4-MICROBIAL METABOLISM

Page 1: Introduction

• Microbial Metabolism

  • Presented by: Kimberley Reiser, PH.D.

  • Intended for exclusive use by BIO 214 NCC students.

Page 2: Carbohydrate Catabolism Overview

• Glucose as Starting Point

  • Primary substrate for metabolic pathways.

• Processes of Glucose Catabolism

  • Cellular respiration and fermentation.

• Immediate Benefit

  • ATP generation is crucial for energy in all cellular activities.

Page 3: ATP Functionality

• ATP Reaction

  • Reaction: ATP + H2O → ADP + Pi

  • Releases energy; represented as DG = -7.3 kcal/mol.

  • The negative sign signifies an exothermic reaction.

  • Notably, this reaction is reversible.

Page 4: Structure of Glucose

• Chemical Structure of Glucose

  • Linear and Ring Forms

    • Glucose can be represented in linear form.

    • Ring structure is commonly abbreviated.

Page 5: Overview of Respiration and Fermentation

• Key Processes in Cellular Metabolism

  • Glycolysis

    • Converts glucose into pyruvic acid, generating ATP and reducing NAD+ to NADH.

  • Krebs Cycle (Citric Acid Cycle)

    • Converts pyruvic acid to Acetyl CoA; produces ATP, NADH, and CO2.

  • Electron Transport Chain (ETC)

    • Uses electrons from NADH and FADH2 to produce a significant amount of ATP via oxidative phosphorylation.

    • Oxygen is the final electron acceptor in respiration, while fermentation does not utilize this mechanism.

Page 6: Fates of Pyruvic Acid

• Three Possible Pathways for Pyruvic Acid:

  • Aerobic respiration

  • Anaerobic respiration

  • Fermentation

Page 7: Aerobic Respiration Details

• Requirements and Products

  • Requires oxygen; completely breaks down glucose into CO2 and water.

  • Yields 38 molecules of ATP per glucose.

• Chemical Stages

  • 1. Glycolysis

  • 2. Krebs Cycle

  • 3. Electron Transport Chain (ETC)

Page 8: ATP Yield in Prokaryotic Aerobic Respiration

• Overview

  • Similar to Page 7 details: requiring oxygen, complete glucose breakdown, yielding 38 ATP.

• Chemical Stages Reinforced

  • Glycolysis, Krebs Cycle, Electron Transport Chain (ETC).

Page 9: Pathway Locations for Eukaryotes and Prokaryotes

• Glycolysis: Cytoplasm (both Eukaryotes and Prokaryotes)

• Intermediate Step: Cytoplasm (both Eukaryotes and Prokaryotes)

• Krebs Cycle: Mitochondrial matrix (Eukaryotes) / Cytoplasm (Prokaryotes)

• ETC: Mitochondrial inner membrane (Eukaryotes) / Plasma membrane (Prokaryotes)

Page 10: Summary of Respiration

• Aerobic Respiration

  • O2 is the final electron acceptor.

  • Yields maximum energy through complete oxidative pathways.

• Anaerobic Respiration

  • O2 is not the final acceptor, resulting in less energy yielded since Krebs cycle function is limited.

Page 11: Anaerobic Respiration Details

• Processes

  • Uses inorganic molecules as final electron acceptors, e.g.,

    • SO4^2- → H2S

    • NO3- → NO2-, N2O, N2

    • CO3^2- → CH4

  • Yields less energy compared to aerobic respiration.

• Stages: Glycolysis, Krebs Cycle, Electron Transport Chain.

Page 12: Electron Acceptors in Anaerobic Respiration

• Common Electron Acceptors and Products:

  • NO3– → NO2–, N2 + H2O

  • SO4– → H2S + H2O

  • CO3^2– → CH4 + H2O

Page 13: Fermentation Overview

• Scientific Definition

  • Energy release from oxidation of organic molecules without requiring oxygen.

• Mechanisms:

  • Does not involve Krebs cycle or ETC; uses organic molecules for final electron acceptance.

  • Generates minimal ATP.

Page 14: Glycolysis and Fermentation Pathways

• Pathways Summary

  • Glycolysis pathway divides into fermentation and respiration pathways.

  • Identifies products formed during fermentation from pyruvic acid.

Page 15: Fermentation Characteristics

• Fundamentals

  • No need for an external electron acceptor; organic end products are formed. Some have high commercial value: ethanol, lactic acid.

  • Only produces 2 ATP molecules.

  • Stages: Primarily Glycolysis with diverse post-glycolysis pathways.

Page 16: Comparative Pathways in Moon Formulas

• Visual Comparison

  • Various organisms and fermentation end-products mapped out with end-goals: ethanol, lactic acid, etc.

Page 17: Organismal Comparison of Fermentation End-products

• Microbial Fermentation Outputs

  • Lists different microbes with corresponding fermentation products:

    • Streptococcus, Lactobacillus, Bacillus: Lactic Acid

    • Saccharomyces: Ethanol and CO2

    • Other bacteria showcasing various by-products, including butyric acid.

Page 18: Industrial Uses of Fermentations

• Summary of Fermentations by Products

  • Lists microorganisms responsible for producing: ethanol, lactic acid, citric acid, etc., and their industrial applications based on starting materials.

Page 19: Comparative Process Table

• Comparison Table

  • Details ATP production, conditions, final electron acceptors, and types of phosphorylation across aerobic respiration, anaerobic respiration, and fermentation.

  • Emphasis on ATP yields; 36-38 ATP for aerobic, variable (usually >2) for anaerobic processes, and only 2 for fermentation.

Page 20: Nutritional Classification of Organisms

• Classifications Based on Energy and Carbon Sources

  • Chemotrophs vs phototrophs and their respective categories and characteristics, such as using light or chemicals for energy.

Page 21: Carbon Source Classification

• Categorization of Organisms

  • Autotrophs (inorganic carbon source) vs heterotrophs (organic molecule catabolizers)

Page 22: Organisms Based on Energy Source

• Energy Acquisition

  • Categorizes organisms by energy acquisition method: chemotrophs (chemical sources) and phototrophs (light sources).

Page 23: Overview of Energy and Carbon Source Categories

• Distinct Morphologies of Organisms

  • Lists various organisms based on their energy, carbon sources, and biological classifications.