7th Grade Metabolic Reactions - MS-LS1-3, MS-LS1-5, MS-LS1-7, MS-PS1-1, MS-PS1-2
Unit Overview

7.3 Metabolic Reactions

How do things inside our bodies work together to make us feel the way we do?

Unit Summary

This unit on metabolic reactions in the human body starts out with students exploring a real case study of a middle-school girl named M’Kenna, who reported some alarming symptoms to her doctor. Her symptoms included an inability to concentrate, headaches, stomach issues when she eats, and a lack of energy for everyday activities and sports that she used to play regularly. She also reported noticeable weight loss over the past few months, in spite of consuming what appeared to be a healthy diet. Her case sparks questions and ideas for investigations around trying to figure out which pathways and processes in M’Kenna’s body might be functioning differently than a healthy system and why.

Students investigate data specific to M’Kenna’s case in the form of doctor’s notes, endoscopy images and reports, growth charts, and micrographs. They also draw from their results from laboratory experiments on the chemical changes involving the processing of food and from digital interactives to explore how food is transported, transformed, stored, and used across different body systems in all people. Through this work of figuring out what is causing M’Kenna’s symptoms, the class discovers what happens to the food we eat after it enters our bodies and how M’Kenna’s different symptoms are connected.

Additional Unit Information

Next Generation Science Standards Addressed in this Unit

Performance Expectations

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This unit builds toward the following NGSS Performance Expectations (PEs): 

  • MS-LS1-3: Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.
  • MS-LS1-5: Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms.
  • MS-LS1-7: Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.
  • MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures.*
  • MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.*

*This unit reinforces these NGSS PEs that students should have previously developed. In the OpenSciEd Scope and Sequence, these are first built in Unit 7.1. In this new context of metabolic reactions, students will engage in the analysis and interpretation of various forms of data on how molecules change or do not change as they move through digestion. Chemical reactions starting in our mouths and stomachs and continuing throughout the rest of the digestive system drive this change, breaking down large food molecules into smaller ones. Some molecules, like fiber, stay the same throughout digestion and, therefore, do not undergo chemical reactions.

Disciplinary Core Ideas

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The current version of the unit expands students’ understanding of metabolic reactions, which include these Grade 6-8 DCI elements: 

LS1.A Structure and Function

LS1.B Growth and Development of Organisms

  • The growth of an animal is controlled by genetic factors,* food intake, and interactions with other organisms, and each species has a typical adult size range.

LS1.C Organization for Matter and Energy Flow in Organisms 

  • Within individual organisms, food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules, to support growth, or to release energy. 

PS3.D Energy in Processes and Everyday Life

  • Cellular respiration in plants and* animals involves chemical reactions with oxygen that release stored energy. In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials.   

*There is a slash through the pieces of the DCIs that are not developed in this unit. In the OpenSciEd Scope and Sequence, students will develop an understanding of genetic factors in the OpenSciEd Unit 8.5, how plants do chemical reactions to obtain and store energy in the subsequent OpenSciEd Unit 7.4, and interactions with other organisms in the ecosystem dynamics in OpenSciEd Unit 7.5.

In addition, this unit introduces the concept of food as fuel and lays the groundwork for future units in which students figure out that both food and other sources of fuels are sources of matter and sources of energy, drawing connections between chemical reactions that transfer and convert energy in living and nonliving systems. This connects to the idea identified on page 196 of Framework for K–12 Science Education (National Research Council, 2012): “By middle school, a more precise idea of energy—for example, the understanding that food or fuel undergoes a chemical reaction with oxygen that releases stored energy—can emerge.” 

You can view the placement of this OpenSciEd Unit 7.3 and associated units within the OpenSciEd Middle School Scope and Sequence

Science & Engineering Practices

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  • Developing & Using Models
  • Analyzing & Interpreting Data
  • Engaging in Argument from Evidence

Crosscutting Concepts

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  • Systems & System Models
  • Structure & Function

Connections to Nature of Science

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Which elements of the Nature of Science are developed in the unit?

