MS-LS1-7: Modeling How Food Is Rearranged for Growth and Energy
In plain English: MS-LS1-7 is the NGSS middle school performance expectation that asks students to develop a model of how food molecules are broken apart and put back together into new molecules as they move through an organism. The new molecules build the body for growth, or react to release energy. It is usually taught in grade 6, 7 or 8 life science.
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.
Clarification Statement: Emphasis is on describing that molecules are broken apart and put back together and that in this process, energy is released.
Assessment Boundary: Assessment does not include details of the chemical reactions for photosynthesis or respiration.
Next Generation Science Standards · Disciplinary Core Idea: From Molecules to Organisms: Structures and Processes · Official standard
Students build and use a model of what happens to food inside an animal. Food is made of molecules, groups of atoms (the tiny particles all matter is made of) joined together. Most food molecules are large: starch is a long chain of sugar units, and proteins are chains of smaller building blocks called amino acids. In digestion, the body breaks these large molecules into small ones. The blood carries the small molecules to cells. There, chemical reactions (changes in which atoms are rearranged to form new molecules) do one of two jobs: they join small molecules into new large molecules the body needs for growth and repair, or they combine sugar with oxygen to make carbon dioxide and water, which releases energy. Atoms are never created or destroyed along the way; they are only rearranged.
The NGSS Clarification Statement says: "Emphasis is on describing that molecules are broken apart and put back together and that in this process, energy is released." The Assessment Boundary says: "Assessment does not include details of the chemical reactions for photosynthesis or respiration." So this page uses paper-clip and bead models, flow diagrams and simple mass data, and never asks for chemical formulas or equations. All data on this page are invented for teaching. No food is eaten or handled: food labels are paper cards.
Learning Objectives
By the end of this lesson, students will be able to:
Develop a model showing that digestion breaks large food molecules (starch, proteins) into small molecules (sugars, amino acids)
Use a model to show that cells join small molecules in new orders to make the body's own molecules for growth and repair
Use a model to show that sugar reacts with oxygen in cells, forming new molecules (carbon dioxide and water) and releasing energy
Track food matter through an animal with simple mass data, showing where the atoms go and that none are lost
Critique and revise a model that says food "turns into energy" or stays unchanged in the body
Prior Knowledge Required
Students should already be comfortable with:
Energy in animals' food is used for growth, repair, motion and body warmth 5-PS3-1
Matter is made of particles too small to see
In a chemical reaction, atoms are rearranged and the total number of atoms stays the same MS-PS1-5
Adding and subtracting decimals, and finding a simple percent
Show a photo of a baby goat next to the same goat one year later. Ask students to think, then share with a partner:
Warm-Up Prompt
"The goat gained many kilograms in a year, and it ate only plants. Where did the goat's new muscle and bone come from? Did the plants just pile up inside it, or did something happen to them?"
Record ideas on the board without correcting them. Many students say "the food turns into the goat" or "the food turns into energy." Tell the class they will build a model today that tests both ideas.
Direct Instruction15 minutes
Breaking apart and putting back together. Walk through Diagram 1 step by step. Define each word as you reach it: a molecule is a group of atoms joined together; a chemical reaction is a change that rearranges atoms into new molecules. Stress two ideas. First, the small molecules from digestion are not the final product: cells use them as building blocks or as fuel. Second, the atoms in food do not vanish. They end up in new body molecules, in carbon dioxide and water that leave the body, or in waste. Then show Diagram 2: the same building blocks, joined in a new order, make a different molecule with a new job.
Breaking apart: starch in a cracker
A cracker is mostly starch. In the class model, one starch molecule is a chain of 12 sugar units hooked together.
Result: Digestion unhooks the chain: 1 large molecule becomes 12 small sugar molecules. No sugar units are lost; they are only separated, so they can pass into the blood.
