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Food For Thought: What fuels us? Glucose, the endocrine system, and health

Lesson 1: Why is glucose important for the body and brain?

I. Overview The purpose of this lesson is to introduce the driving question of the unit, “What fuels us?” Through a

series of activities, students actively participate in examining how the body uses its main energy source,

glucose. First, students calculate and draw models exhibiting the disproportionate distribution of

glucose throughout the body, and discuss why certain organs may require more energy than others.

Second, students analyze and interpret data to explain the role of glycogen and glucose in maintaining

blood glucose homeostasis.

Connections to the driving question Lesson 1 introduces the driving question “What fuels us?” and lays the foundation from which the

following lessons build. The aim of this lesson is to stress the importance of glucose as the body’s

primary energy source and how it is utilized in the human body during certain circumstances.

II. Standards

National Science Education Standards 12AS12.4 Mathematics is essential in scientific inquiry. Mathematical tools and models guide

and improve the posing of questions, gathering data, constructing explanation and

communicating results.

12CLS5.4 The complexity and organization of organisms accommodates the need for obtaining,

transforming, transporting, releasing, and eliminating the matter and energy used to sustain the

organism.

Benchmarks for Science Literacy The Human Organism: Basic Functions

The human body is a complex system of cells, most of which are grouped into organ systems

that have specialized functions. These systems can best be understood in terms of the essential

functions they serve for the organism: deriving energy from food, protection against injury,

internal coordination, and reproduction. 6C/H6 (SFAA)

Common Themes: Models

A mathematical model may give insight about how something really works or may fit

observations very well without any intuitive meaning. 11B/H1b

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Communication Skills

Make and interpret a scale drawing. 12D/H1

III. Learning Objectives

Learning objective Assessment Criteria Location in

Lesson

Explain that the body

allocates energy/glucose to

organs disproportionately.

Student glucunculus is drawn accurately

according the calculations of glucose use by

each organ.

Student glucunculus shows that the brain,

heart, liver, and kidneys have the highest

energy use for their relative mass.

Associated Materials: U7_L1_Table_EnergyConsumption&Weight

Activity 1

Explain homeostasis in the

context of glucose: Energy

can be regulated in the body

by storing and breaking

down glucose.

Students will use the CER framework to explain

that:

When blood glucose levels increase after

eating or decrease after exercise, there are

mechanisms in place that return blood

glucose levels to a set range.

Glycogen is a storage form of glucose. After

eating, glycogen levels in the liver increase as

glucose (broken down from food) is stored.

During exercise, glycogen stores in the brain,

muscle, and liver are broken down to release

glucose to produce energy.

Glycogen cannot be used directly for energy,

it must be broken down first into glucose

molecules.

Associated Materials: U7_L1_StudentSheet_ConstructingExplanations

Activity 2

Explain that glucose can only

pass a cell membrane via

glucose transporters

(Important for Lesson 2)

Students will use the CER framework to explain

that:

Glucose transporters are used to actively

bring glucose into cells.

Some cells, such as brain, muscle, and heart

cells have more glucose transporters

Activity 2

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compared to other cells.

A decrease in glucose transporters on brain

cells can have detrimental health

consequences.

Associated Materials: U7_L1_StudentSheet_Extension

IV. Adaptations/Accommodations If time is limited for lesson 1, fill out the right side of U7_L1_Table_EnergyConsumption&Weight and make copies. Students are still using mathematical and computational skills, but are able to spend less time doing so. Student may also complete this worksheet for homework.

V. Timeframe for lesson Opening - Cellular Respiration Review: 10 - 15 minutes

Activity 1 - Glucunculus Drawing: 40 minutes

Activity 2 - Constructing Explanations Activity: 40 minutes

Conclusion of Lesson: 10 – 15 minutes

VI. Advance prep and materials

Opening Activity: Cellular Respiration Review

Materials:

U7_L1_Image_HowDoWeGetEnergy

U7_L1_Image_OnlyGlucoseInBlood

Preparation:

Project images via projector to support instruction.

