BIOL 112: Energy, Enzymes, and Metabolism

Exam III Overview

  • Scheduled in about 3 weeks
  • Key topics covered in the exam:
    • Energy, Enzymes, and RedOx-Reaction
    • Focus on calculating redox reactions
    • Metabolism
    • Topics include respiration and the Krebs Cycle
    • Fundamental Genetics
    • Including Mendelian genetics and more

BIOL 112

Energy and Enzymes: An Introduction to Metabolism

  • Instructor: Dr. Thomas Mueller

Fundamental Concepts of Energy

  • E=mc²:

    • Fundamental equation illustrating the interchangeability of energy and mass.
    • Energy can exist as electromagnetic radiation, traveling at the speed of light.
    • Key Concept: Everything in the universe is a form of energy.

  • Law of Conservation of Energy:

    • The amount of energy in the universe is constant: energy cannot be created or destroyed (First Law of Thermodynamics).

  • Second Law of Thermodynamics:

    • In a closed system, the amount of entropy (disorder) tends to increase, indicating energy transformations lead to increased disorder.
    • Thermodynamics is the study of energy, heat, and the capacity of energy to do work.

Energy Definitions

  • Energy: The capacity to produce work or heat.
  • Heat (q): The lowest form of energy, often released in exothermic reactions, such as combustion.
Exothermic Reactions
  • Exothermic reaction: Energy is released, frequently in the form of heat.
    • Example: Combustion of substances with oxygen produces energy, heat, and light.
    • Thermite Reaction Example:
    • Chemical Reaction: [ ext{Fe}2 ext{O}3 + 2 ext{Al}
      ightarrow 2 ext{Fe} + ext{Al}2 ext{O}3 ]

Redox Reactions

  • Definition: Redox (reduction-oxidation) reactions involve the transfer of electrons between substances.
  • Key Terms:
    • Oxidized Substance: Loses electrons.
    • Reduced Substance: Gains electrons.
Oxidation Numbers Calculation

  • Rules:

    1. Free elements have an oxidation state of zero.
    2. For ions, the oxidation number equals the ion charge.
    3. Oxygen generally has an oxidation number of -2; peroxides have an oxidation number of -1.
    4. Hydrogen is +1 when bound to non-metals, -1 when bound to metals.
    5. In neutral compounds, the sum of oxidation states is zero or equals the charge in ions.

  • Examples of Calculating Oxidation Numbers:

    1. [ 2 ext{Fe} + ext{O}2 ightarrow ext{Fe}2 ext{O}_3 ]
    2. [ 2 ext{KI} + ext{H}2 ext{O}2
      ightarrow ext{I}_2 + 2 ext{KOH} ]
    3. [ 2 ext{FeCl}3 + ext{H}2
      ightarrow 2 ext{FeCl}_2 + 2 ext{HCl} ]
    4. [ 2 ext{NaBr} + ext{Cl}2 ightarrow 2 ext{NaCl} + ext{Br}2 ]

Enzymes: Key to Cellular Activity

  • Enzymes are critical as they:
    • Enable cellular activities by catalyzing chemical reactions.
    • Allow cells to acquire and use energy.
Types of Energy
  • Kinetic Energy: Energy of motion.
    • Example: Thermal energy is the energy of moving molecules.
  • Potential Energy: Stored energy based on position or configuration.
    • Example: Chemical energy is stored in chemical bonds.

Chemical Reactions and Energy Transformations

  • First Law of Thermodynamics: Energy is conserved and can only be transferred and transformed.
  • Understanding Energy Transformations:
    • A chemical reaction can lead to changes in potential energy based on bonds involved.
    • If products possess shorter, stronger bonds than the reactants, potential energy decreases.
  • Example: Isooctane combustion:
    [ ext{C}8 ext{H}{18} + 12.5 ext{O}2 ightarrow 8 ext{CO}2 + 9 ext{H}_2 ext{O} + ext{Energy} ]
Enthalpy (H)
  • Definition: Total energy within a molecule.
  • Enthalpy change (ΔH) metrics:
    • ΔH < 0: Products have lower potential energy than reactants (exothermic).
    • ΔH > 0: Products have higher potential energy (endothermic).
Entropy (S)
  • Definition: A measure of disorder within a system.
  • Principle: Entropy tends to increase during energy transformations.

Gibbs Free Energy (G)

  • Gibbs free energy helps predict spontaneity of reactions:
    • Equation: [ ext{ΔG} = ext{ΔH} - T ext{ΔS} ] wherein:
    • ΔH = Change in enthalpy
    • ΔS = Change in entropy
    • T = Temperature in Kelvin
  • Reactions and Gibbs Free Energy:
    • ΔG < 0: Reaction is spontaneous (exergonic).
    • ΔG > 0: Reaction is non-spontaneous (endergonic).
    • ΔG = 0: Reaction is at equilibrium.

Temperature and Concentration's Effect on Reaction Rates

  • Chemical reactions require sufficient energy for bond-breaking and formation:
    • Higher temperatures and concentrations lead to increased collision frequency, enhancing reaction rates.
  • Collision Theory:
    • More frequent collisions between molecules increase reaction rates.
    • Specific orientation during collisions is critical.

Regulation of Reaction Rates and Enzymes

  • Nonspontaneous reactions may be driven by coupling them with spontaneous ones.
  • Redox reactions are essential in biology and for energy transfers.
Enzyme Function
  • Enzymes: Protein catalysts that lower activation energy, allowing faster reactions.
  • Enzymes have unique active sites, and substrate binding can lead to an induced fit, enhancing reactivity.
Factors Affecting Enzyme Function
  • Enzyme activity is influenced by:
    • Temperature and pH: Optimal conditions for enzyme activity exist and this varies by enzyme type.
  • Regulatory molecules can affect enzyme binding and activity:
    • Competitive inhibition blocks substrates from entering active sites,
    • Allosteric regulation changes enzyme shapes non-competitively.
Metabolic Pathways and Regulation
  • Metabolic pathways consist of a series of enzyme-catalyzed reactions.
  • Feedback inhibition: Final product inhibits an earlier reaction to prevent excess production.
  • Catabolic pathways break down substances for energy, whereas anabolic pathways synthesize molecules from smaller units, requiring energy.
Evolution of Metabolic Pathways
  • Pathways evolve through new enzyme recruitment and retro-evolution based on substrate availability, leading to complex biological processes.

Summary

  • Enzymes play a critical role not just in driving reactions, but also in ensuring that cellular functions are efficient and responsive to environmental changes. Understanding thermodynamics, free energy, and enzymatic mechanisms provides insight into biological processes at the molecular level.