Putting back together: protein for growth
A protein in fish is modeled as 8 beads in the order A-A-B-C-A-D-B-C, where each letter stands for a kind of amino acid. A growing student's muscle needs a protein in the order D-A-C-A-B-C-A-B (Diagram 2).
Result: Digestion separates the 8 amino acids. Cells join the same 8 in the new order. Both chains have 3 of A, 2 of B, 2 of C and 1 of D, but the new chain is a different molecule with a different job.
Releasing energy: sugar and oxygen
During soccer practice, a player's leg muscle cells take in sugar molecules from the blood, and the lungs bring in oxygen.
Result: In the cells, sugar reacts with oxygen. Its atoms are rearranged into new, smaller molecules: carbon dioxide and water. Energy is released, which moves the muscles and warms the body. The carbon dioxide travels in the blood to the lungs and is breathed out.
Tracking matter: a hamster's day (invented data)
A young pet hamster eats 10.0 g of dry seed mix in one day. 2.0 g leaves in its droppings, and its body gains 0.5 g of new dry material.
Result: Absorbed: 10.0 - 2.0 = 8.0 g. Built into the body: 0.5 g. Used for energy: 8.0 - 0.5 = 7.5 g, whose atoms leave mostly as carbon dioxide and water. Only 0.5 ÷ 8.0 ≈ 6% of the absorbed food became new body material.
After each example, ask: "Which step is breaking apart, and which step is putting back together? Where are the atoms at the end?" Point out that "dry" mass means the mass with the water removed, so it counts the food's molecules and not the water in it.
Guided Practice15 minutes
Pairs analyze invented data for a young pet rat over four weeks as it grows to adult size. All masses are dry masses for one week.
Invented data: a young rat over four weeks (grams per week, dry mass)
Week
Food eaten
Droppings
New body material
1
105
21
12
2
112
22
10
3
119
24
6
4
119
24
0
For each week, find the food absorbed (eaten minus droppings).
Find the food used for energy (absorbed minus new body material).
Describe the pattern: as the rat nears adult size, what happens to the share of food used for growth?
Add arrows to a copy of Diagram 1 for week 1, writing the number of grams next to each arrow.
Check answers together: absorbed 84, 90, 95 and 95 g; used for energy 72, 80, 89 and 95 g. In week 4 all the absorbed food is used for energy or for repair, because the rat has stopped growing.
Independent Practice10-15 minutes
Each student draws a model for a chicken and rice dinner. The model must show: (1) the large molecules in each food (protein in the chicken, starch in the rice); (2) digestion breaking them into small molecules; (3) the blood carrying them to cells; (4) one path for growth or repair and one path that releases energy; and (5) where the atoms leave the body. Students label every arrow with what moves along it.
Circulate and ask: "Does any arrow make atoms disappear? Does any arrow turn matter into energy?" Students who finish early compare their model with Diagram 1 and add one thing Diagram 1 leaves out.
Closure5 minutes
Return to the goat from the warm-up. Exit ticket: "Use the words broken apart and put back together to explain where the goat's new muscle came from. Then name one place the atoms of the plants went that is not the goat's body."
Differentiation Strategies
For Struggling Students
Give a partly filled copy of Diagram 1 with word cards (digestion, blood, build, release energy, breathed out) to place in the boxes
Use only two colors of paper clips at first, then add more kinds of building blocks
Provide sentence frames: "Digestion breaks ___ into ___. Cells use them to ___ or to ___."
For Advanced Students
Ask students to explain why an animal that eats the same amount of food every week can still lose mass when it gets colder
Have students design a fair way to compare how much of its food a young animal and an adult animal turn into new body material
Ask students to add fat to Diagram 1: what small molecules would it be broken into, and what two jobs could they do?
Assessment Guidance
What to Look For
Check that models show two separate steps: breaking large molecules apart (digestion) and putting small molecules back together or reacting them with oxygen (in cells). Look for arrows that keep track of matter all the way out of the body. Listen for the ideas that food "turns into energy" or "turns into muscle" with no change, and ask students where the atoms are. Students do not need chemical formulas or equations.
