chapter 3

  • Chemoorganotrophs: Obtain energy and reducing power from organic compounds.

  • Chemolithotrophs: Obtain energy and reducing power from inorganic compounds.

  • Heterotrophs: Obtain carbon from organic sources.

  • Autotrophs (Primary Producers): Obtain carbon from carbon dioxide (CO2).

  • Chemoorganotrophs: Organisms that obtain energy and reducing power from organic compounds, such as sugars and fats. Key examples include many bacteria and fungi that decompose organic matter. They play essential roles in nutrient cycling in ecosystems.

  • Chemolithotrophs: These organisms derive energy from inorganic sources, such as hydrogen sulfide or ammonia. They are crucial in environments where organic material is scarce, like deep-sea vents.

  • Heterotrophs: Heterotrophs cannot make their own food and rely on organic materials for carbon. They can be classified into various groups, such as animals, fungi, and some bacteria.

•Autotrophs: Often referred to as primary producers, autotrophs synthesize their own food using carbon dioxide (CO2). They are vital in food chains as they convert solar energy into chemical energy through photosynthesis or through chemosynthesis in some bacteria.

Page 3: Oxidation-Reduction Reaction Example

  • Reactants:

    • Glucose (C6H12O6) + 6 O2

  • Products:

    • 6 CO2 + 6 H2O

  • Reactions:

    • Glucose is oxidized to CO2.

    • Oxygen is reduced to water (H2O).

    • Reactants: C6H12O6 + 6 O2

    • Products: 6 CO2 + 6 H2O

    • Oxidation: In this reaction, glucose is oxidized to carbon dioxide (CO2), meaning it loses electrons. This process releases energy that cells can use.

    Reduction: Oxygen (O2) is reduced to water (H2O), meaning it gains electrons. This reduction is crucial in the process of cellular respiration, allowing for energy production.

Page 4: Glycolysis (Embden-Meyerhof-Parnas Pathway)

Stages of Glycolysis

  • Stage I:

    • Conversion of glucose into intermediates using ATP.

    • Key enzymes include hexokinase, phosphofructokinase.

  • Stage II:

    • Conversion of intermediates into pyruvate.

    • Production of 2 ATP and 2 NADH.

Intermediates and Enzymes

  • Intermediates include:

    • Glyceraldehyde-3-P, 1,3-Bisphosphoglycerate, Phosphoenolpyruvate.

  • Enzymes: Include Glyceraldehyde-3-P dehydrogenase, Pyruvate kinase.

Page 5: Enzyme Catalysis and Activation Energy

  • Enzymes: Catalysts that lower activation energy to increase the rate of reactions.

    • Typically consist of proteins (some RNA functions as enzymes).

    • Highly specific in their action due to unique structural configurations.

    • Enzymes: Enzymes function as catalysts that lower the activation energy needed for reactions to proceed. Enzyme specificity allows for precise control over metabolic pathways, reducing the chances of unwanted side reactions.

Page 7: The Citric Acid Cycle (CAC)

  • Initiation: Begins with acetyl-CoA condensing with oxaloacetate to form citrate.

  • Reactions: Through various transformations, citrate undergoes multiple oxidations leading back to oxaloacetate.

  • Main Enzymes: Citrate synthase, Isocitrate dehydrogenase, Succinate dehydrogenase.

  • Outcome: Produces NADH, FADH2, CO2, and ATP (or GTP).

Page 8: Generation of Proton Motive Force

  • Electron Transport Chain (ETC): Occurs in the plasma membrane (prokaryotes) or mitochondrial inner membrane (eukaryotes).

Page 9: ATP Synthase Functionality

  • Reversible ATP Synthase: Responsible for ATP production during oxidative phosphorylation (OP) derived from the ETC.

  • ATP Production Mechanism: This mechanism illustrates how ATP synthase harnesses the proton motive force generated by the ETC to synthesize ATP via oxidative phosphorylation, highlighting the coupling of electron transport and ATP synthesis.

Page 10: Metabolic Diversity and Oxygen Relation

  • Relationship: The diversity in metabolic types relates directly to the availability of oxygen in the environment.

  • Chemoorganotrophs: bacteria and fungi

  • Chemolithotrophs: hydrogen sulfide or ammonia

  • Heterotrophs: animals and fungi

  • Autotrophs: plants (photoautotrophs) and some bacteria, chemosynthesis (chemoautrotrophs)

Page 11: Electron Transport Chain Complexes

  • Energy Flow: Electrons are transferred through multiple complexes, facilitating proton transport across the membrane.

  • Outcome: Helps create the conditions for ATP synthesis.

Page 12: Principles of Fermentation

  • Fermentation Process: Involves substrate-level phosphorylation (Pi directly transferred from substrate to ADP = ATP without ETC or O2) and redox balance through the conversion of pyruvate.

    • occurs in absence of oxygen (anaerobic)

  • Products: Useful fermentation processes include the production of ethanol, CO2, yogurt, cheese, etc.

Page 13: Comparison of Respiration Processes

  • Aerobic Respiration:

    • Complete oxidation of organics, oxygen present.

    • ATP produced via substrate-level phosphorylation (SLP) and oxidative phosphorylation (OP).

    • High ATP yield.

  • Anaerobic Respiration:

    • External electron acceptors are used, no O2 required.

    • Medium ATP yield.

  • Fermentation:

    • Internal electron acceptors used, no O2 required.

    • Low ATP yield.

Page 14: Energetics in Fermentation and Aerobic Respiration

  • Lactic Acid fermentation: Glucose + 2 ADP + 2 Pi → 2 Lactate + 2 ATP

  • Aerobic Respiration: Glucose + 6 O2 + 38 ADP + 38 Pi → 6 CO2 + 6H2O + 38 ATP

Page 15: Discussion on ATP Yield from Glucose

  • Maximal ATP Yield: 38 ATP potentially from one glucose molecule.

  • Actual Yield: Often lower due to:

    • Microbial adaptation to low oxygen or anaerobic conditions.

    • Use of less efficient ATP pathways to produce energy quickly.

    • High acidity stress from excess ATP production.