[noun] Proteins form one of the three families of macronutrients (elements that provide the body with energy), the others being carbohydrates and lipids. They are present in all living cells and are made up of several chains of amino-acid residues linked by peptide bonds. They serve many functions within a cell or an organism:
- Structural function: renewal of muscle tissue and appendages (hair, nails, etc.).
- Enzymatic function: ensuring the chemical reactions of synthesis and degradation required for cell metabolism.
- Motor function: molecule transport within cells.