Steric hindrance refers to the prevention of chemical reactions due to the physical size of atoms or groups within a molecule. When larger atoms or bulky groups are present, they can obstruct the approach of reactants, making it difficult for them to interact effectively. This phenomenon is significant in organic chemistry, influencing reaction rates and mechanisms. In addition to affecting reactions, steric hindrance plays a crucial role in determining the shape and stability of molecules. For example, in proteins, the arrangement of amino acids can create steric hindrance that affects how the protein folds and functions.