BackL4 Microbial Metabolism: Fundamentals, Energy, and Electron Transfer
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Microbial Metabolism
Introduction to Microbial Metabolism
Microbial metabolism encompasses the chemical processes that occur within microbial cells, including energy production, electron transfer, fermentation, respiration, glycolysis, the citric acid cycle, and oxidative phosphorylation. These processes are essential for cell growth, maintenance, and reproduction.
Fundamentals of Metabolism
Definition of Metabolism
Metabolism: The sum total of all chemical reactions that occur within a cell.
Types of Metabolic Reactions
Catabolic reactions (catabolism): Energy-releasing metabolic reactions that break down molecules into smaller units.
Anabolic reactions (anabolism): Energy-using metabolic reactions that build complex molecules from simpler ones.
Metabolic Types Based on Energy Sources
Classification of Microorganisms by Energy Source
Microorganisms are classified based on their energy sources, which can be chemical compounds or light.
Energy Source | Type | Example Organism | Representative Reaction |
|---|---|---|---|
Organic Chemicals | Chemoorganotrophs | Escherichia coli | Glucose + 6 O2 → 6 CO2 + 6 H2O |
Inorganic Chemicals | Chemolithotrophs | Thiobacillus thiooxidans | HS- + ½ O2 → S0 + H2O |
Light | Phototrophs | Rhodobacter capsulatus | Light energy conversion |
Defining the Requirements of Life
Energy from Redox Reactions
Microbial cells obtain energy from oxidation-reduction (redox) reactions, which are used to synthesize energy-rich compounds such as ATP. Redox reactions occur in pairs, known as half-reactions.
Electron donor: The substance oxidized in a redox reaction.
Electron acceptor: The substance reduced in a redox reaction.
Energy in Biological Systems
Measurement and Free Energy
Energy is measured in kilojoules (kJ), representing heat energy.
In any chemical reaction, some energy is lost as heat.
Free energy (G): The energy released that is available to do work.
The change in free energy during a reaction is referred to as ΔG0'.
Example Equation
The oxidation of glucose in aerobic respiration:
This reaction involves the transfer of electrons from glucose (electron donor) to oxygen (electron acceptor), releasing energy.
Electron Donors and Electron Acceptors
Redox Couples and Electron Carriers
Redox couples are arranged from strongest electron donor to strongest acceptor.
Redox reactions usually involve electron carriers as intermediates.
Electron carriers are divided into two classes:
Prosthetic groups: Attached to enzymes.
Coenzymes: Diffusible molecules, such as NAD+ and NADP.
Role of Electron Carriers
Electron carriers facilitate the transfer of electrons during metabolic reactions, enabling the conservation and utilization of energy within the cell.
Summary Table: Key Terms and Definitions
Term | Definition |
|---|---|
Metabolism | All chemical reactions in a cell |
Catabolism | Energy-releasing breakdown reactions |
Anabolism | Energy-consuming biosynthetic reactions |
Electron Donor | Substance oxidized in redox reaction |
Electron Acceptor | Substance reduced in redox reaction |
ATP | Primary energy currency of the cell |
Electron Carrier | Molecule that transfers electrons (e.g., NAD+) |
Additional info: The study notes expand on the brief points in the slides, providing definitions, examples, and context for key metabolic processes in microbial cells. The tables summarize classifications and terminology for clarity.
