There are 20 different types of amino acids that are commonly found in proteins. These amino acids can be combined in countless ways to form a vast array of proteins with different structures and functions.

Here's a breakdown:

* Amino acids: These are the building blocks of proteins. Each amino acid has a central carbon atom bonded to:

* An amino group (-NH2)

* A carboxyl group (-COOH)

* A hydrogen atom (-H)

* A side chain (R group) which varies between the 20 different amino acids.

* Peptide bonds: Amino acids are linked together by peptide bonds, which are formed between the carboxyl group of one amino acid and the amino group of another.

* Polypeptide chains: A chain of amino acids linked together by peptide bonds is called a polypeptide chain.

* Protein structure: The final three-dimensional structure of a protein is determined by the sequence of amino acids in its polypeptide chain, as well as interactions between the amino acids. This structure dictates the protein's function.

Let me know if you'd like to know more about the different types of amino acids or protein structure!