Rocket has already made a paper chain two meters long and is waving it like a flag. "This is a protein!" he shouts.
"Careful," Raven laughs. "Before you tear it, count the links. What do you notice about the colors?"
Rocket counts. "Twenty links, five colors. Each color is a different amino acid?"
Nova circles the chain. "Now imagine you are the stomach," she says. "What happens to the chain?"
Rocket pulls the links apart until twenty loose rings lie on the table. Raven starts linking them into a new, different chain.
"Same rings, new order," she says. "Now breathe on this mirror and tell me what you see."
Today you build a model of what digestion does to a food molecule. Then you look for water that your own body is giving off.
A model is not the real thing. It helps you picture something too small to see. Scientists use models exactly this way.
| Measurement | My count or time | What it stands for |
|---|---|---|
| Links in the first chain | A large food molecule | |
| Loose rings after taking it apart | Small molecules after digestion | |
| Links in the new chains, total | New molecules the body built | |
| Fog on the mirror, seconds to clear (try 1) | Water leaving the body | |
| Fog on the mirror, seconds to clear (try 2) | Water leaving the body |
Your chain is a model of a large food molecule. Pulling it apart is digestion: chemical reactions break the molecule into small pieces.
Relinking the rings is what your body does next. It builds new molecules from the pieces, in its own order.
The number of rings did not change. In real chemical reactions, atoms are conserved too. They are rearranged, never lost.
Now the mirror. Water leaves the body as exhaled air, sweat and urine. The fog is some of that water landing on cool glass.
Where does that water come from? Some comes from what you drink. Some is made inside cells when they break glucose down with oxygen.
An open anatomy textbook gives the number: about 230 milliliters of water a day is made in the last steps of respiration.
| What the lab shows | True or false? |
|---|---|
| Taking the chain apart models chemical digestion. | ? |
| Some rings disappear when a chain is taken apart and rebuilt. | ? |
| The fog on the mirror is water leaving the body in exhaled air. | ? |
| Cells make some water when they break down glucose with oxygen. | ? |
Careful modeling. Tomorrow you read a real nutrition table and learn why one gram of fat holds more energy than one gram of sugar.