If noncovalent interactions such as hydrogen bonds are so we

If noncovalent interactions such as hydrogen bonds are so weak , how are they able to hold molecules in a particular conformation and hold two molecules (such as enzyme and substrate) together?

Solution

The non-covalent interactions are weak forces like hydrogen bonds, hydrophobic interactions, electrostatic interactions, and Vander Waals forces. Conformations in the structure of proteins at secondary and tertiary level are due to extensive hydrogen bonding. Though individually weak, these non-covalent interactions are able to hold molecules in a particular conformation because, they occur in large numbers. When a substrate binds to an enzyme, the attractive forces between the substrate and the enzyme alter the enzyme\'s conformation. As the substrate approaches the active site, these non-covalent interactions cause the active site to bend into such a shape that the substrate molecule closely fits into it. As the shape of the active site changes, it produces changes in the shape of other regions of the enzyme molecule altering the overall conformation of the enzyme. The conformational change in the enzyme allows the formation of more non-covalent interactions, which hold the two molecules together.