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TOPIC: Photosynthesis TUTOR GUIDE MODULE CONTENT: This module contains exercises designed to help students see photosynthesis in both a real-world context and as conceptually integrated with cellular respiration as well as with industrial CO2 production. The module is designed to be implemented in a 50 minute laboratory session. TABLE OF CONTENTS Alignment to HHMI Competencies for Entering Medical Students………………...........1 Outline of concepts covered, module activities, and implementation……..……............2 Module: Worksheet for completion in class................................................................3-6 Pre-laboratory Exercises......................…………..……………………….………….........7 Guidelines for Implementation……………………………...............….............................8 Assessment Questions…………………………………………………………………........8 Contact Information for Module Developers..................................................................9 Alignment to HHMI Competencies for Entering Medical Students: Competency E1. Apply quantitative reasoning and appropriate mathematics to describe or explain phenomena in the natural world. E5. Demonstrate knowledge of how biomolecules contribute to the structure and function of cells. Learning Objective E1.1. Demonstrate quantitative numeracy and facility with the language of mathematics Activity All activities in worksheet E1.6. Apply algorithmic approaches and principles of logic to problem solving E5.2. Demonstrate knowledge of the principles of chemical thermodynamics that drive biological processes in the context of space and time: enzyme-catalyzed reactions… and the chemical logic of sequential reaction steps 2a. - d. 3 Worksheet portion of module 1 Mathematical Concepts covered: - unit conversion - setting up equations - scientific notation - simple manipulations based on the stoichiometry of chemical equations In class activities: - group discussion of answers to pre-class unit conversion problems - setting up of equations based on the stoichiometry of chemical equations - solving these equations Components of module: - preparatory assignment to complete and turn in as homework before class - in class worksheet: - suggested assessment questions - guidelines for implementation Estimated time to complete in class worksheet - 60 minutes Targeted students: - first year-biology majors in introductory biology course covering cell and molecular biology Quantitative Skills Required: - Basic arithmetic - Logical reasoning - Unit conversion 2 Worksheet: Photosynthesis All energy on earth comes from the sun (with the exception of fabulous hydrothermal vent communities on the ocean floor, which are energized by the heat from the earth’s molten core). From that point on, the energy can only be converted to different forms, or be lost as heat. As you know, plants convert light energy to glucose (sugar)-- photosynthesis-- and then either the plants themselves, or the animals that eat them, can use that glucose to produce ATP to do work --cellular respiration. As a reminder, here are the basic chemical equations of photosynthesis and cellular respiration—note how beautifully symmetrical they are! Photosynthesis: 6CO2 + 6H2O + light energy C6H12O6 (glucose) + 6O2 Cellular Respiration: C6H12O6 (glucose) + 6O2 6CO2 + 6H2O + ~36 ATP In your groups, complete the following exercises. 1. Based on the stoichiometry of the equation, how many molecules of CO 2 must enter photosynthesis in order for the plant to produce one molecule of a starch (a chain of sugars) containing 24 carbon atoms? 2. Pisum sativum (pea plant) has a maximum rate of photosynthesis at 25o C. The rate at this temperature is 1 mg glucose per cm2 per hour. a. How much glucose can be theoretically made during an 18 hour lighted period by a single leaf that has a surface area of 20 cm2? b. Given that the molecular weight of glucose is 180 grams, how many moles of glucose is this? c. If a cow eats 40 leaves from the above plant (assuming all leaves have the same surface area and the glucose currently in the leaves is the net glucose production from the last 18 hours), how many molecules of ATP will the animal produce after complete oxidation? (Avogadro’s number = 6.023 x 1023 molecules/mole). 