Proteins are large, complex molecules made up of long chains of amino acids. These chains are folded and twisted into specific three-dimensional shapes, which determine their function.

Here's why other options are incorrect:

* Carbohydrates: Made up of sugars and starches, not amino acids.

* Lipids (fats): Made up of glycerol and fatty acids, not amino acids.

* Nucleic acids (DNA and RNA): Made up of nucleotides, not amino acids.