  • Science investigations are guided by a set of values to ensure accuracy of measurements, observations, and objectivity of findings. (NOS-SEP)
  • Science limits its explanations to systems that lend themselves to observation and empirical evidence. (NOS-CCC)

How are they developed?

  • Students plan and carry out several investigations that require accurate measurements, clear descriptions of observations, and control conditions.
  • Students gather many forms of data about M’Kenna’s digestive system to serve as evidence supporting their explanation for why it is not functioning like a healthy system does.


Unit Placement Information

What is the anchoring phenomenon and why was it chosen?

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The anchoring phenomenon in this unit is a real case study of a middle-school girl named M’Kenna, whose symptom reports motivate students to figure out how the body’s subsystems interact to rearrange food through chemical reactions forming new molecules that can support growth and release energy.


Each OpenScied unit’s anchoring phenomenon is chosen from a group of possible phenomena after analyzing student interest survey results and consulting with external advisory panels.  We also chose M’Kenna’s case (celiac disease) as the anchor for this unit for these reasons:

  • We were fortunate to have access to some of M’Kenna’s real health data for classroom use.
  • The symptoms M’Kenna was experiencing are relatable to many students and impact multiple body systems.
  • The celiac disease pathology aligns well to the science ideas in this unit such as figuring out how food is rearranged through chemical reactions and how the body is a system of interacting subsystems composed of cells. Celiac disease is a condition that affects the structure and function of the small intestine. This prevents proper absorption of nutrients and is caused by eating gluten-containing foods.

How is the unit structured?

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This unit is organized into two lesson sets. In the first lesson set, students figure out how a healthy digestive system breaks down food into smaller molecules, which are then absorbed into the blood in the small intestine. M’Kenna’s body is breaking down food into small molecules, but not all of those molecules are absorbed by her small intestine. This is because her small intestine has a major structural difference from a healthy small intestine. M’Kenna’s small intestine is smooth, and an intestine with proper function has many finger-like folds. Students figure out that the folds create more surface area through which food molecules can pass. Consequently, her solid waste contains not only fiber, like a healthy body’s waste does, but also useful molecules that were not absorbed by her body, including glucose, amino acids, and fatty acids.

In the second lesson set, students develop models of various pathways showing how food molecules are rearranged in the body through chemical reactions to create energy, store matter for later use, and use matter for growth within a body system. Then they apply these ideas back to M’Kenna’s case to connect to how different body systems work together and can explain the way that M’Kenna is feeling.

In the third lesson set, students apply the models they have built to other living things besides humans and use what they have learned on a summative assessment about bear hibernation.

Where does this unit fall within the OpenSciEd Scope and Sequence?

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This is the third unit in the 7th grade scope and sequence for OpenSciEd. This unit directly builds off Disciplinary Core Ideas (DCIs), Crosscutting Concepts (CCCs), and Science and Engineering Practices (SEPs) developed in two prior units:

  • In the Healing Unit, students figure out that the body is a system of multiple interacting subsystems, and that these subsystems are groups of cells that work together to form tissues that are specialized for particular body functions. Students figure out interactions between cells and systems in the context of repair and growth related to the circulatory, muscular and nervous systems. In this unit, students figure out interactions between cells, tissues, organs and systems in the context of using and storing food for energy related to the digestive, excretory, circulatory, muscular and respiratory systems.
  • In the Bath Bombs Unit, students figure out how atoms that make up molecules can be rearranged. In this unit, students extend that model to see how chemical reactions occur in cells in living things as they process food. Students figure out what kinds of molecules are used in cells to get energy that is transferred in chemical reactions. The complexity of the molecules students investigate also increases: in the Bath Bombs Unit the molecules are relatively simple structures, made of a few atoms, while many of those investigated in this unit have extended repeating sub-structures made of many more atoms.

Also, students will use the ideas they build in this unit to support their work in future units:  

  • Work with food molecules and chemical reactions within living things will continue in the Maple Syrup Unit.

