The statement given in the question is FALSE.
Protein molecules are made from amino acids. Structurally, an amino acid is made up of a carboxyl group, an amino group and a unique side group. The amino group of amino acid is composed on nitrogen linked to two hydrogen atoms. Generally, the nitrogen component of all proteins is between the range of 15% to 25%. The quantity of oxygen in proteins also falls within the same range. Thus, the percentage of nitrogen in proteins is not up to 50%.