Enzymes

Enzyme-Substrate Interactions

Flow Diagram for Enzyme-Substrate Reactions

  • Objective: Create a flow diagram to depict the interactions between the enzyme's active site and the substrate.

  • Focus: Understand the movement, interaction, and product synthesis in detail compared to previous years.

Physical Properties for Enzyme-Substrate Complex Formation

  • Enzyme Structure: Enzymes have a specific three-dimensional shape.

    • Complementary Shape: Similar to the complementary base pairing in DNA, the substrate shape is complementary to the active site.

  • Induced Fit Model:

    • Definition: The enzyme shifts its shape slightly to form a tighter bond with the substrate.

    • Metaphor: Compared to a hand fitting into a glove or mitten where the shape adjusts to ensure a strong fit.

Molecular Motion in Liquid State

  • Medium: Enzyme-substrate complexes predominantly form in a liquid state.

    • Characteristics of Liquid State:

    • Molecules touch each other without a fixed shape.

    • Particles in a liquid state have more energy than in solid form but less than in gases.

    • Implication for Enzyme Action: Increased molecular movement enables collisions between enzyme and substrate.

Orientation and Alignment of Molecules

  • Collision Dynamics: Collisions do not guarantee reactions; proper orientation is crucial for successful interactions.

  • Examples:

    • A substrate fitting into an active site that is facing the wrong direction will not react.

Factors Affecting Reaction Rates

  • Temperature: Higher temperatures increase kinetic energy, promoting more collisions.

  • Substrate Concentration: Increased number of substrates enhances the chances of enzyme interaction.

  • Enzyme Concentration: More enzymes lead to higher reaction rates.

  • Immobilization of Enzymes: Anchoring enzymes allows substrates to reach them more easily.

  • Compartmentalization: Smaller spaces increase collision rates due to reduced volume.

  • pH Levels: Ambient and appropriate pH levels are vital for maintaining enzyme activity.

Chemical Properties Influencing Binding

  • Attraction Mechanism: Opposite charges between substrate and active site lead to stronger interactions.

  • Molecular Motion: In aqueous solutions, substrates can move freely and collide with enzymes more efficiently.

Substrate Size and Enzyme Interaction

  • Most substrates are smaller than enzymes, which allows faster movement in solution.

  • Larger Substrates:

    • Examples include polypeptides and DNA, requiring enzymes to move towards them.

    • Enzymes can only bind to sections of larger biomolecules due to size constraints.

    • DNA Example: The enzyme binds to specific sections to catalyze the reaction without needing the whole molecule to fit into the active site.

Immobilized Enzymes in Processes

  • Example: Lactase is immobilized in milk production to break down lactose, demonstrating enzyme utility in food processing.

Specificity of Enzymes

  • Complete Specificity: Some enzymes, like glucokinase, have only one substrate they bind to.

  • Less Specific Enzymes:

    • Enzymes such as hexokinase can bind various hexagonal sugars (e.g., glucoses, galactoses).

    • Proteases can digest any polypeptides by targeting sections of the molecule, having a less stringent fit, leading to weaker binding.

Effects of Environmental Factors on Enzyme Activity

  • Denaturation: Changes in temperature, pH, and extreme conditions can cause enzymes to denature, altering their activity.