Activity 1: Glucunculus Drawing

Materials:

Calculators

U7_L1_Image_SensoryHumunculus

U7_L1_Table_EnergyConsumption&Weight OR

U7_L1_Table_EnergyConsumption&Weight_Guided

U7_L1_Image_GluncunculusExample

U7_L1_Resource_FinalGlucunculus (ONLY use as resource for teacher)

Whiteboards (or poster paper)

Markers

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Preparation:

Print out U7_L1_Table_EnergyConsumption&Weight for every student.

Project images via projector to support instruction.

Activity 2: Constructing Explanations

Materials:

U7_L1_StudentSheet_ConstructingExplanations

U7_L1_StudentSheet_Extension

Preparation:

Print U7_L1_StudentSheet_ConstructingExplanations and U7_L1_StudentSheet_Extension for every student.

Conclusion

Materials:

U7_L1_Image_GlucoseTransporter

U7_L1_Reading_Iceman

Preparation:

Project image via projector

Copy reading (1 per student or class set)

Extension: Application to evolution

Materials:

U7_L1_Reading_GlucoseEvolution

U7_L1_Reading_GlucoseEvolution_AP

U7_L1_Reading_RawFood

U7_L1_StudentSheet_Readings

Preparation:

Copy readings (1 per student or class set)

VII. Resources and references

Teacher resources Access the document U7_L1_Resource_FinalGlucunculus to see what a finished “glucunculus”

should look like.

References Data for the “Glucunculus” Activity

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McClave SA, Snider HL. (2001). Dissecting the energy needs of the body. Current Opinions in Clinical Nutritional Metabolic Care. 4(2): 143-7.

U7_L1_Reading_Iceman article written based on:

Angier, J. (2008, March 7) Iceman on Everest: ‘It Was Easy’. ABC News. Retrieved from:

http://abcnews.go.com/Health/story?id=4393377

Hof, W., Hopman, M. (2010, November 11). Wim Hof. Retrieved from:

http://tedxtalks.ted.com/video/TEDxAmsterdam-Wim-Hof-113010

U7_L1_Reading_GlucoseEvolution & U7_L1_Reading_GlucoseEvolution_AP article written based on:

Fedrigo, O., Pfefferle, A. D., Babbitt, C. C., Haygood, R., Wall, C. E., & Wray, G. A. (2011). A potential role for glucose transporters in the evolution of human brain size. Brain, Behavior and Evolution, 78(4), 315-326.

Isler, K., van Schaik, C. (2006). Costs of encephalization: The energy trade-off hypothesis tested

on birds. Journal of Human Evolution, 51, 228-243.

U7_L1_Reading_RawFoodReading article written and based on:

Taken from: Gibbons, Ann. (2012) Raw Food Not Enough to Feed Big Brains. Science Now. Retrieved from: http://news.sciencemag.org/sciencenow/2012/10/raw-food-not-enough-to-feed-big-.html

U7_L1_StudentSheet_ConstructingExplanations - graph data for Figures E & F modified from:

Blood sugar is stable. Retrieved from http://www.medbio.info/horn/time%203-

4/homeostasis1.htm

What’s fuel for the body is fuel for the brain: a story of glycogen. (2012, February 12). Retrieved

from http://scientopia.org/blogs/scicurious/2012/02/29/whats-fuel-for-the-body-is-fuel-for-

the-brain-a-story-of-glycogen/

U7_L1_StudentSheet_Extension

Image in Evidence A retrieved from: https://imcurious.wikispaces.com/Midterm+Exam+2010+Review+P2

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VIII. Lesson Implementation

Opening of Lesson: Cellular Respiration Review Depending on the progression and type of science class, the teacher can choose the depth at which

cellular respiration will be discussed in relation to glucose. Materials and discussion questions are

provided here to help facilitate discussion on the role of glucose in the body.

Use U7_L1_Image_HowDoWeGetEnergy to help guide a discussion on cellular respiration. Project the

visual so that students can follow the diagram during class discussion. The series of questions below

aims to link the processing of food at a large scale to the formation of ATP at a cellular scale. The

discussion’s level of detail will depend on the needs of the class.

