Filler note — a starting point for the notebook, to be replaced or expanded later.
What is protein?
Proteins are molecules made from chains of amino acids. The order of those amino acids helps determine a protein’s shape and function. They do many different jobs: enzymes help chemical reactions happen, antibodies help defend the body, and structural proteins support cells and tissues. MedlinePlus explains these roles.
So “protein” is both a category of molecules and a nutrient discussed on food labels. Keeping those two meanings in mind makes the topic easier to follow. A useful question to explore next: how does the body turn the amino acids from a meal into the particular proteins it needs?
From food to amino acids
Digestion breaks dietary protein down into amino acids. The body uses these to maintain and repair cells and make new ones. Some amino acids must come from food because the body cannot make them. Source: MedlinePlus, Protein in diet.
Protein comes from many foods, including animal and plant sources:
| Food group | Examples |
|---|---|
| Beans and soy foods | Lentils, beans, tofu, tempeh |
| Nuts and seeds | Peanuts, almonds, sunflower seeds |
| Animal foods | Eggs, dairy, fish, poultry |
These examples come from the MedlinePlus overview of dietary protein. The table lists sources, not equivalent portions or protein amounts.
Questions for a longer note
- How do protein needs change with age and activity?
- What does “protein quality” measure?
- How can food labels help compare protein per serving?
- What makes a protein habit practical over time?
Those questions can become the next version of this note, with more careful reading and examples.