CO Lesson 2 CARBON MONOXIDE: LESSON TWO What are the Health Effects from Exposure to Carbon Monoxide? LESSON SUMMARY Carbon monoxide (CO) is an odorless, tasteless, colorless and nonirritating Grade Level: 9 – 12 gas that is impossible to detect by an exposed person. CO is produced by the Subject(s) Addressed: incomplete combustion of carbon-based fuels, including gas, wood, oil and Science, Biology coal. Exposure to CO is the leading cause of fatal poisonings in the United Class Time: 1 Period States and many other countries. When inhaled, CO is readily absorbed from the lungs into the bloodstream, where it binds tightly to hemoglobin in the Inquiry Category: Guided place of oxygen. CORE UNDERSTANDING/OBJECTIVES By the end of this lesson, students will have a basic understanding of the physiological mechanisms underlying CO toxicity. For specific learning and standards addressed, please see pages 30 and 31. MATERIALS INCORPORATION OF TECHNOLOGY Computer and/or projector with video capabilities INDIAN EDUCATION FOR ALL Fires utilizing carbon-based fuels, such as wood, produce carbon monoxide as a dangerous byproduct when the combustion is incomplete. Fire was important for the survival of early Native American tribes. The traditional teepees were well designed with sophisticated airflow patterns, enabling fires to be contained within the shelter while minimizing carbon monoxide exposure. However, fire was used for purposes other than just heat and cooking. According to the historian Henry Lewis, Native Americans used fire to aid in hunting, crop management, insect collection, warfare and many other activities. Today, fire is used to heat rocks used in sweat lodges. Use of fire in these enclosed spaces can pose a risk of CO poisoning.1 ENGAGE Project an image of the human circulatory system (An example image is shown in the page 2 sidebar). Distribute 3 x 5 index cards or have students take out a half sheet of paper. Have students number 1 through 6 on one side of the card or paper. Ask students the following questions and instruct them to record their answers: 1) What color is oxygenated blood? 2) What makes oxygenated blood this color? 3) What color is deoxygenated blood? 4) What makes deoxygenated blood this color? 5) What is the color of blood in arteries? 6) What is the color of blood in veins? When students are finished recording their answers, the teacher may collect the cards/paper and tally the responses on the board. Discuss responses to gauge student ideas and misconceptions but do not give value to their answers at this point. Let students know that you will revisit these questions at the end of the lesson. 1 CO Lesson 2 VOCABULARY Copies of blank student vocabulary banks (see page 5) can be distributed for completion as either a classroom or homework assignment. EXPLORE Carbon monoxide exposure is one of the leading causes of accidental death due to poisoning in the U.S. The toxic effects of carbon monoxide are primarily caused by the formation of carboxyhemoglobin within the red blood cells. When CO and hemoglobin bind to form carboxyhemoglobin, the oxygen-carrying capacity of the blood is reduced resulting in hypoxia of the tissues. In the presence of carbon monoxide, the affinity of hemoglobin for oxygen is reduced—compounding the effects of carboxyhemoglobin formation. Additionally, carbon monoxide exposure causes immunological and inflammatory changes increasing the adverse effects observed in the victim. Have students watch the short video (http://bit.ly/1Z7Zv2J) showing the effects carbon dioxide, oxygen, and carbon monoxide have on the blood. The teacher can "Blutkreislauf". Licensed under Creative Commons distribute “Lab 1: What Are the Effects of Different Gases on the Color of Blood?” Attribution-Share Alike 2.5 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Blutkreisla (see pages 7-10) for students to complete during the video. uf.png#mediaviewer/File:Blutkreislauf.png *Note: There will be prompts throughout the video for the teacher to pause the video, allowing time for students to record their observations and answers. EXPLAIN Subsequent to watching the video, have students break into small groups and discuss possible explanations for their observations during the video. Then come back together for a whole group discussion on possible explanations from each group accounting for the differences in the color changes of the blood. ELABORATE After completing the other activities, revisit the six engage questions from the beginning of the lesson and discuss the differences between oxygenated and deoxygenated blood and how the normal respiratory cycle of the body is disrupted by exposure to carbon monoxide. 1) What Color is oxygenated blood? Oxygenated blood is bright red. 2) What makes oxygenated blood this Color? Red blood cells contain an iron- containing protein (metalloprotein) called hemoglobin that is primarily responsible for the color of blood. Each hemoglobin molecules has four heme groups and the interaction of these groups with compounds, such as oxygen, determine the color of the blood. When the heme groups combine with oxygen (i.e., blood is oxygenated), a bright red color is exhibited. 