CH+5+Funke+Metabolism

Chapter Overview: Microbial Metabolism

Introduction to Energy

• Energy: The ability to perform work, often transferred in biological processes.

• Potential Energy: Stored energy, e.g., gravitational energy; available for work.

• Kinetic Energy: Energy of motion; e.g., muscle contractions.

Laws of Thermodynamics

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

Metabolism: The Big Picture

• Metabolism: Combination of all chemical reactions in an organism.

  • Catabolism: Breakdown of complex molecules, releasing energy (exergonic) and providing building blocks for anabolism.

  • Anabolism: Building complex molecules from simple ones, requiring energy (endergonic).

• Importance: Microbial metabolism can lead to diseases and spoilage but also beneficial pathways.

ATP: Energy Currency

• ATP Role: Acts as an energy intermediary between catabolism and anabolism.

• Metabolic Pathways: Sequences of enzymatically catalyzed reactions, determined by enzymes encoded by genes.

Catabolic and Anabolic Reactions

Definition and Roles

• Learning Objectives: Define metabolism, differentiate anabolic and catabolic reactions, and understand ATP's role.

• Energy Transfer: Energy from catabolism is used to synthesize ATP, which is then used for anabolic reactions.

Metabolic Pathways

• Enzyme involvement is crucial; metabolic pathways consist of sequences of reactions catalyzed by enzymes.

Enzymatic Reactions and Energy Activation

• Enzymes: Biological catalysts that speed up reactions without being altered.

• Factors Influencing Enzyme Activity: Temperature, pH, substrate concentration, and inhibitors.

  • Competitive inhibition: Competes with substrate for the active site.

  • Noncompetitive inhibition: Alters the active site indirectly.

  • Feedback inhibition: End-product inhibits an earlier step in the pathway.

Energy Production in Cells

Types of Reactions

• Oxidation-Reduction Reactions: Key reactions that involve electron transfer (OIL RIG: Oxidation Is Loss, Reduction Is Gain).

• Phosphorylation: Processes that generate ATP through substrate-level phosphorylation and oxidative phosphorylation.

Phosphorylation Processes

• Substrate-Level: Direct transfer of PO4- from a phosphorylated compound to ADP.

• Oxidative Phosphorylation: Involves an electron transport chain and chemiosmosis producing ATP.

Glycolysis and Krebs Cycle Overview

• Glycolysis: Breakdown of glucose to pyruvic acid, generating ATP and NADH.

• Krebs Cycle: Further breakdown of acetyl CoA producing electron carriers (NADH and FADH2).

Final Electron Acceptors in Respiration

• Aerobic Respiration: Uses oxygen (O2) as the final electron acceptor.

• Anaerobic Respiration: Uses a different molecule as a final electron acceptor, resulting in different products.

Fermentation Processes

• Types of Fermentation: Includes lactic acid and alcoholic fermentation, converting pyruvic acid into various end-products without using O2.

• Industrial Uses: Various fermentations are used to produce alcohol, vinegar, dairy products, and more.

Conclusion

• Integration of Metabolism: Metabolic pathways function simultaneously with common intermediates, demonstrating the interconnectedness of catabolism and anabolism.

• Metabolic Diversity: Different organisms exhibit varied nutritional patterns, using light (phototrophs) or organic/inorganic chemicals (chemotrophs) for energy.

Laws of Thermodynamics

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed from one form to another. This principle is fundamental in understanding how energy flows through biological systems.

• Second Law of Thermodynamics: In any energy transfer, the total entropy (disorder) of a closed system can only increase over time. This emphasizes the directionality of energy transformations and the inefficiency of energy use in biological processes, resulting in heat loss.

Metabolic Pathways

• Definition: Metabolic pathways are sequences of enzymatically catalyzed chemical reactions that occur within cells. They are organized into two types:

  • Catabolic Pathways: Involve the breakdown of complex molecules, releasing energy and providing building blocks for cellular processes (e.g., glycolysis and Krebs cycle).

  • Anabolic Pathways: Involve the synthesis of complex molecules from simpler ones, requiring energy inputs (e.g., protein synthesis).

• Importance: Metabolic pathways illustrate the interconnectedness of catabolism and anabolism, where products from one pathway may serve as substrates for another, reflecting the organism's energy management and resource utilization. Each pathway is tightly regulated by enzymes to respond to the cellular environment and energy status.