Enzymes and the Active Site

Key Concepts

• Enzymes are biological molecules that act as catalysts, speeding up reactions by lowering activation energy.
• Enzymes are proteins made of long chains of amino acids folded into specific three-dimensional shapes.

Enzyme Structure

• Active site: Specific region where substrate molecules bind.
• Enzymes exhibit a high specificity for their substrate, often explained by the "lock and key" model or the "induced fit" model.

Mechanism

• Substrate: Molecule upon which an enzyme acts.
• Enzyme-substrate complex: Temporary complex formed when an enzyme binds to its substrate molecule(s).
• Activation energy (Ea): Energy required to start a reaction; enzymes lower this energy.

Models of Enzyme Action

• Lock and Key Model: The enzyme's active site is complementary in shape to the specific substrate, fitting together like a lock and key.
• Induced Fit Model: The enzyme's active site is flexible and can adjust its shape to fit the substrate.

Factors Affecting Enzyme Activity

• Temperature: Each enzyme has an optimal temperature at which it functions best.
• pH Levels: Each enzyme works best at a specific pH level, affected by the environment.
• Concentration: The concentration of both enzyme and substrate can affect the rate of reaction.

Enzyme Inhibition

• Competitive Inhibition: An inhibitor competes with the substrate for binding to the active site.
• Non-competitive Inhibition: An inhibitor binds to a site other than the active site, changing the enzyme's shape and function.

Summary

Enzymes play a crucial role in facilitating biological reactions. Understanding their structure and function is essential for comprehending their catalytic action and the various factors that can influence their activity.