Essential Knowledge 4.B.1

Interactions between molecules affect their structure and function.

Change in the structure of a molecular system may result in a change of the function of the system. [See also 3.D.3]

The shape of enzymes, active sites and interaction with specific molecules are essential for basic functioning of the enzyme. For an enzyme-mediated chemical reaction to occur, the substrate must be complementary to the surface properties (shape and charge) of the active site. In

other words, the substrate must fit into the enzyme’s active site. Cofactors and coenzymes affect enzyme function; this interaction relates to

a structural change that alters the activity rate of the enzyme. The enzyme may only become active when all the appropriate cofactors or coenzymes are present and bind to the appropriate sites on the enzyme.

Other molecules and the environment in which the enzyme acts can enhance or inhibit enzyme activity. Molecules can bind reversibly or irreversibly to the active or allosteric sites, changing the activity of the enzyme.

The change in function of an enzyme can be interpreted from data regarding the concentrations of product or substrate as a function of time. These representations demonstrate the relationship between an enzyme’s activity, the disappearance of substrate, and/or presence of a competitive inhibitor.

Students should be able to:

LO 4.17 analyze data to identify how molecular interactions affect structure and function.