Modeling the Chloroplast

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Objective

Students will construct a model to determine the function of a chloroplast during the light reactions.

Big Idea

How does photosynthesis benefit plants? In today's lesson, students how the chloroplast is a energy converting machine.

What Students will Learn in this Lesson

1 minutes

By constructing a classroom size model of the chloroplast, students will trace where oxygen is made and sugar is produced during the photosynthesis reaction. Here is an overview of what students will learn today.

Hook/Check for Understanding

3 minutes

Using the following assessment probe ask students to indicate what plants use as food. This probe will provide insight into students’ understanding of food and plants.

Organisms, including plants, need food to survive.  In your lab notebook under the heading, WHAT PLANTS NEED FOR FOOD,  list the things you think plants use as food.  

  • sunlight
  • plant food from a garden store
  • sugar
  • carbon dioxide
  • minerals
  • fertilizer
  • soil
  • water
  • leaves
  • oxygen
  • chlorophyll
  • vitamins

Explain your thinking.  How did you decide if something on the list is food for plants?

based on Keeley, Page. 2007. Is It Food For Plants? Uncovering Student Ideas in Science: Volume 2. NSTA Press: Arlington, VA.

 

Student Modeling Exercise: The Micromodel

10 minutes

For this activity, students will construct a mini-model of a chloroplast. Provide students with the following materials:

  • paper plates (white or green)
  • hot glue guns/sticks or craft glue
  • scissors
  • printed labels or index cards & markers
  • various green craft materials like sponges, felt, foam sheets, plastic beads, buttons, fuzzy sticks, ribbon, bubble wrap
  • fruit by the foot
  • junior mints

Ask students to research the structure of the chloroplast and build a model that best reflect what scientists think.

Using the provided student handout, students will evaluate the effectiveness of their model.  

Student Modeling Exercise: The Macromodel

20 minutes

Once students have completed the mini-model and have a good understanding of the structure of the chloroplast, they should begin to transform the classroom into a chloroplast. (See attached directions.)

For the model construction, the following equipment and supplies are necessary.

For each lab group

  • 7 Green trash bags
  • Duct tape
  • Clear packing tape
  • Green paper
  • Newspaper for stuffing the trash bags
  • White paper for labels
  • Push pins

Using the student handout, follow the procedure for constructing a granum.  Have students connect their granum with other groups' grana using green paper to represent the thylakoid membrane.  

Once the classroom is a chloroplast, guide students through the photosynthesis reaction. Students will go through the big ideas of the light and dark reactions and their location within the chloroplast. 

After guiding students through the tour, have them complete the RAFT Writing 1 - The Chloroplast.  (Note: “RAFT” writing is a paper written from a viewpoint other than your own as a student, to someone other than your teacher. RAFT stands for Role, Audience, Format, and Topic.)

• You will be writing about the structure of a chloroplast, from the viewpoint of a photon of light that has entered the chloroplast.

• Your audience will be other photons that have not yet entered the chloroplast. 

• The format will be a descriptive trip through the chloroplast, relating what you as a photon “saw” and what happened to you or what you did.

• The paper should be creative and not a copy of source information. Include a title.

• Write it in your own words and be able to describe or explain the information using terminology you’ve learned. 

 

Putting It All Together: A Comparison of the Light and Dark Reactions

15 minutes

Next, have students revisit the assessment probe to which they responded earlier in the period.

Using the information they developed in their model, have students revise their answer using the FACT, I Used to Think...But Now I Know. (Note: See student assessment probe revision.) Students should support their revised thinking with evidence from their model.

Homework:  

“RAFT” writing is a paper written from a viewpoint other than your own as a student, to someone other than your teacher. RAFT stands for Role, Audience, Format, and Topic.

• You will be writing about the structure of a chloroplast from the viewpoint of a water molecule that has entered the chloroplast.

• Your audience will be other water molecules that have not yet entered the chloroplast.

• The format will be a descriptive trip through the chloroplast, relating what you as a water molecule “saw” and what happened to you or what you did.

• The paper should be creative and not a copy of source information. Include a title.

• Write it in your own words and be able to describe or explain the information using terminology you’ve learned.

• Review the process of photosynthesis before you begin.