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ScenarioāMapping Photosynthesis
Scenario: Mapping Photosynthesis
Photosynthesis is arguably the most important biological process on the Earth. All of the energy for the planet can be traced to the sun, but only photosynthetic organisms (plants, algae and some cyanobacteria) can directly utilize this energy. Through highly coordinated metabolic pathways, these photoautotrophic organisms capture solar energy and transform solar energy into the chemical bond energy of carbohydrates and other organic materials, providing usable energy for ecosystems across the planet. As these organisms conduct photosynthesis they also liberate oxygen and consume carbon dioxide, shaping the conditions of the Earthās atmosphere.
Because of the central position of photosynthesis to all life, it is vital that all individualsānot just biologistsāhave an accurate understanding of the process. Thus, it is especially important that biology teachers have an accurate and comprehensive understanding of the events of photosynthesis. In addition to their conventional coursework, many biology departments require special courses for students who are interested in teaching biology. These courses are designed to ensure that they are well- prepared to effectively teach the fundamental concepts in the discipline, like photosynthesis.
One tool that may be used to monitor and assess prospective biology teachersā understanding of key concepts during their course of study is that of concept mapping. Concept mapping is a technique to graphically organize knowledge into a hierarchy of concepts. Within a map, concepts are linked to related concepts by lines, which are labeled with linking words to define their relationships, forming a proposition. Maps are generally hierarchical, with broader concepts at the top, and more specific concepts below. Rich concept maps have cross-links connecting concepts in one branch of the map to concepts in another. Concept maps reveal an individualās knowledge structure and vary by individual. They are useful in identifying misconceptions and gaps in oneās knowledge structure about a particular concept. A concept map of āconcept mappingā illustrates the technique (Figure 1).
ScenarioāMapping Photosynthesis
Figure 1. Concept map of āConcept Mappingā
Consider the concept map of āPhotosynthesisā produced by a student entering the program for biology teachers (Figure 2).
Pre-ActivityāMapping Photosynthesis
Pre-Activity Assignment : Mapping Photosynthesis Name ________________________
Carefully read āMapping Photosynthesisā and answer the following questions.
- In the concept map of photosynthesis, the student links three propositions to form the strand: āPlants conduct photosynthesis instead of respiration which is conducted by animals.ā This statement ______. a. would be accurate if it indicated that plants conduct photorespiration instead of respiration b. is scientifically accurate c. would be accurate and more comprehensive if it accounted for algae & cyanobacteria which are also photosynthetic d. is a misconception, as plants conduct both photosynthesis and respiration e. would be accurate and more comprehensive if it accounted for fungi and bacteria that also are not photosynthetic
- In the concept map of photosynthesis, the student forms and connects the propositions: āPlants conduct photosynthesis to create energy.ā This statement _______. a. is scientifically accurate b. is a misconception, as energy is transformed, not created, during photosynthesis c. is accurate for CAM plants, but not C 4 plants d. is accurate for C 3 plants, but not CAM plants e. would be accurate and more comprehensive if it accounted for algae & cyanobacteria
- Other students indicated in their concept maps that āPhotosynthesis occurs in two sets of reactions referred to as the Light-dependent Reactions and the Calvin cycle.ā If this student were to indicate the products of the light-dependent reactions in her map, the map should include all of the following terms except _______. a. glucose b. ATP c. NADPH d. O 2
- To indicate an accurate understanding of where the oxygen produced during photosynthesis comes from, she should connect the term āoxygenā to the concept of ____________. a. water b. carbon dioxide c. glucose d. NADPH e. chlorophyll
Pre-ActivityāMapping Photosynthesis
- In the next class meeting you will work in small collaborative groups to analyze and evaluate student responses to test questions about photosynthesis.
Each person in the group will act as the āfacilitatorā for one question set, leading the group discussion, promoting input from each of the other students (who will be acting as ādiscussantsā) and formalizing the group response. In the role of a discussant, students provide their knowledge, experience and perspectives, compare and contrast the inputs of other members of the group and collaborate in the formulation of the group response. At the end of the activity, you may be called on to present your groupās answers to one of the question sets (not necessarily the one you were the facilitator for). You will act as both a facilitator and a discussant in the activity.