3) What Color is deoxygenated blood? Deoxygenated blood is dark red. 2 CO Lesson 2 4) What makes deoxygenated blood this Color? The teacher may guide students to think about where a phlebotomist draws blood from (i.e., veins) and have them explain the color of the blood when it is drawn. Similar to oxygen, carbon dioxide is responsible for the dark red color exhibited by the heme groups contained in the hemoglobin molecules. Carbaminohemoglobin has a blue hue to it, resulting in a For further explanation darker red color of venous blood compared to arterial blood. of O2/CO2 transport in the blood, show students 5) What is the Color of blood in arteries? Arterial blood, or oxygenated blood, is the following video bright red in color (see #3 above). (“Hemoglobin moves O2 and CO2”) from khan 6) What is the Color of blood in veins? Venous blood, or deoxygenated blood is Academy: dark red in color. Veins close to the surface of the skin appear blue because of the http://bit.ly/1nJxmha light scattering properties of the skin, not the color of venous blood. End the discussion by addressing the differences in the binding of carbon monoxide versus oxygen to hemoglobin and why this is an important human health subject. Note that while hemoglobin easily exchanges oxygen for carbon dioxide— as observed by the changes in the color of blood—carbon monoxide binds much tighter and prevents the hemoglobin molecule from subsequently binding to oxygen. Additionally, the follow discussion topics may be used to deepen learning: • What are the similarities and/or differences between carbon monoxide exposure and sickle-cell anemia? • What are the pros/cons of the meat packing industry’s current use of carbon monoxide to preserve the bright red color of meat? • Are some individuals more or less susceptible to the effects of carbon monoxide poisoning (i.e. smokers versus nonsmokers, elderly, children, etc.)? • Why do you think it is important for health professionals to understand chemistry? • Why do sketches of the circulatory system often depict blood as either red or blue? • How might an individual be exposed to carbon monoxide around their home and how can these exposures be prevented? EVALUATE Use the discussions as an opportunity for informal assessment. The lab worksheet provides opportunity for formal assessment. For additional formal assessment, distribute “Comprehension 1: What are the Health Effects of Carbon Monoxide?” and the accompanying guiding questions (pages 15-21). Have students complete this as homework. Notes: 3 CO Lesson 2 Carbon Monoxide Health Effects – Vocabulary Ligand: Cooperative Binding: Hemoglobin: Oxygen: Carbon Dioxide: Oxyhemoglobin: Carboxyhemoglobin: Pulmonary Respiration: Hypoxia: ChemiCal Affinity: SiCkle-cell Anemia: Mendelian GenetiCs: 4 CO Lesson 2 Carbon Monoxide Health Effects – Vocabulary Ligand: A ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. In biology, ligands include substrates, inhibitors, activators, and neurotransmitters. Cooperative Binding: (biochemistry) A type of chemical binding in which a macromolecule’s affinity for its ligand changes with the amount of ligand already bound. Hemoglobin: An iron containing protein in red blood cells that transports oxygen. Oxygen: A colorless, odorless, combustible gas that is the life-supporting component of air. Carbon Dioxide: A naturally occurring chemical compound composed of two oxygen atoms each covalently double bonded to a single carbon atom. It is a colorless, odorless, incombustible gas that is present in the atmosphere and formed during respiration. Oxyhemoglobin: A compound formed when oxygen binds with the heme groups of a hemoglobin molecule. Carboxyhemoglobin: A stable complex that forms from carbon monoxide and the hemoglobin in red blood cells when carbon monoxide is inhaled or produced in normal metabolism. Formation of large quantities can hinder delivery of oxygen to the body. Pulmonary Respiration: The transport of oxygen from the outside air to the cells within tissues and the transport of carbon dioxide in the opposite direction. Hypoxia: A condition in which the oxygen supply to a tissue falls below physiologically necessary levels despite adequate perfusion of the tissue by blood. ChemiCal Affinity: An attractive force between two substances that causes them to chemically combine. SiCkle-cell Anemia: A genetic disorder in which the body makes abnormal hemoglobin causing the red blood cells to form a sickle-shape rather than the normal disk-like shape. Mendelian GenetiCs: The basic laws of inheritance as described by Gregor Mendel, a nineteenth-century Austrian monk who conducted hybridization experiments using garden peas. 5 CO Lesson 2 LAB 1: WHAT ARE THE EFFECTS OF DIFFERENT GASES ON THE COLOR OF BLOOD? Question: What is the importance of an experimental control? Make some observations: Describe any differences between the control sample and the sample treated with O2 (tube #1).