02
Classroom Activities
3 Activities
1
Paper Clip Chains: Break Apart and Rebuild
20 minPairs
Pairs use paper clips as building blocks. A chain of hooked clips is a large food molecule; a single clip is a small molecule. Students digest two food molecules, then rebuild some pieces into body molecules and send others through the energy path.
Materials and Setup
Per pair: one "starch" chain of 10 white clips, one "protein" chain of 12 clips in four colors (4 red, 4 blue, 2 green, 2 yellow) hooked in the order shown on the setup card, a sticky note labeled "oxygen" for each energy step, and a "new body protein" card showing the order red-blue-red-green-blue-yellow-red-blue-green-red-yellow-blue
Safety: clips stay on the desk; no unbending clips into points
Procedure
Digest: unhook both chains completely and count the separate clips by color.
Grow: hook the 12 colored clips into the order on the "new body protein" card.
Release energy: take 4 white clips (sugars). For each one, place it on an "oxygen" sticky note and move both to the "breathed out as carbon dioxide and water" box, then make one tally mark on the "energy released" chart.
Store: hook the remaining 6 white clips into a short chain, the storage starch (called glycogen) that liver and muscle cells keep for later.
Count every clip at the end and compare with the start.
Discussion Questions
You started with 22 clips. How many are in your three places at the end (body protein, storage chain, breathed-out box)? What does that tell you about atoms?
The new body protein has the same number of each color as the food protein. Why is it still a different molecule?
The clips are not destroyed in the energy step. What does the tally mark stand for, and what in the model stands for the matter?
What part of real digestion does this model leave out?
Modification for Distance Learning
Students use small paper squares cut from four colors of paper, or a drag-and-drop slide with colored circles, and post a photo of each stage.
2
Food Label Detectives: Building Blocks and Energy
20 minGroups of 3-4
Groups read four invented food-label cards (paper only; no food in the room). They decide which food gives the most building blocks for new protein and estimate how much energy each serving can release. A Calorie on a food label is a unit of energy; the usual estimate is 4 Calories for each gram of carbohydrate (sugars and starch), 4 for each gram of protein and 9 for each gram of fat.
Label Cards (invented, per serving)
Card 1, plain oatmeal (40 g dry): carbohydrate 27 g, protein 5 g, fat 3 g
Card 2, sliced turkey (56 g): carbohydrate 2 g, protein 10 g, fat 1 g
Card 3, one medium apple: carbohydrate 25 g, protein 0 g, fat 0 g
Card 4, half an avocado (100 g): carbohydrate 9 g, protein 2 g, fat 15 g
Procedure
For each card, estimate the Calories with the 4-4-9 rule and record them in a table.
Rank the cards by protein, then by Calories.
For each card, draw a mini model: which large molecules are in it, what small molecules digestion makes, and which path in Diagram 1 each one mostly takes.
Discussion Questions
Which card gives the most building blocks for new muscle protein? Which gives the most energy? Are they the same card?
The apple has no fat and no protein but still has energy. Which molecules carry it?
Card 4 has less carbohydrate than Card 1 but more Calories. Use the 4-4-9 rule to explain why.
A food can support growth and release energy. Use one card to show both paths.
Modification for Distance Learning
Share the cards as images. Groups fill in a shared table and post their ranking with one sentence of reasoning.
3
Model Critique Gallery: Where Does the Sandwich Go?
20 minGroups of 3-4
Four invented student models of "what happens to a turkey sandwich" hang around the room. Each one has a problem. Groups rotate every 4 minutes, write one sticky-note critique per model, and then revise one model on chart paper.
The Four Models
Model W: sandwich → stomach → "turns into energy" → gone.
Model X: sandwich → stomach → blood → the turkey protein goes into the arm muscle unchanged.
