Putting The Energy Into Photosynthesis

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SWBAT design an an illustrated model to represent the chemical equation of photosynthesis that demonstrates the transformation of light energy into chemical energy.

Big Idea

Keep your students tuned-in when you start to talk in the foreign language of "chemistry". This lesson demystifies photosynthesis by simplifying the complex chemical process into small easy to understand steps!

Video Introduction: Stop The Yawning!

1 minutes

STOP your students' yawning and put the ENERGY into photosynthesis!  This video clip discusses the highlights of this lesson by implementing music and models into our curriculum.

Hook - Energizing Student Interest in Photosynthesis

5 minutes

You may remember the movie, "Billy Madison", where the main character says "Chlorophyll?  Sounds more like bore-aphyll." This is what many of the students are thinking as soon as the concept of photosynthesis makes an appearance in the Biology curriculum.  This negative attitude is usually a response when students get lost among the details of the chemical reaction and lose site of the big picture of the process of photosynthesis. To simplify the process for your students, explain photosynthesis as a chemical reaction that simply absorbs light energy using the green pigment of chlorophyll  to create glucose sugar, or stored chemical energy.  The chemical reaction of photosynthesis is far more complex and detailed, but it is up to you to differentiate the instruction based on the academic abilities of your students.  

This video is a short introduction to present the chemical reaction of photosynthesis to your students:

See . . . photosynthesis can be fun when you incorporate Katie Perry into your opening activity.  Have fun with this video and you can even challenge your students to create their own song or poem as a summative activity or preparation for the unit assessment. The options are limitless, but anytime you can incorporate pop culture to make photosynthesis fun your students are bound to be more interested in the curriculum!

Direct Instruction - Identifying The Energy In Photosynthesis

35 minutes

Now that your students have been awoken with the opening song, it is time to dive into the process of photosynthesis using these lively Lecture Notes.  

Keep in mind that the chemical reaction of photosynthesis is very complex, but this lesson focuses on the inputs and the outputs of both the light reaction and the dark reaction (Calvin Cycle).  The image below summarizes the basic level of understanding for students and will serve as an inspiration for the next section where students need to develop a model that illustrates the process of photosynthesis.

Simplified Photosynthesis Diagram



Independent Practice - Modeling The Energy Of Photosynthesis

10 minutes

Students will use the Lecture Notes  from the previous section as a resource to develop a model that illustrates the light and dark (Calvin Cycle) reactions of photosynthesis.  Students do not need to get bogged down with the details of biochemical steps of each process.  The focus should be placed on the inputs (starting materials) and the outputs (ending materials) for each of the two steps.  Students are also encouraged to follow the transformation of energy as it is absorbed as sunlight (light energy) and is converted into glucose (stored chemical energy) for the plant to use during cellular respiration.  

Common Student Misconceptions:

  • Plants can only undergo photosynthesis and will not experience cellular respiration.  **Plants experience cellular respiration in the mitochondria which will convert the stored glucose into energy to grow and sustain life for the plant.
  • The dark reaction cannot occur in the light.  **The dark reaction (Calvin Cycle) is able occur in the light, but is only called the dark reaction because it is light-independent, meaning the this chemical reaction does not NEED the sunlight to occur. 
  • The chloroplast is the only organelle to undergo chemical reactions.  **All of the plant's organelles are undergoing chemical reactions.  The chloroplast contains chlorophyll that absorb the sun's energy that powers the chemical reaction of photosynthesis.
  • Photosynthesis will occur in a plant no matter what!  **The chemical reaction of photosynthesis need the sunlight and the chlorophyll pigment to start the chemical reaction in the thylakoid membrane.  If there is not sunlight (or artificial UV light) then the process of photosynthesis cannot occur.
  • The Calvin Cycle can occur by itself without the light reaction.  **The Calvin Cycle needs the products of the light reaction to occur,so the light reaction must occur for the Calvin Cycle to proceed.  The light reaction provides the materials to allow the dark reaction (Calvin Cycle) to occur.

Sample of Student Work: Illustrated Models and Narrations

Sample of Student Work: Exemplary Photosynthesis Diagram  - This artifact demonstrates the student's attention to detail while trying to master the intricate chemical processes associated with photosynthesis.  The student's effort will support her learning as she examines the diagram to follow each phase of the process as sunlight is converted to stored chemical energy.

Sample of Student Work: Needs Improvement Photosynthesis Diagram- This artifact displays a student's work that appears to be rushed with very little effort.  The greatest concern is that the illustrated model is difficult to read so the student would have a tough time going back to study the model while trying to prepare for an assessment.  Students do not have to be talented artists to be successful in this assignment, but they do need to have attention to detail and attempt to make their illustrated model as neat as possible in order to support their learning of the content.

Sample of Student Work: Narration for the Process of Photosynthesis:This student's summary narration of photosynthesis demonstrates a basic understanding of the chemical processes of this complicated chemical reaction.  As the unit of study progresses, the additional lessons will strengthen this student's level of comprehension.


Close - 3-2-1 of Photosynthesis' Energy

5 minutes

As a final check for understanding for this lesson, students will complete the following question stems?

  • List three facts you learned about photosynthesis and energy conversion (think light energy and chemical energy)
  • Describe two concepts you found interesting about the process of photosynthesis and energy.
  • List one question that you still have regarding photosynthesis and energy.

Close Activity Student Response 1 - This student's response demonstrates insightful analysis of their understanding of photosynthesis.  Unfortunately, the scanned quality is difficult to read, but her responses were a great example of the depth of reflection that this 3-2-1 strategy was anticipating.

Close Activity Student Response 2 - This student's work shows a reasonable level of self-reflection, but the student did not have time to finish their work.  This sample should be used as a reminder that all students work at a different rate and teachers need to plan their lessons accordingly.

Close Activity - Student Response 3 - This student was short, sweet, and to the point.  Although they claim not to have additional questions regarding photosynthesis, I am sure I could identify a few points of misunderstanding if I met with the student 1:1.  This work sample was used as a reminder that even though out students claim to not have any questions, there is always room for extra review to solidify student understanding!

Students will have 2-3 minutes to record their responses to the prompt and will pair share the 3 facts they have learned and the two concepts that they found interesting.

Student volunteers will share their responses from these partner discussions in a whole-class discussion.

The teacher will ask for volunteers to share their one (or more) questions that still remain regarding photosynthesis and energy.  As time permits, the teacher will respond to these questions in an effort to clarify the concepts before the students leave for the day.

Students will watch the video below and create a summary that explains the process of photosynthesis using basic, "non-science" words.  This strategy encourages students to break down the complex chemical reaction of photosynthesis into easy to understand phrases.  This paragraph will serve as a narration to the illustrated model that was created in the "Independent Practice" section above.  

Teacher Note: The video goes into great scientific detail that goes beyond the expectations of the 9th Grade Biology Class, so it is important to forewarn your students to focus their attention on the main ideas that were discussed in class and not to get confused by the extra details that are shared in the video.