3 d. With the ATP from those 40 leaves, how far could the cow walk? Assume each step the cow takes a) moves it 0.5 meter and b) costs it 4 kilojoules (kJ) of energy. There are 46 kJ of energy per mole of ATP. 3. The 24 power plants in Baltimore metro area collectively emit about 40,300 metric tons of CO2 per day (www.carma.org). To counter this, environmentalists plan to plant trees in the area. a. If on average 500 moles of glucose is synthesized per tree per day, how many trees need to be planted to reabsorb all the CO2 released into the atmosphere every day by the factory? (1 metric ton =1000kg; and the molecular weight of CO2 is 44g/mole) b. If a tree on average occupies 6 x 10-5 sq miles, what percent of the area of Baltimore city needs to be forested to counter the CO2 emitted from power plants alone? The total area of Baltimore city is 92 square miles. 4 MODULE FEEDBACK - Each year we work to improve the modules in the active learning "discussion" sections. Please answer the following question with regard to this module on this sheet and turn in your answer to the TA. You can do this anonymously if you like by turning in this sheet separately from your module answers. How helpful was this module in helping you understand a fundamental concept in photosynthesis? A = Extremely helpful B= Very helpful C= Moderately helpful D= A little bit helpful E = Not helpful at all Module Rating ____________ Thank you! 5 Pre-laboratory Exercises: To be completed before you come to class and handed in at the beginning of class. This homework is designed to review unit conversions, to prepare you for the upcoming module on photosynthesis. Measurements are given in units. For instance, distance is measured in feet, inches, meters, etc, mass is measured in grams, and time is measured in seconds, minutes, or hours. Frequently we would like to convert between different units of measurement, and sometimes units can help us determine if our answer is correct! Here are some facts that you might find useful in the following problems: 5280 feet = 1 mile 3.3 feet = 1 meter 1 inch = 2.54 centimeters 100 centimeters = 1 meter 1. Here is an example on why units may be helpful. Suppose a car is driving 55 miles per hour. How many meters per second is that? 2. How many inches are in a length of rope ½ meter long? 3. If a car travels 45 miles per hour for 3 hours, how many feet has it travelled? 4. If a car travelled 45 miles per hour and went 100 miles, how long did it take? 5. Consider a square that is 1 foot by 1 foot. How many square meters is that? 6 Guide for Implementation: Lab Activity These are pencil and paper activities so no special materials / computers are needed. Have students break up into groups of 3 to work on the problems. After a few minutes or when most teams are done, the TA should then pick a person from 3 groups chosen at random to share with the class their group’s answer to the question. Tell them that everyone in the group should be prepared to share the answer with the class, as you will chose who speaks randomly among the group. Or, have groups do the whole worksheet and debrief afterwards. Assessment Questions Suggested Assessment Questions: Competency E1. Apply quantitative reasoning and appropriate mathematics to describe or explain phenomena in the natural world. Learning Objective E1.1. Demonstrate quantitative numeracy and facility with the language of mathematics Activity 2a. - d. E1.6. Apply algorithmic approaches and principles of logic to problem solving 2a. - d. Suggested Summative Assessment Questions 1. A simple unit conversion as in the homework; could be multiple choice. 2. If a cow gets 0.08 moles of glucose from eating 40 leaves, how many molecules of Na+ could it pump out of its cells using the sodium-potassium pump, assuming for every 2 molecules of ATP bound, 3 molecules of Na+ get pumped across the cell membrane? (Avogadro’s number = 6.023 x 1023 molecules/mole). 3. If a cow gets 0.08 moles of glucose from eating 40 leaves, how many calories has it eaten? Carbohydrates have 4 calories per gram and the molecular weight of glucose is 180 grams/mole. 4. We saw in the module that the cow produces 132.48 kJ of energy from those leaves. Given that each calorie is 4.2 kJ and a calorie is the amount of energy that it takes to raise 1 cm2 of water by 1 degree Celsius, how much volume of cow (cm3) could be heated (raised by 1 degree Celsius) by those 40 leaves? 7 Module Developers: Please contact us if you have comments/suggestions/corrections Kathleen Hoffman Department of Mathematics and Statistics University of Maryland Baltimore County [email protected] Jeff Leips Department of Biological Sciences University of Maryland Baltimore County [email protected] Sarah Leupen Department of Biological Sciences University of Maryland Baltimore County [email protected] Acknowledgments: This module was developed as part of the National Experiment in Undergraduate Science Education (NEXUS) through Grant No. 52007126 to the University of Maryland, Baltimore County (UMBC) from the Howard Hughes Medical Institute. 8