Enzymes and Oxidation in Biology

Lettuce Oxidation

• Cutting lettuce with a sharp knife exposes it to more air, leading to oxidation.
• Oxidation causes lettuce to taste bitter and wilt faster.
• Tearing lettuce minimizes air exposure and reduces oxidation.

Enzyme Objectives

• Describe enzyme components.
• Determine how pH, temperature, and substrate affect enzyme activity.
• Explain oxidation-reduction reactions.

Enzymes: Master Chefs of the Cell

• Enzymes speed up chemical reactions.
• They create a "workspace" where molecules interact more easily.

What are Enzymes?

• Enzymes are biological catalysts.
• They accelerate chemical reactions in cells without being consumed.
• Thousands of different enzymes exist, each catalyzing a specific reaction.
• Cells create enzymes based on genetic instructions.

Enzymes: A Catalyst

• Enzymes are catalysts that speed up reactions.
• They are not consumed in the reaction.
• Substrates bind to the active site.
• Bonds in the substrate weaken.
• Products are released.

Enzyme Components

• Holoenzymes consist of an apoenzyme (protein) portion.
• Cofactors are non-protein components.
• Metal ions (e.g., Fe, Cu, Mg, Mn, Ca, Co)
• Coenzymes (e.g., NAD+, NADP+, FMN, FAD).
• Active site is the enzyme region for substrate binding.

Factors Affecting Enzyme Activity

• Temperature: Increased temperature increases product formation but also increases vibrational energy that can disrupt bonds in the enzyme, reducing activity.
• pH: Changes in pH can interfere with enzyme bonds, affecting activity.
• Substrate Concentration: Higher substrate concentration increases reaction rate up to a threshold.
• Redox: Reduction-oxidation reactions affect enzyme activity.

Effects of High Heat on Enzymes

• High heat denatures enzymes.
• Hydrogen and ionic bonds in the enzyme are broken, changing its shape.
• Enzymes lose activity, and can no longer bind to substrates.
• Enzymes are degraded/denatured.

Extreme pH and Enzymes

• Extreme pH values can cause enzyme denaturation.

Oxidation-Reduction Reactions

• Oxidation involves losing electrons; reduction is gaining electrons.
• Redox reactions are electron transfers between molecules.

Redox Reactions in Cells

• Redox reactions transfer energy between molecules.
• NAD+ accepts two electrons and one proton to become NADH.
• NADH is a vital electron carrier in cellular respiration.

Real-World Examples of Redox Reactions

• Cellular respiration: Enzymes help transfer electrons in glucose breakdown for energy.
• Antioxidant enzymes: Protect cells from damage by free radicals using redox reactions.
• Immune system: Redox reactions are involved in fighting infections, producing nitric oxide to regulate responses.

The Big Picture of Redox

• Redox reactions are essential for life's processes; including energy production, cell signaling, and immune responses.

Enzyme Recap

• Enzymes are biological catalysts.
• Two enzyme interaction models are Lock and Key, and Induced Fit.
• Factors affecting enzyme activity include temperature, pH, substrate concentration and redox reactions.

This quiz explores the role of enzymes as biological catalysts, their mechanics, and how factors like pH and temperature influence their activity. Additionally, it covers oxidation processes, specifically how cutting lettuce can lead to bitter flavors and wilting due to increased oxidation. Test your understanding of these essential biochemical concepts.