that act as catalysts for specific reactions. For an enzyme to exert its effect on a substrate, the substrate must enter the active site of the enzyme to form the enzyme-substrate complex. In the <strong>lock-and-key model</strong>, the amino acids that make up an enzyme's active site in the unbound state are said to form a shape that exactly matches the shape of the substrate. This model is quite useful for visualizing how the enzyme-substrate complex is formed as a crucial step in catalyzing biological reactions. However, the active sites of many enzymes do not have a shape in the unbound form that exactly matches the shape of the substrate. The shape of the active site changes when the substrate binds to the enzyme, creating a shape into which the substrate fits. This concept, known as the <strong>induced-fit model</strong>, is typically used to describe the substrate-binding behavior of many different enzymes. In the human body, carboxypeptidase helps break down proteins, such as those from food, so that their constituent amino acids can be used to synthesize new proteins for the body. Carboxypeptidase is best described by the induced-fit model, because the shape of the active site changes when it binds to a substrate protein.</p> <p align="left">This tutorial accompanies an experiment on chemical kinetics in which students determine the rate law for a reaction and then study the effect of temperature and a catalyst on the rate. In this tutorial students learn that large molecules (<em>e.g., </em>proteins) can also act as catalysts and begin to learn that the shape of a molecule is crucial in determining its ability to increase the rate of a reaction.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="HIV/DrugStrategies.html" name="HIV">Enzyme Kinetics: Drug Strategies to Target HIV</a></h2> <p>Authors: Rachel Casiday and Regina Frey</p> <p align="center"><img src="images/HIV.jpg" width="48" height="70"></p> <p> <p align="left">HIV, the virus that causes AIDS, is one of the hottest areas of medical research today. Recent advances in treating patients with HIV and AIDS, as well as hope for a future cure and vaccine for the deadly virus, center around our understanding of the HIV-infection mechanism. HIV enters the cells of our immune system, replicates its genetic information, and produces new copies of itself, killing the host cells and infecting new ones. HIV requires certain enzymes to catalyze the reactions involved in infecting the body. Hence, if these enzymes could be turned off, then HIV would be unable to reproduce itself and continue an infection. Drugs given to HIV patients inhibit these enzymes, especially reverse transcriptase and HIV protease.</p> <p>This tutorial also accompanies the chemical-kinetics experiment and is designed to accompany the <a href="#Carboxypeptidase">Carboxypeptidase</a> tutorial. Students learn that catalysis is not as simple as it might at first seem, but that the catalyst itself can be inhibited in a number of different ways. Drugs that students have heard about in the media, such as AZT and protease inhibitors, work by blocking the catalytic action of certain enzymes.</p> <p> <a href="#Index"><img src="/~edudev/images/IndexButton.gif" alt="Index" border="0"></a></p> <hr> <h2><a href="AirQuality/AirQuality.html" name="AirQuality">Improving Air Quality with Electric Vehicles</a></h2> <p>Authors: Carolyn Herman and Regina Frey</p> <p align="center"><img src="images/ozonemov.jpg" width="48" height="70"></p> <p> <p>Good air quality is a major factor in public health. Photochemical smog is the most common air-quality problem. This tutorial describes the harmful components of air pollution, the important sources of air pollution in the United States, and several strategies for reducing air pollution. Redox reactions are the basis for understanding each of these topics. For example, one of the major components of air pollution is ozone, and it is the oxidative ability of ozone that causes the harmful effects. The tutorial discusses the oxidative ability of ozone in the body.</p> <p>Automotive emissions increase the ozone concentration even though ozone is not directly produced by these emissions. A simplified mechanism is presented for the production of ozone, and hence the students are introduced to mechanistic chemistry. Current strategies for reducing emissions are discussed, which lead to a discussion of the development of zero-emissions vehicles (ZEV). The current ZEV are electric vehicles and their feasibility is dependent on battery technology, where energy is produced by an oxidation-reduction reaction. The electrochemical cell is the foundation of all batteries. Most electric vehicles use the lead-acid battery (which is the conventional car battery), but there are a number of drawbacks to this battery, namely the weight and the recharging time. Hence, battery technology is an active area of research. This tutorial describes one interesting new design, namely a vanadium-flow battery in which the redox reaction involves solutions instead of solid material. A current is produced through electron transfer from the vanadium (II)ions in solution on one side of the battery to the vanadium (V) ions on the other side. This design looks promising, but it is in its infancy. Thus this tutorial shows that to understand air pollution, its effects, and how to reduce air pollution, one must understand electrochemistry, redox reactions, and the connection between chemical and electrical energy.</p> <p>At Washington University in St. Louis, this tutorial accompanies a second-semester experiment, "Electrochemistry: Cells and Redox Reactions." In this experiment, students learn how to construct an electrochemical cell and how cell potential depends upon the concentrations of the reacting species in the cell. The tutorial expands upon these concepts. Electrochemical methods and redox reactions are discussed from the perspective of air quality, its impact on human health, and the role of battery technologies in addressing air-quality problems.</p> <p>This tutorial and the associated electrochemistry experiment nicely complement the "Energy for the Body: Oxidative Phosphorylation" tutorial and its associated experiment "Redox Reactions: Iron Plus Dichromate.</p> <hr> <h3><a name="Ack">Acknowledgements:</a></h3> <p>The development of these tutorials was supported by a grant from the Howard Hughes Medical Institute through the Undergraduate Biological Sciences Education program, Grant HHMI#71195-502005 to Washington University.</p> <h5>Copyright 1999, Washington University, All Rights Reserved.</h5> <hr> <p><a href="/index.html"><img src="images/accesstert1.JPG" alt="WU Chemistry Homepage" align="left" border="0" hspace="0" width="211" height="99"></a> <nobr> <a href="/educational.html"><img src="images/accesstert2.JPG" alt="Resources Page" align="left" border="0" hspace="0" width="90" height="99"></a> <nobr> <a href="http://www.wustl.edu"><img src="images/accesstert3.JPG" alt="Washington University Homepage" border="0" width="200" height="99"></a><a href="http://www.wustl.edu" name="WashU"> </a><a href="http://www.wustl.edu"></nobr></a> </p>  </body>