Monday
Monday: Where Does a Sandwich Go?
Rocket arrives at the Windowsill holding his lunch plate and frowning at it. "Bread, lettuce, tomato," he says. "By tonight it will all be gone. Where does it go?"
Raven points at his arm. "Some of it becomes you. What do you notice about how you have grown since spring?"
"My sleeves are short," Rocket admits. "So my arm is made of old sandwiches?"
Nova hovers over the plate, her cyan light tracing the bread. "Not sandwiches," she says. "Something much smaller. Think about what a loaf is built from."
"Flour, water, yeast," Rocket says. "And flour comes from wheat seeds. So, plant molecules?"
Raven grins. "Molecules go in. Molecules get taken apart. New molecules get built. That is this week."
Food is made of molecules
Everything you eat is made of molecules, groups of atoms joined together. The food you eat consists mostly of protein, fat and complex carbohydrates.
Those molecules are large. Your cells cannot use them as they are. They need smaller pieces: amino acids, fat molecules and simple sugars.
Turning food into those small pieces is a multistep process called digestion. It happens by physical means, such as chewing, and by chemical means.
Chemical digestion is a series of chemical reactions. In each one, a large molecule is broken apart into smaller molecules.
Then your body does something remarkable. It puts the pieces back together into new molecules, the ones your own cells are built from.
| Nutrient in food | Broken down into | What the body does with it |
|---|---|---|
| Carbohydrates (sugars and starches) | Glucose, a simple sugar | Breaks it down further to release energy |
| Proteins | Amino acids | Links them into the body's own proteins |
| Fats | Fatty acids | Builds cell membranes, stores energy |
- Read the question.
- Tap your answer.
The big idea of the week
Scientists describe it this way. Food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules.
Those new molecules support growth, or they release energy. Both happen in you every day.
Here is the surprising part. No atoms disappear. Atoms are conserved in chemical reactions, so they are only rearranged.
The atoms that were in your breakfast are still somewhere. Some are now part of you. Some left as carbon dioxide and water.
| Statement | True or false? |
|---|---|
| Food molecules are broken apart and then put back together into new molecules. | ? |
| Cells can use large food molecules just as they are. | ? |
| Atoms disappear during digestion. | ? |
| Food molecules can support growth or release energy. | ? |
Write the three numbers in your Windowsill Log. Those are the three big kinds of molecules you just read about.
Do not open or taste anything. This is a reading task.
Nothing is tasted or eaten during the labs. Food labels are read, not opened.
The facts come from the National Library of Medicine's medical encyclopedia, medlineplus.gov, and the free textbook Concepts of Biology.
Good start. Tomorrow you follow a bite through the digestive system and meet the organs that take it apart.