How does the body get energy?

What happens to food after we eat it?

What happens after it is digested? Where does it go?

Does glucose stay in the bloodstream?

How does the cell get energy out of glucose?

Why is it called cellular respiration? (Think about respiration in the lungs)

What is ATP?

What are the major “ingredients” or reactants needed for cellular respiration to occur? What are the major products?

Project the image U7_L1_Image_OnlyGlucoseInBlood. Students should be able to describe that by the

time it enters the bloodstream, all food is broken down into micronutrients. Students should also

understand that any type of carbohydrate that is eaten will eventually be digested and converted to

glucose in the digestive system.

Crosscutting Concepts: Scale, Proportion, and Quantity An advantage of this unit is the ability to link phenomena between the micro and

macro level. For instance, the energy in the food we eat can only be harnessed at a

molecular and cellular level. Additionally, students will learn that the proportion and

quantity of energy utilized by the body changes based on the specific activity of an

organism.

Activity 1: “Glucunculus” Drawing Project the image U7_L1_Image_SensoryHumunculus. Ask students why this person is drawn so

disproportionately? What do you think the larger parts of the body represent? After hearing responses,

tell the students that this image is a “sensory humunculus.” It visually demonstrates the

disproportionate number of “touch receptors” located in different parts of the body.

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To get students to begin thinking about glucose use in the body, ask:

Sensory receptors are disproportionate in the body. Do you think glucose is distributed equally across organs in the body? Do some organs in the body use more energy than others? Which organs do you think would be represented bigger in a “glucunculus?”

Pass out the worksheet: U7_L1_Table_EnergyConsumption&Weight. Tell students they will be calculating the energy needs of different organs in the body. Have students individually calculate the percentages on the worksheet.

Teacher Pedagogical Content Knowledge If students are struggling calculating percentages, model the process for students by

calculating the percentage of boys and girls in the classroom on the whiteboard; this

gives students necessary scaffolding, but also allows students to generate

mathematical understanding of data on their own. If additional scaffolding is needed, a

more guided version of this student sheet can be used:

U7_L1_Table_EnergyConsumption&Weight_Guided.

As a class, discuss what these calculated ratios mean.

Teacher Content Knowledge If the human body distributed energy throughout the body evenly, then every organ

would have a ratio of about 1. Therefore, any ratio under 1 signifies that a tissue is

using less than its expected weight would indicate. Any ratio above 1 signifies that the

tissue is using more energy than its weight would indicate. For instance the % energy

consumption/% weight for the brain is 10/1. That means the brain uses 10 times more

energy than its weight would indicate.

After students have completed the table ask them:

Can we create a “glucunculus” with our ratios? Inform students that the goal of the next activity is to develop a “glucunculus” that visually illustrates how glucose is allocated disproportionately in the body.

Working in groups of 3-4 and using the data from their completed table, have students draw a “glucunculus” on whiteboards. Scaffold and assess student progress and understanding by walking about the room observing and questioning students.

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Teacher Content Knowledge In observing this unit in action, students have found it difficult to draw a picture of the

body that is so incredibly disproportionate. For instance, despite having calculated that

the heart needs to be 18 times larger than normal, students are hesitant to make a

drawing that is so grossly disproportionate. Therefore, it helps to preface the activity

with showing students image U7_L1_Image_glunculusexample to show students how

to accurately portray organs in their model.

When groups are finished drawing the “glucunculus,” wrap up the activity with discussion. Ask students:

Explain why you made the glucunculus the way you did?

If the drawings differ from group to group ask students, “Why does your drawing look different even though they used the same data? Would you change your drawing? Can you defend why you drew it this way?

Are you surprised by the size of any structure in these drawings?

Which organs require the most glucose in the body?

Why do you think that these organs require this much energy?

Why does the brain require so much energy?

For an example of the final glucunculus, teachers can reference U7_L1_Resource_FinalGlucunculus.

