The branch of the U.S. government that is composed of the president and all the individuals, agencies, and departments that report to the president, and that is responsible for administering and enforcing the laws that Congress passes.
Proteins are biological polymers composed of amino acids. Amino acids, linked together by peptide bonds, form a polypeptide chain. One or more polypeptide chains twisted into a 3-D shape form a protein. Proteins have complex shapes that include various folds, loops, and curves.
Amino acids are joined together in proteins by peptide bonds. A peptide bond forms between the carboxyl group of one amino acid (amino acid 1 in the figure below) and the amino group of the adjacent amino acid (amino acid 2).