Model Y: bread starch → sugars → cells → carbon dioxide and water + energy; nothing about growth.
Model Z: sandwich → small molecules → cells → new body protein; the arrows stop there, with no waste and nothing breathed out.
Critique Questions
Where in this model do the atoms go? Does any atom disappear?
Does the model show breaking apart and putting back together?
Does it show both paths (growth and energy) or only one? Is that a problem for this food?
Discussion Questions
Models W and X make opposite mistakes. Describe each mistake in one sentence.
Model Y is correct as far as it goes. What would you add for a 12-year-old who is still growing?
Which model was the hardest to fix, and why?
Modification for Distance Learning
Post the four models on a shared slide deck. Students add comments to each slide and submit one revised model.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: A Model of Food Moving Through an Animal
A flow model of food in an animal. Digestion breaks large food molecules into small ones, the blood carries them to cells, and cells either join them into new large molecules (growth and repair) or react sugar with oxygen, releasing energy and forming carbon dioxide and water. The atoms in food end up in the body, in breath, sweat and urine, or in droppings: none are lost.
Diagram 2: Bead Model of a Protein Rebuilt for Growth
The bead model from the second worked example. Each letter is one kind of amino acid. Digestion breaks the food protein into separate amino acids, and cells join the same 8 building blocks in a new order to make a muscle protein. The counts do not change; the order, and so the molecule, does.
04
Homework Assignment
~30 min
MS-LS1-7 Homework: Following Food Through the Body
Directions: All data are invented for practice. Draw a model where a problem asks for one, and label every arrow. You do not need chemical formulas. Show your arithmetic.
Part 1: Build the Model (Problems 1-2)
A potato is mostly starch. In a model, one starch molecule from the potato is a chain of 20 sugar units. (a) Draw the molecule before and after digestion. (b) How many separate sugar molecules are there after digestion? (c) Name two different things body cells can do with these sugar molecules.
A protein in lentils is modeled with 12 beads: 5 of type A, 2 of type B, 3 of type C and 2 of type D. A student proposes two possible hair proteins that the body could build from these exact beads, using all 12: Proposal 1 is D-C-A-A-B-C-A-D-A-C-B-A, and Proposal 2 is A-A-B-B-C-C-D-D-A-A-B-C. (a) Count each type in each proposal. (b) Which proposal is possible? (c) Explain why the hair protein is a new molecule even though no bead was added.
Part 2: Use Data (Problems 3-4)
A growing kitten eats 60 g of dry food in a day. 12 g leaves as droppings, and its body gains 5 g of new dry material. (a) How much food was absorbed? (b) How much was used to release energy? (c) What percent of the food eaten was used for energy, to the nearest percent? (d) Where do the atoms of that food go?
A cereal label (invented) lists, per serving: carbohydrate 24 g, protein 3 g, fat 1 g. (a) Use 4 Calories per gram of carbohydrate or protein and 9 per gram of fat to estimate the Calories in one serving. (b) Which nutrient gives the most Calories? (c) Which molecules from this cereal mostly support growth, and which mostly release energy?
Part 3: Critique and Explain (Problems 5-6)
A classmate says: "When you exercise, your body fat turns into energy and disappears." (a) What is wrong with this claim? (b) Revise it into a correct statement that uses the words molecules, oxygen and breathed out. (c) Draw a small model of your revised statement.
A silkworm caterpillar spins a cocoon and becomes a pupa, a resting stage that does not eat or drink. Inside the cocoon it builds wings, legs and antennae, then comes out as an adult moth. In an invented study, 20 pupae dried on their first day had a total dry mass of 5.0 g, and 20 similar pupae dried just before the moths came out had a total dry mass of 4.2 g. (a) Find the change in dry mass and the percent change. (b) The pupae built new body parts, yet lost dry mass. Use the idea of body molecules being broken apart and put back together to explain both facts. (c) Where did the missing matter go?
