MS-LS1-7: How the Body Rebuilds Food into New Molecules
Also called NGSS MS-LS1-7 · Topic: Matter and Energy in Organisms and Ecosystems · Life Science
The Official Wording
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.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What MS-LS1-7 Means in Plain English
Middle schoolers build a model that follows food through the body. Big food molecules like starch and protein get split into small building blocks, which travel in the blood to cells. Cells snap those blocks together into new molecules for growth, or break them down further to release energy.
Students do not need the chemical equations for photosynthesis or cellular respiration. The idea is that atoms get rearranged, never created or destroyed. This builds on how plants make food (MS-LS1-6) and leads to how matter cycles through whole ecosystems (MS-LS2-3).
MS-LS1-7 I Can Statements
- I can model how food molecules are split into smaller building blocks.
- I can explain how cells reuse those blocks to build new molecules.
- I can show that breaking food down releases energy the body uses.
MS-LS1-7 Worked Example
A paper chain model of one meal, built with construction paper strips and tape.
Where do the atoms in a bowl of rice and beans end up after you eat it?
Set It Up: Construction paper strips in four colors, tape, three cups labeled gut, blood and muscle cell, and a cup of paper tokens for energy.
- Tape 12 yellow links into a long starch chain and 10 mixed-color links into a bean protein chain.Food: 2 big chains, 22 links
- Digest the meal by tearing both chains apart into single links in the gut cup.22 single links, none lost
- Move the single links in the blood cup over to the muscle cell.Small pieces travel, big chains cannot
- Retape the protein links in a new order to make a muscle protein.Same links, new order, new molecule
- Tear 6 yellow links in half and take one energy token for each.6 tokens: energy released
- Count every piece on the table.All 22 links accounted for
Every link from the meal ended up in a new molecule or in the pieces left after releasing energy.
Why it works: Digestion splits food into building blocks that cells rearrange into their own molecules, and breaking sugar apart releases stored energy.
Common Mistakes with MS-LS1-7
Thinking food disappears
“The body uses up the food, so it is gone.”
Try this: Follow the atoms. They are rearranged into body parts or leave as carbon dioxide and water, but they never vanish.
Mixing up matter and energy
“The food turns into energy.”
Try this: Energy is released when molecules break apart, but the atoms stay matter. Track the atoms and the energy separately in your model.
Skipping the rebuilding step
A model that ends when the food is torn apart
Try this: Show cells joining the building blocks into new molecules, because that rebuilding is how a body grows and repairs itself.
Where MS-LS1-7 Fits
Practice MS-LS1-7
Quick Check
- Why must starch be broken down before it reaches your cells?
- What two things can a cell do with the building blocks from food?
- If you eat 500 grams of food, why don't you gain 500 grams?