In the Muscles Unit students investigate how genetic information plays a major role in how the building blocks of proteins are rearranged and how the combination of local environmental effects and genetic influences on plant growth, in musculature in animals, and other trait variations in animals.

What mathematics is required to fully access the unit’s learning experiences?

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In Lesson 8 students use a NetLogo simulation to discover the relationship between the rate of food absorption and the height of villi that line the small intestine. Prerequisite math concepts that may be helpful include:

  • CCSS.MATH.CONTENT.6.NS.C.8: Solve real-world and mathematical problems by graphing points in all four quadrants of the coordinate plane.
  • CCSS.MATH.CONTENT.6.RP.A.2: Understand the concept of a unit rate a/b associated with a ratio a:b with b ≠ 0, and use rate language in the context of a ratio relationship. 
  • CCSS.MATH.CONTENT.7.SP.C.6: Approximate the probability of a chance event by collecting data on the chance process that produces it and observing its long-run relative frequency, and predict the approximate relative frequency given the probability. 
  • CCSS.MATH.CONTENT.7.SP.C.8.C: Design and use a simulation to generate frequencies for compound events.

Students analyze and interpret M’Kenna’s height and weight growth charts in Lesson 10. Prerequisite math concepts that may be helpful include:

  • CCSS.MATH.CONTENT.6.SP.B.5.C: Giving quantitative measures of center (median and/or mean) and variability (interquartile range and/or mean absolute deviation), as well as describing any overall pattern and any striking deviations from the overall pattern with reference to the context in which the data were gathered. 

In addition, within the domain of Measurement and Data in the Common Core Mathematics Standards, students will be drawing on what they have learned across a number of standards under the category of Represent and Interpret data for Grades 1-5 when they are generating and interpreting the tables and graphs of their data collected from the simulation and during analysis of several food molecule graphs in many lessons across the unit.

What modifications will I need to make if this unit is taught out of sequence?

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This is the third unit in 7th grade in the OpenSciEd Scope and Sequence. Given this placement, several modifications would need to be made if teaching this unit earlier in the middle school curriculum. These include:

  • Introducing the students to the concept of a Driving Question Board and a shared set of classroom norms. This would not be necessary if taught after other OpenSciEd units.
  • Supplemental teaching of the nature of matter, so that students see matter as made of particles.
  • Supplemental teaching of the foundations for chemical reactions in PEs MS-PS1-1 Develop models to describe the atomic composition of simple molecules and extended structures and MS-PS1-2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. This unit is designed to come directly after two units involved in the foundations of chemical reactions and explicitly builds on those understandings. It is critical to note that students need the idea of chemical reactions and the idea that matter can be rearranged through these reactions yielding resultant materials with different properties to develop the explanations in this unit.

Supplemental teaching of PEs MS-LS1-1 Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells and MS-LS1-2 Develop and use a model to describe the function of a cell as a whole and ways the parts of cells contribute to the function. This unit does not introduce cells to students. It uses that prerequisite knowledge to build understanding that the organization of the body goes from cells, to tissues, to organs, to subsystems to multiple subsystems working together in one body system.

How do I shorten or condense the unit if needed? How can I extend the unit if needed?

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The following are example options to shorten or condense parts of the unit without completely eliminating the important sensemaking for students.

  • Lesson 8: There is an assessment opportunity for students to argue from evidence for the diagnosis that is most likely causing M’Kenna’s symptoms. Students also are able to give peer feedback by comparing and critiquing their peer’s arguments. Either the assessment task and/or the peer feedback opportunity could be skipped.
  • Lesson 11: Instead of conducting the experiments “Burning Fat in Open and Closed Systems” and “Burning Fat  in Closed Systems and Measuring Gases”, students could watch the videos provided to collect data and make observations.
  • Lesson 14: If you are short on time this lesson could be skipped. It’s an opportunity for students to investigate if all animals do chemical reactions to get energy the same way as humans. Students investigate an organism of their choice to broaden out their model ideas and compare and contrast other living things such as spiders and bacteria.