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Model
Shows breaking apart, putting back together and releasing energy, with labeled arrows
Shows some steps, or arrows are not labeled
Tracking Matter
Every atom is accounted for: body, breath, urine or droppings; correct arithmetic
Most matter tracked, or one arithmetic error
Explanation and Critique
Explains with evidence and corrects "turns into energy" ideas
Explanation is general or repeats the error in part
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data are invented. No chemical formulas are needed. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
In a model, one starch molecule is a chain of 15 sugar units. How many separate sugar molecules are there after digestion?
Answer: B
Digestion unhooks every sugar unit, so the chain becomes 15 separate sugar molecules. Choice A counts the 14 links between units instead of the units. Choice C treats the chain as unchanged, and choice D assumes each unit splits in two.
Question 2 of 20 · Multiple Choice
Which sentence best describes what cells do with amino acids from digested food when the body is growing?
Answer: D
Cells put amino acids back together in new orders to build the body's own proteins, such as muscle. Choice A skips the breaking-apart step. Choice B says matter turns into energy; in fact atoms are only rearranged while energy is released. Choice C ignores growth.
Question 3 of 20 · Multiple Choice
Muscle cells release energy from sugar during a race. Which new molecules form from the sugar and oxygen?
Answer: A
Sugar reacts with oxygen and its atoms are rearranged into carbon dioxide and water, while energy is released. Choice B lists building blocks and a food molecule, not products of this reaction. Choice D lists oxygen, which is used up in the reaction, not made.
Question 4 of 20 · Multiple Choice
A young guinea pig eats 30 g of dry food in a day (invented data). 6 g leaves in its droppings, and its body gains 1.5 g of new dry material. How many grams of the food were used to release energy?
Answer: C
Absorbed food is 30 - 6 = 24 g, and 24 - 1.5 = 22.5 g was used for energy. Choice A stops at the absorbed amount and forgets the growth. Choice B subtracts only the growth and forgets the droppings. Choice D subtracts the growth from the droppings.
Question 5 of 20 · Multiple Choice
When body cells use food molecules to release energy, where do most of the atoms of those molecules end up?
Answer: B
The atoms are rearranged into carbon dioxide and water, which leave mainly in the breath (water also leaves in sweat and urine). Choice A describes food that was never absorbed. Choices C and D treat atoms as if they could become energy, but energy is released while the atoms stay as matter.
Question 6 of 20 · Multiple Choice
A student's model says, "Food turns into energy." Which revision fixes the model?
Answer: A
Matter does not become energy in the body. Atoms are rearranged into new molecules, and the reactions release energy. Choices B, C and D keep the same error and only add where, which foods or when.
Question 7 of 20 · Multiple Choice
An invented food label lists carbohydrate 30 g, protein 4 g and fat 2 g per serving. Using 4 Calories per gram for carbohydrate and protein and 9 per gram for fat, about how many Calories is one serving?
Answer: D
30 × 4 + 4 × 4 + 2 × 9 = 120 + 16 + 18 = 154 Calories. Choice A adds the grams without converting. Choice B uses 4 Calories per gram for fat too. Choice C swaps the factors for protein and fat (9 for protein, 4 for fat).
Question 8 of 20 · Multiple Choice
A food protein is modeled as 8 beads: 4 of type A, 3 of type B and 1 of type C. After digestion, which chain could cells build from exactly these 8 beads?
Answer: C
Choice C has 4 A, 3 B and 1 C: the same building blocks in a new order. Choice A has 2 of C, so it needs a bead that was not there. Choice B has only 6 beads. Choice D has 4 B and no C.
Question 9 of 20 · Multiple Choice
An adult has stopped growing taller. Why does the adult still need to eat every day?
Answer: B
Even without growth, cells react sugar and other molecules with oxygen to release energy, and they rebuild worn-out molecules for repair. Choice C is wrong because atoms do not disappear; they leave in breath, urine and waste. Choices A and D ignore energy and repair.
