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Sweet Beets: Making Sugar Out of Thin Air


Sarah R. Sletten
Department of Biomedical Sciences
UND School of Medicine and Health Sciences


This directed case study introduces students to photosynthesis and illustrates how biology plays a vital role in the carbon cycle and the conversion of energy. Set in North Dakota along the Red River of the North, the case uses the sugar beet (Beta vulgaris) as a model organism for learning about the process of photosynthesis. The case begins by introducing the sugar beet growing season and the plant's anatomy. Students are provided information specific to photosynthesis in sugar beets and are then asked to explore the process in general. Atmospheric carbon dioxide levels are provided, and after comparing levels between sugar beet growing seasons, students should come to realize that sugars are made from the carbon found in atmospheric carbon dioxide. The case is designed for use in a "flipped" classroom, where students prepare in advance by viewing a number of videos, including one created by the author of the case.  Quiz sheets for the recommended videos are included in the teaching notes.


  • Describe the functions of the leaves and roots of the sugar beet plant.
  • Illustrate the basic process of photosynthesis.
  • Construct and interpret graphs of carbon dioxide concentrations and relate them to growing seasons.
  • Conclude that sucrose is made from carbon dioxide through the process of photosynthesis.


Photosynthesis; carbon fixation; Calvin cycle; carbon cycle; chloroplast; sugar beet; agriculture; Beta vulgaris; Red River

Topical Areas


Educational Level

High school, Undergraduate lower division



Type / Methods

Analysis (Issues), Directed, Flipped



Subject Headings

Agriculture  |   Biology (General)  |   Environmental Science  |  

Date Posted


Teaching Notes

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Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Answer Key

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The following video(s) are recommended for use in association with this case study.

  • Sweet Beets
    This video provides footage from an actual sugar beet field and the beet stockpiles that will make the case more relatable. There is also a basic introduction to photosynthesis in the video that will help prepare students for Part IV of the case study. Created by Sarah R. Sletten for the National Center for Case Study Teaching in Science, 2015. Running time: 4:01 min.
  • Photosynthesis: Fun in the Sun
    Got oxygen? Got food? Well, then you've got to have photosynthesis! This video breaks down photosynthesis into the “photo” part (capturing light energy and storing it) and the “synthesis” part (fixing carbon into carbohydrates). Created by The Penguin Prof, 2012. Running time: 14:36 min.
  • Photosynthesis
    This video explains the process of photosynthesis by which plants and algae can convert carbon dioxide into useable sugar. It begins with a brief description of the chloroplast. It describes the major pigments in a plant (like chlorophyll a and b). It then describes both the light reaction and the Calvin cycle. It finishes with a discussion of photorespiration and strategies for avoiding this problem evolved in CAM and C4 plants. Created by Paul Andersen/Bozeman Science, 2012. Running time: 12:26 min.
  • Photosynthesis: Crash Course Biology #8
    This video explains the extremely complex series of reactions whereby plants feed themselves on sunlight, carbon dioxide and water, and also create some byproducts we’re pretty fond of as well. Created by Crash Course, 2012. Running time: 13:14 min.


Nevada State College
Henderson, NV
Really great case study and perfect timing. I was on the search for a new method to teach photosynthesis. I have a three-hour class period so we watched the videos in class and then proceeded with the case study and blank diagrams of photosynthesis. The students enjoyed it and I liked that it reinforced the steps over and over again in different ways.

Elizabeth Cowles
Eastern Connecticut State University
Willimantic, CT
I enjoyed the case very much. Would you please change the terms "light independent" and "light dependent" please? They are no longer used and are misleading. Current text use "light reactions" and the "Calvin-Benson cycle." Thank you!

Sarah R. Sletten
Division of Science and Mathematics
Mayville State University
Mayville, ND
Author Reply: Thank you for taking interest in this case study and for providing your feedback. The texts that I use as resources for my biology courses mainly use “light reactions” and “Calvin cycle” for the bulk of the content as well. However, there is a distinction between the reactions that require light energy and those that do not and many resources identify that distinction. The case does state that the Calvin cycle are the set of the reactions that do not need light energy to proceed. I suggest that instructors use the terminology that is consistent with the texts and other resources for their courses.

Denise Stoeckel
Biology and Environmental Sciences
Auburn University at Montgomery
Montgomery, AL
I've been searching for a flipped classroom experience for my nonmajor environmental biology class that demonstrates HOW plants store carbon. LOVE THIS!