Bio111-Ch8.Stud.pptx

Chapter 8: An Introduction to Metabolism

The Energy of Life

  • Metabolism defined as the totality of chemical reactions in an organism.

  • Metabolic pathways: Specific series of steps altering a molecule to produce a product, each step influenced by a specific enzyme.

Metabolic Pathways

  • Catabolic Pathways:

    • Release energy by breaking down complex molecules into simpler compounds.

    • Described as "downhill" reactions.

  • Anabolic Pathways:

    • Consume energy to build complex molecules from simpler ones.

    • Described as "uphill" reactions.

  • Organisms utilize energy from catabolic reactions to power anabolic reactions.

Forms of Energy

  • Energy: Capacity to cause change and do work.

  • Bioenergetics: Study of energy flow through living organisms.

  • Various forms of energy:

    • Potential: Stored energy.

    • Kinetic: Energy of motion.

    • Thermal: Energy related to temperature.

Laws of Energy Transformation

  • Thermodynamics: Study of energy transformations.

  • Isolated System: No exchange of energy or matter (e.g., thermos).

  • Open System: Exchange of energy and matter occurs (e.g., organisms).

    • Absorb energy from light or food.

    • Release heat and metabolic wastes (like CO2).

The First Law of Thermodynamics

  • Energy in the universe is constant; can be transferred or transformed but not created or destroyed.

  • Also known as the principle of conservation of energy.

The Second Law of Thermodynamics

  • Energy transfer or transformation results in some energy being lost as heat, making it unavailable for work.

  • Entropy: Measure of molecular disorder increases with energy transformations.

Exergonic and Endergonic Reactions

  • Exergonic Reactions: Release free energy to the surroundings.

  • Endergonic Reactions: Absorb free energy from surroundings.

  • Importance in metabolism: Understanding energy changes in chemical reactions.

Equilibrium and Metabolism

  • Closed systems eventually reach equilibrium, causing no work.

  • Cells are open systems with constant material flow, preventing equilibrium.

ATP and Cellular Work

  • Energy Coupling: Using energy from exergonic processes to drive endergonic ones, primarily mediated by ATP.

  • ATP Hydrolysis: Essential for energy transfer in cells.

Enzymes and Metabolism

  • Enzymes: Macromolecules that catalyze reactions by lowering energy barriers without being consumed.

    • Example: Breakdown of glucose governed by enzymes.

  • Active site: Region where enzymes bind substrates, forming enzyme-substrate complexes for specific reactions.

Factors Affecting Enzyme Activity

  • Enzyme activity influenced by temperature and pH.

  • Chemicals may specifically inhibit or affect enzymes.

Enzyme Inhibitors

  • Competitive Inhibitors: Resemble substrate and bind at the active site.

  • Noncompetitive Inhibitors: Bind elsewhere, altering enzyme function.

  • Examples: Toxins, poisons, pesticides, antibiotics.

Regulation of Enzyme Activity

  • Metabolic pathways regulated by gene expression and enzyme activity.

  • Allosteric Regulation: Regulatory molecule affects protein function at different site.

  • Feedback Inhibition: End product of a pathway shuts down that pathway.

Localization of Enzymes

  • In eukaryotic cells, enzymes are often located in specific organelles (e.g., mitochondria for cellular respiration).

Conclusion

  • Understanding metabolism is essential for comprehending how living organisms transform energy and matter, and how enzymes play a crucial role in these processes.