To extend or enhance the unit, consider the following:

  • Lesson 8: During the simulation Connecting the Structure of Villi to Their Function, you could extend students’ explanation to include the idea of surface area. There are additional experiments around surface area to volume ratio and the size of cells that is most efficient for absorption using agar cubes of various sizes, a PH indicator and vinegar or other acid. Cut agar cubes made with a pH indicator of different sizes and place them into vinegar. Over time you will see how much of the solution diffusers into each cube. The simulation in the unit shows the size of cells remaining constant when the villi height is increased, but surface area to volume experiments could help answer additional questions such as, “What would happen to percent absorption if the size of the individual cells was increased?” or “Why are cells inside our body so small?” Make sure your students have the necessary math skills needed to understand the surface to volume ratio concept.
  • Lesson 13: In the activity section “Develop individual explanations for M’Kenna’s other symptoms” you could enhance this by building out a more robust model for the nervous system as a class for explaining her symptom of brain fog. This could answer questions such as, “What does our brain need? What makes up our nervous systems and how is it connected to the other body systems?” as well as providing opportunities for connections back to OpenSciEd Unit 6.6: How do living things heal? (Healing Unit).
  • All lessons: Remove scaffolds provided with Science and Engineering Practices as a way to give students more independent work with the elements of these practices. 

Unit Acknowledgements

Unit Development Team

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  • Tara McGill, Unit Lead, Northwestern University
  • Michael Novak, Field Test Unit Lead, Northwestern University
  • Kate Cook-Whitt, Writer, Maine Mathematics and Science Alliance
  • Kathryn Fattalah, Writer, The Nora Project
  • Emily Harris, Writer, BSCS Science Learning
  • Lindsey Mohan, Writer, BSCS Science Learning
  • Jamie Noll, Writer, Northwestern University
  • Barbara Taylor, Writer, Charles A. Dana Center at University of Texas Austin
  • Heather Galbreath, Pilot Teacher, Lombard Middle School
  • Michael Clinchot, Teacher Advisor, John D. O’Bryant School of Mathematics and Science
  • Nicole Vick, Reviewer, Abingdon-Avon High School
  • Betty Stennett, Reviewer, BSCS Science Learning
  • Katie Van Horne, Assessment Specialist
  • Kelsey Edwards, Project Coordinator, Northwestern University
  • Barbara Hug, Unit Advisory Chair, University of Illinois at Urbana-Champaign

Production Team

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BSCS Science Learning

  • Natalie Giarratano, Copyeditor, Independent Contractor
  • Stacey Luce, Editorial Production Lead
  • Valerie Maltese, Marketing Specialist & Project Coordinator
  • Alyssa Markle, Project Coordinator
  • Chris Moraine, Multimedia Graphic Designer

Additional Acknowledgements

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This unit was adapted from A Medical Mystery, originally developed by BSCS Science Learning in partnership with Oregon Public Broadcasting. Used with permission. A Medical Mystery was developed as part of the project, Three-dimensional teaching and learning: Rebuilding and researching an online middle school science curriculum (3DMSS) supported by the National Science Foundation under grant number 1502571. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Unit External Evaluation


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EdReports awarded OpenSciEd an all-green rating for our Middle School Science Curriculum in February 2023.  The materials received a green rating on all three qualifying gateways: Designed for the Next Generation Science Standards (NGSS), Coherence and Scope, and Usability. To learn more and read the report, visit the EdReports site.

Achieve's Science Peer Review Panel

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An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has been identified as a quality example of a science unit. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.

ed report
Unit standards

This unit builds toward the following NGSS Performance Expectations (PEs) as described in the OpenSciEd Scope & Sequence:

  • MS-LS1-3
  • MS-LS1-5
  • MS-LS1-7
  • MS-PS1-1
  • MS-PS1-2
Reference to kit materials

The OpenSciEd units are designed for hands-on learning and therefore materials are necessary to teach the unit. These materials can be purchased as science kits or assembled using the kit material list.