Science, Tech, Math › Science Types of Chemical Bonds in Proteins Share Flipboard Email Print Martin McCarthy/Getty Images Science Chemistry Biochemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 17, 2019 Proteins are biological polymers constructed from amino acids joined together to form peptides. These peptide subunits may bond with other peptides to form more complex structures. Multiple types of chemical bonds hold proteins together and bind them to other molecules. Take a closer look at the chemical bonds responsible for protein structure. Peptide Bonds The primary structure of a protein consists of amino acids chained to each other. Amino acids are joined by peptide bonds. A peptide bond is a type of covalent bond between the carboxyl group of one amino acid and the amino group of another amino acid. Amino acids themselves are made of atoms joined together by covalent bonds. Hydrogen Bonds The secondary structure describes the three-dimensional folding or coiling of a chain of amino acids (e.g., beta-pleated sheet, alpha helix). This three-dimensional shape is held in place by hydrogen bonds. A hydrogen bond is a dipole-dipole interaction between a hydrogen atom and an electronegative atom, such as nitrogen or oxygen. A single polypeptide chain may contain multiple alpha-helix and beta-pleated sheet regions. Each alpha-helix is stabilized by hydrogen bonding between the amine and carbonyl groups on the same polypeptide chain. The beta-pleated sheet is stabilized by hydrogen bonds between the amine groups of one polypeptide chain and carbonyl groups on a second adjacent chain. Hydrogen Bonds, Ionic Bonds, Disulfide Bridges While secondary structure describes the shape of chains of amino acids in space, tertiary structure is the overall shape assumed by the entire molecule, which may contain regions of both sheets and coils. If a protein consists of one polypeptide chain, a tertiary structure is the highest level of structure. Hydrogen bonding affects the tertiary structure of a protein. Also, the R-group of each amino acid may be either hydrophobic or hydrophilic. Hydrophobic and Hydrophilic Interactions Some proteins are made of subunits in which protein molecules bond together to form a larger unit. An example of such a protein is hemoglobin. Quaternary structure describes how the subunits fit together to form the larger molecule.