Question 10 of 20 · Multiple Choice
A young rat eats 110 g of dry food in a week (invented data). 20 g leaves as droppings, and its body gains 9 g of new dry material. What percent of the absorbed food became new body material?
Answer: A
Absorbed food is 110 - 20 = 90 g, and 9 ÷ 90 = 0.10, or 10%. Choice B divides by the food eaten instead of the food absorbed (9 ÷ 110 ≈ 8%). Choice C is the share used for energy. Choice D is the droppings divided by the food eaten (20 ÷ 110 ≈ 18%).
Question 11 of 20 · Multiple Choice
Which observation is the best evidence that energy is released when cells use food molecules?
Answer: C
A body that stays warmer than the room is releasing energy from food molecules all the time. Choice A is water leaving bread, not a reaction in cells. Choice B compares masses, not energy. Choice D is breaking apart in digestion, which releases little energy compared with the reactions in cells.
Question 12 of 20 · Multiple Choice
Before migrating, a songbird eats many seeds, and its cells join small molecules from its blood into body fat. Which part of the model is this?
Answer: D
Joining small molecules into a new large molecule (fat) is putting back together, the same step that builds body protein. Choice A is digestion, which came earlier. Choice B would use the molecules up with oxygen instead of storing them. Choice C is about food that was never absorbed.
Question 13 of 20 · Multiple Choice
In Diagram 1, which step shows the "putting back together" part of the model?
Answer: A
Putting back together means joining small molecules into new large molecules, which happens in cells for growth and repair (Box 4a). Box 2 is breaking apart. Box 3 only moves molecules, and the waste arrow carries undigested food out.
Question 14 of 20 · Multiple Choice
Why must large food molecules such as starch and proteins be broken apart before body cells can use them?
Answer: B
Only small molecules can pass through the wall of the intestine into the blood and into cells. Choice A is false: large molecules are made of atoms. Choice C is false: the energy is released later, when cells react sugar with oxygen. Choice D names a substance the body takes in from the air.
Question 15 of 20 · Short Answer
Draw or describe a model that shows how the protein in a bean burrito could become part of a new fingernail. Include at least three steps.
Model answer: (1) Digestion breaks the bean protein apart into amino acids. (2) The blood carries the amino acids to cells at the base of the nail. (3) Those cells join the amino acids in a new order to make nail protein. Full credit names both breaking apart and putting back together, and shows that the nail protein is a different molecule from the bean protein.
Question 16 of 20 · Short Answer
A puppy eats 250 g of dry food in a day (invented data). 50 g leaves as droppings, and its body gains 30 g of new dry material. How many grams of the food were used to release energy? Show your work.
250 - 50 = 200 g absorbed; 200 - 30 = 170 g used to release energy. The atoms of those 170 g leave mostly as carbon dioxide and water.
Question 17 of 20 · Short Answer
A student's model shows the sugar from an apple going straight from the stomach into a leg muscle, where it stays as sugar forever. Name two things the model is missing.
Any two of: the blood carrying sugar from the digestive system to the muscle cells; the reaction of sugar with oxygen in the cells; the energy released for motion and warmth; the new molecules (carbon dioxide and water) that form; the carbon dioxide being breathed out. Full credit names two and explains that the sugar does not stay unchanged.
Question 18 of 20 · Short Answer
A student's paper clip model starts with 22 clips. At the end, the student counts 19 clips in the body and breath boxes and says the other 3 "were used up for energy." What is wrong with this model, and how should it be fixed?
Clips stand for matter, and matter is not used up: atoms are rearranged, not destroyed, while energy is released. The 3 missing clips must be found and placed somewhere real, such as the droppings or urine, or the student must recount. Full credit says the totals must match and that energy is shown by the tally marks, not by removing clips.
