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.
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Worksheet
portion of
module
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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
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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).
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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.
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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!
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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?
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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?
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Module Developers:
Please contact us if you have comments/suggestions/corrections
Kathleen Hoffman
Department of Mathematics and Statistics
University of Maryland Baltimore County
khoffman@math.umbc.edu
Jeff Leips
Department of Biological Sciences
University of Maryland Baltimore County
leips@umbc.edu
Sarah Leupen
Department of Biological Sciences
University of Maryland Baltimore County
leupen@umbc.edu
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.
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