Download and critically analyze the reading āMapping Photosynthesis.ā Bring the reading with you to the next class meeting.
Group Activity
Question:
- Summarize the events of the Calvin Cycle, highlighting the significance of following molecules in the metabolic pathway:
ļ· Glucose ļ· Ribulose 1,5 bisphosphate (RuBP) ļ· ATP ļ· 3-phosphoglycerate (PG) ļ· NADPH ļ· Glyceraldehyde 3-phosphate (G3P) ļ· CO 2
Student Answer: The Calvin cycle is a complex metabolic pathway that results in the production of glucose (and other sugars). Ribulose 1,5 bisphosphate can be thought of as the starting material. Carbon dioxide is combined (fixed) with RuBP forming a six carbon molecule that is unstable and breaks down into 3-phosphoglycerate (3PG). 3PG molecules are phosphorylated (have energy in the form of phosphate added to them from ATP) and reduced (by NADPH) producing Glyceraldehyde 3-phosphate (G3P) which is phosphorylated (has energy in the form of phosphate added to them from ATP) producing RuBP which is put together to make glucose.
______________________ (Facilitator)
Student Grade (circle one) 1 2 3 4 5
Committeeās Comments:
Group Activity
Question:
- Discuss the products of the light-dependent reactions and the significance of these materials to the production of glucose:
Student Answer: The light-dependent reactions are a complex metabolic pathways in which charged particles (protons and electrons from water) are separated, producing an electro- chemical difference on two sides of a membrane. Electrons are stripped from water molecules and are used to produce the electrochemical difference. In this process, ATP and NADPH and oxygen are produced. The NADPH is cycled back into the light-dependent reactions while the oxygen and ATP enter the Calvin Cycle.
______________________ (Facilitator)
Student Grade (circle one) 1 2 3 4 5
Committeeās Comments:
Instructor Resource Guide
Answers Post-Activity Assignment:
- c
- b
- e
- d
Target ResponsesāCritical Question Set
1. Structure of the chloroplast Ratings will vary: Key comments to look for in groupsā responses: ļ· Response should point out inaccuracies regarding the site of the pathways and naming of structures. The chloroplast contains structures called thylakoids that typically form stacked structures called grana. The light-dependent reactions occur along the thylakoid membrane, while the Calvin cycle occurs in the stroma. 2. Summarize the events of the Calvin cycle Ratings will vary: ļ· Response should point out a few inaccuracies: Note that some G3P molecules are combined to make carbohydrates (glucose), while others are converted into RuBP. 3. Products of the light reactions Ratings will vary ļ· Response should point out that the answer is incomplete, not fully addressing the question, and also contains some inaccuracies. Note that photosystems incorporated into the thylakoid membrane produce NADPH, ATP and O2. The O 2 is released into the atmosphere, while the NADPH and ATP are utilized in the Calvin cycle in the manufacture of carbohydrates.
Photosynthesis
includes is conducted by
Light-dependent 1. _______ Plants Algae Some reactions Cyanobacteria
are are uses uses takes place uses occurs in at
Water Light Energy 2. _______ CO 2 stroma Photoautotrophs
of produces serve as
chloroplast
O 2 3. ____ NADPH Producers
are utilized to produce are vital to
- ________ Ecosystems
Mapping Photosynthesis
An Active-learning Exercise
Objectives
ā¢ During this activity you will:
-Assess and assign a grade to student
descriptions of the events of photosynthesis
(evaluation).
-Justify your assessments of descriptions of
the events of photosynthesis (evaluation).
Activity Guide
ā¢ Work in groups as assigned to discuss and answer
question sets.
ā¢ Different student to act as a facilitator for each question
set.
ā Lead discussion; formalize group response.
ā¢ Each student acts as a discussant for other question sets.
ā Provide insights & perspectives; consider, compare & contrast
inputs of others as you collaborate to form group response.
ā¢ You may be called on to present your groupās answers to
class.
