Which enzyme-substrate theory is considered outdated?

Which enzyme-substrate theory is considered outdated?

• A. Induced fit theory
• B. Lock and key model
• C. Transition state theory
• D. Catalysis theory

Answer: (B)

The concept being tested is how enzymes recognize and bind their substrates. The old lock-and-key idea suggests a rigid, preformed fit where the active site and substrate are perfectly complementary without any change. In reality, enzymes are flexible and often mold themselves around the substrate as it binds. This induced fit reshapes the active site to create a snug fit, stabilizes the transition state, and lowers the energy barrier for the reaction. Because of this dynamic behavior, the rigid lock-and-key picture is considered outdated. The induced fit view better explains specificity and catalytic efficiency, while other ideas like transition state theory describe the energetic basis of catalysis and remain central to how enzymes work.

The concept being tested is how enzymes recognize and bind their substrates. The old lock-and-key idea suggests a rigid, preformed fit where the active site and substrate are perfectly complementary without any change. In reality, enzymes are flexible and often mold themselves around the substrate as it binds. This induced fit reshapes the active site to create a snug fit, stabilizes the transition state, and lowers the energy barrier for the reaction. Because of this dynamic behavior, the rigid lock-and-key picture is considered outdated. The induced fit view better explains specificity and catalytic efficiency, while other ideas like transition state theory describe the energetic basis of catalysis and remain central to how enzymes work.