Question 19 of 20 · Short Answer
Two invented snack labels: Snack X has carbohydrate 20 g, protein 1 g and fat 8 g. Snack Y has carbohydrate 35 g, protein 2 g and fat 0 g. Using 4, 4 and 9 Calories per gram, which snack can release more energy? Show your work.
Snack X: 20 × 4 + 1 × 4 + 8 × 9 = 80 + 4 + 72 = 156 Calories. Snack Y: 35 × 4 + 2 × 4 = 140 + 8 = 148 Calories. Snack X releases more energy, even though it has less carbohydrate, because each gram of fat releases more than twice as much energy as a gram of carbohydrate.
Question 20 of 20 · Short Answer
During a race, a runner breathes faster and harder. Use the model to explain why.
The leg muscle cells are releasing more energy, so more sugar molecules react with oxygen. Faster breathing brings in more oxygen for those reactions and gets rid of the extra carbon dioxide they make. Full credit links breathing to both oxygen in and carbon dioxide out.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-LS1-7 mean?
MS-LS1-7 asks middle school students to develop a model of how food is broken apart and put back together into new molecules inside an organism. The new molecules build the body or react to release energy. The code means Middle School, Life Science, core idea 1 (From Molecules to Organisms), performance expectation 7.
Do students need to know the chemical equation for respiration in MS-LS1-7?
No. The Assessment Boundary says: "Assessment does not include details of the chemical reactions for photosynthesis or respiration." Students describe the reactions in words and models: sugar and oxygen form carbon dioxide and water and release energy. The balanced equation is part of high school biology (beyond this standard).
Does food turn into energy?
No, and this is a key idea of the lesson. Food is matter, and its atoms stay matter. In cells, the atoms are rearranged into new molecules, and those reactions release energy. Saying "food turns into energy" hides where the atoms go: mostly into carbon dioxide and water that leave the body.
What is the difference between digestion and what happens in cells?
Digestion breaks large food molecules into small ones in the digestive system. Cells then do something with those small molecules: they join them into new large molecules for growth and repair, or they react them with oxygen to release energy. A good model shows both stages.
How can a model show molecules without drawing atoms?
Use one object for each building block: a paper clip or bead for each sugar unit or amino acid. Hooked or strung objects stand for a large molecule, and separate objects stand for small molecules. Students should be able to say what each part of the model stands for and what the model leaves out.
Is MS-LS1-7 about the digestive system?
Only partly. The digestive system is where breaking apart happens, but MS-LS1-7 follows the matter further: into cells, into new molecules and out of the body. How the organs of the body work together is the focus of MS-LS1-3, a parallel standard.
Why do growing animals use most of their food for energy, not growth?
Cells release energy all the time to move, keep warm and do their work, so much of the absorbed food reacts with oxygen. Only a small share is joined into new body material. In this lesson's invented rat data, the share used for growth falls to zero once the rat reaches adult size.
Why does breathing matter for MS-LS1-7?
Breathing brings in the oxygen that reacts with sugar in cells, and it carries out the carbon dioxide those reactions make. It is the main way the atoms of food used for energy leave the body.
Can the lesson use real food in class?
This page uses paper food labels and models only, so no one eats or handles food. That avoids allergy risks and keeps the focus on the model. Paper clips, beads and drawings work well for the breaking-apart and putting-back-together steps.
What comes after MS-LS1-7 in high school?
In high school, HS-LS1-6 explains how atoms from sugar combine with other elements to form amino acids and other large molecules, and HS-LS1-7 models cellular respiration as bonds breaking and forming with a net release of energy. Those standards add the chemical details that MS-LS1-7 leaves out.
07
Related Standards
6 standards
These standards connect to MS-LS1-7: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
5-PS3-1Prerequisite
Model that energy in animals' food, used for growth and warmth, came from the sun
Lesson coming soon
MS-PS1-5Prerequisite
Model why atoms are conserved, so mass is conserved, in a chemical reaction
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