Activity 2: What happens when the body is not at rest?

Teacher Pedagogical Content Knowledge It is helpful to choose a limited amount of vocabulary words to be the focus of a unit.

In this way students gain an in-depth understanding of the important terms that

emphasize the main ideas of the unit. The main vocabulary words should be brought

up frequently throughout a unit.

For this unit, the main vocabulary words are: (Words in bold introduced in Activity 2).

Homeostasis

Negative feedback

Insulin vs. glucagon

Fight-or-flight response

Pre-Activity Homework:

To help support Activity 2, tell students that for homework they need to take their pulse (count the

beats for 30 seconds) every minute for 10-15 minutes. They should graph their results and bring them in

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the next day. Students will observe a wave-like pattern in their graph. This will be an excellent starting

point to discuss homeostasis in Activity 2.

Activity 2: The next day, have students take out their graphs showing changes in their pulse over 15 minutes. What do your graphs look like? Draw a quick example on the board. Write on the board or via the projector the question:

The phenomena illustrated in the graph reveal a very important concept true to living organisms.

Describe what you think this concept is by looking at the graph you constructed.

Have students work in partners for one or two minutes as they attempt to describe the phenomenon

(homeostasis) by looking at the graph. Have students share a couple of their descriptions with the class

and write the important points on the board. Next, present the definition of homeostasis.

Homeostasis is the ability of an organism to maintain a constant internal state.

Provide further examples of homeostasis for students (body temperature, glucose levels, blood

pressure, blood pH, water, calcium, breathing .etc). If not already brought up, tell students that they are

going to discuss homeostasis in light of the molecule glucose. Inform students that the data they had

analyzed to draw the “glucunculus” was from a person at rest. Ask the students if they believe that

muscles require more energy when a person is exercising. Follow this response up with the central

question of the activity:

Is the body able to keep our energy levels – our glucose levels - stable? How does the body acquire more

energy during exercise or when fasting?

Pass out U7_L1_StudentSheet_ConstructingExplanations to the students. Have students work in

groups of four to complete the sheet. Students will construct arguments using claim, evidence, and

reasoning (CER).

Scientific Practices: Constructing explanations and engaging in

argument from evidence An important goal of science teaching is for students to use their understanding of

science and the evidence available to them to construct logical and coherent

explanations. Students are given the scaffolding to form explanations and arguments

through the claim, evidence, reasoning framework (CER).

Claim: Statement of argument.

Evidence: Select specific concrete evidence that supports the claim.

Reasoning: Explain why the evidence supports the claim. Usually involves

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scientific principles or prior known scientific knowledge.

For more information on presenting conclusions and arguments in the CER format visit: http://learningcenter.nsta.org/products/symposia_seminars/NSTA/files/HowDoYouKnowThat--HelpingStudentsWriteAboutClaimsandEvidence_12-12-2012.pdf. Additionally, an example of a CER is provided below.

First question from U7_L1_StudentSheet_Constructing Explanations: Is the body able to keep blood

glucose levels at homeostasis?

CLAIM: The body works to keep blood glucose levels at a stable level, at homeostasis.

EVIDENCE: In Figure A, after a meal, blood glucose levels rise. However, these levels soon return

to a stable level. In Figure B, during exercise, glucose levels decrease. However, these levels

soon return to a generally stable state, even during continued exercise.

REASONING: Homeostasis is the ability to keep the body’s internal environment at a fairly

constant internal state in varying environmental conditions. In both figures (A and B) the body is

under different circumstances – eating a meal or exercising. Although these conditions do

initially cause blood glucose to deviate from a constant internal state, soon thereafter, glucose

levels return to a relatively stable state.

When students complete the first activity, present them with U7_L1_StudentSheet_Extension. This

worksheet covers the third learning objective (necessary to prepare students for Lesson 2) in which

students explain that glucose can only pass into and out of cells through glucose transporter proteins.

Like the first student sheet, students will analyze data to develop this consensus. Students may present

their findings from the extension activity to the rest of the class during the conclusion of the lesson.

