Metabolism and Energy Transformation Notes

Introduction to Metabolism

  • Metabolism is the sum of all chemical reactions in a living organism.
  • It can be divided into:
    • Anabolic pathways: consume energy to build complex molecules (e.g., protein synthesis).
    • Catabolic pathways: release energy by breaking down complex molecules (e.g., cellular respiration).

Forms of Energy

  • Energy: the capacity to cause change and exists in various forms:
    • Kinetic energy: associated with motion.
    • Heat (thermal energy): kinetic energy related to random movement of atoms/molecules.
    • Potential energy: energy due to an object's location or structure.
    • Chemical energy: potential energy available in chemical bonds, released during reactions.
  • Energy can be converted from one form to another.

Laws of Energy Transformation

  • Thermodynamics: the study of energy transformations.
  • Closed system: isolates itself from surroundings (e.g., liquid in a thermos).
  • Open system: allows transfer of energy and matter with surroundings (e.g., organisms).

First Law of Thermodynamics

  • Energy is constant (Law of energy conservation): cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

  • Every energy transformation increases the universe's entropy (disorder).
  • While order can decrease in a local system (organisms), the total entropy of the universe increases.

Free-Energy Change (∆G)

  • Free energy in living systems determines spontaneity:
    • The change in free energy (∆G) is calculated as:
      (∆G=∆H−T∆S)(∆G = ∆H - T∆S)
  • Reactions with a negative ∆G are spontaneous (exergonic).

ATP and Energy Coupling

  • ATP (Adenosine Triphosphate): main energy carrier in cells, composed of ribose, adenine, and three phosphate groups.
  • Energy coupling: ATP enables endergonic reactions to occur by coupling them with exergonic processes.
  • ATP can create energy from catabolic reactions.

Enzymes & Metabolic Reactions

  • Enzymes: catalytic proteins that speed up reactions by lowering activation energy.
  • Example: Sucrase hydrolyzes sucrose into glucose and fructose.

Factors Affecting Enzyme Activity

  • Each enzyme has optimal temperature and pH for functioning.
  • Cofactors: nonprotein helpers required for enzyme activity (can be inorganic or organic - coenzymes like vitamins).

Enzyme Inhibition

  • Competitive inhibitors: compete for the active site on the enzyme.
  • Noncompetitive inhibitors: bind elsewhere, altering enzyme shape and activity.

Regulation of Enzyme Activity

  • Regulation prevents chemical chaos by controlling metabolic pathways:
    • Allosteric regulation: changes enzyme shape and activity through bind at non-active sites.
    • Cooperativity: a form of allosteric regulation amplifying enzyme activity through favorable conformational changes.

Identifying Allosteric Regulators

  • Allosteric regulators can be potential drug candidates for controlling enzymatic activity.

Specific Localization of Enzymes in Cells

  • Organelles help bring order to metabolic pathways; enzymes can be found in specific locations, like mitochondria for respiration.

Gibbs Free Energy

  • Exergonic Reaction: (∆G < 0)
    • Reaction is spontaneous and energy is released.
  • Endergonic Reaction: (∆G > 0)
    • Reaction is non-spontaneous and energy is absorbed.

Summary of Key Points

  • Metabolic pathways consist of all chemical reactions.
  • Enzymes regulate reactions, and their activity is highly influenced by temperature, pH, and the presence of cofactors or inhibitors.
  • Thermodynamic laws dictate the flow and transformation of energy in biological systems.