Proteins are made up of amino acids, which are the building blocks of life. Here are the atoms that make up amino acids:

* Carbon (C)

* Hydrogen (H)

* Oxygen (O)

* Nitrogen (N)

Sometimes you'll also find sulfur (S) in some amino acids, specifically cysteine and methionine.

Let's break it down further:

* Carbon (C): Forms the backbone of the amino acid structure.

* Hydrogen (H): Attached to the carbon backbone and the nitrogen of the amino group.

* Oxygen (O): Found in the carboxyl group (COOH) and sometimes in the side chains of certain amino acids.

* Nitrogen (N): Found in the amino group (NH2) and sometimes in the side chains of certain amino acids.

* Sulfur (S): Found in the side chains of cysteine and methionine.

So, while the primary building blocks are carbon, hydrogen, oxygen, and nitrogen, sulfur can also be present in some proteins.