Final answer:
Proteins have four levels of structure: primary, secondary, tertiary, and quaternary structure. They are held together by various chemical bonds and interactions, including peptide bonds, hydrogen bonding, ionic bonding, disulfide linkages, and dispersion forces.
Step-by-step explanation:
Protein Structure
Proteins have four levels of structure: primary, secondary, tertiary, and quaternary structure.
1. Primary structure: It refers to the specific sequence of amino acids in a protein's polypeptide chain, which is held together by peptide bonds.
2. Secondary structure: It includes local formations of regular structures like alpha-helices and beta-pleated sheets, stabilized by hydrogen bonding between amino acids.
3. Tertiary structure: It refers to the three-dimensional folding of a polypeptide chain, formed by interactions such as ionic bonding, hydrogen bonding, disulfide linkages, and dispersion forces.
4. Quaternary structure: It involves the arrangement of multiple polypeptide subunits to form a functional protein.
These different levels of protein structure are crucial for the protein's overall shape and its ability to perform specific functions.