Conclusion Guide a whole-class discussion over the two questions in the worksheet. Use this conclusion time to

provide further explanation on homeostasis and the role of glucose. During Activity 2, it may have been

observed that students are constructing differing claims. This is a great opportunity to have students

present and argue their claims amongst the class and to discuss the nature of science. Students are

using the same pieces of evidence, but are coming to different conclusions, highlighting the importance

of reasoning in an argument. Furthermore, students may not be convinced by a claim due to the lack or

ambiguity of evidence. Encourage students that this is a perfectly valid stance to take, as the scientific

community needs multiple critically reviewed pieces of evidence before accepting a theory.

Below are two meaningful, relatable, and engaging examples of glucose homeostasis to aid whole-class

discussion.

Discuss how glucose and glycogen are utilized during exercise. Students find this topic

interesting as they can relate it to their involvement in sports, dance, exercise, etc.

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(Optional) Inform students about Wim Hof, the “Ice Man.” Wim Hof can withstand extremely

cold temperatures. This example can reveal that glucose can be made available to be

metabolized in order to release heat to keep the internal temperature of the body at

homeostasis. Read the article about “Iceman” (U7_L1_Reading_Iceman) to learn more about

Wim Hof or search him on the Internet.

If time is available, initiate discussion on glucose transporters – the means by which glucose can pass in

and out of cells. If any students have completed L1_StudentSheet_Extension activity, ask them if they

are willing to briefly explain to the rest of the class what they discovered about the glucose transporter

protein.

Continue to provide instruction on glucose transporters. Teachers may find

U7_L1_Image_GlucoseTransporter as a helpful visual aid for students. Teachers may also choose to

provide further notes or examples when discussing the role of glucose transporters. Remember, glucose

transporters are introduced to prepare students for a modeling activity in Lesson 2, and to reinforce the

semi-permeability nature of the cell membrane if covered previously.

Tell students that in the next lesson, they will explore how the body is able to accomplish glucose

homeostasis. Students will be introduced to the endocrine system and learn how the hormones insulin

and glucagon regulate glucose levels in the blood.

Assessment Activity 1: U7_L1_Table_EnergyConsumption&Weight (or the guided version)

Students should have completed table with accurately calculated (1) percentages and (2) ratios.

Questions following the table should be accurately answered. “Glucunculus” Drawing

Students should draw a glucunculus that accurately represents the disproportionate energy use in the body.

Informally assess group discussion and construction of the “glucunculus” by walking about the room observing and possibly questioning students about their reasoning in building their model.

Activity 2: U7_L1_StudentSheet_ConstructingExplanations & U7_L1_StudentSheet_Extension

Students should have well-formed arguments in response to the questions posed in the worksheet.

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Application to Evolution If students have covered evolution or if evolution will be covered later in the year, the following articles

provide terrific examples of the role that glucose has played in the evolution of human intelligence.

After reading these articles, “Iceman”, and doing the lesson activities, students can also complete the

student sheet (U7_L1_StudentSheet_Readings) which guides them to draw out the main ideas and

reflect on the material.

Reading: Raw food not enough to feed big brains (U7_L1_Reading_RawFood) Summary: In order to evolve a large brain that uses a large amount of energy, an organism

needs to be able to efficiently absorb the calories it consumes. It is believed that by cooking

foods, humans were able to more rapidly acquire calories and use less energy in acquiring food

as well as digesting food. Cooking, this article states, gave humans the energy necessary to fuel

a highly metabolic brain.

Reading: How could walking upright have helped in the evolution of human intelligence? (U7_L1_Reading_GlucoseEvolution or U7_L1_Reading_GlucoseEvolution_AP) Summary: Scientists are studying glucose metabolism as a variable in the evolution of human

intelligence. It has been shown that walking upright in a human fashion requires 75% percent

less energy than walking quadrapedally. This “extra” energy could be allocated elsewhere in our

hominin ancestors. A study reveals that an increased expression of glucose transporters in the

brain has gone under positive selection during early human evolution.