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.
More specifically, peptide bonds join the carboxyl group of one amino acid with the amino group of another. For example, the amino acid called glycine can bond with the amino acid called alanine to form a dipeptide. The prefix 'di' means two, so, a dipeptide is defined as a compound consisting of two amino acids.