Cellular Respiration Study Notes

Cellular Respiration

Aerobic Cellular Respiration

  • Definition: A biochemical process where cells utilize oxygen to convert glucose into energy.
  • Characteristics:
    • Identified as an endergonic process, meaning it consumes energy.
    • Energy source for this process is derived from glucose.

Overall Equation of Aerobic Cellular Respiration

  • Chemical Equation:
    C6H{12}O6 + 6O2
    ightarrow 6CO2 + 6H2O
  • Reactants:
    • Glucose: Oxidized during respiration
    • Oxygen: Reduced to form water
  • Products:
    • Carbon Dioxide (CO2)
    • Water (H2O)

Carrier Molecule of Electrons

  • The molecule responsible for carrying electrons between reactants is NAD+, which serves as the main electron carrier.
  • FAD is another carrier used in the process.

Structure of Mitochondrion

  • Components:
    • Matrix: Innermost compartment of the mitochondrion
    • Intermembrane Space: Area between the inner and outer membranes
    • Two Membranes:
    • Inner membrane
    • Outer membrane
  • Function: Mitochondria are crucial for aerobic cellular respiration reactions.
Four Stages of Aerobic Cellular Respiration

  1. Glycolysis

    • Location: Cytoplasm
    • ATP Production: Major ATP producing phase (Net gain of 2 ATP)

  2. Pyruvate Processing

    • Location: Mitochondrial matrix

  3. Citric Acid Cycle (Krebs Cycle)

    • Location: Mitochondrial matrix
    • Significance: Considered a major oxidation step
    • ATP Production: A small amount of ATP is produced here (1 per Acetyl-CoA)

  4. Oxidative Phosphorylation

    • Location: Inner mitochondrial membrane
    • ATP Production: Produces approximately 26-28 ATP from the electrons transported through the electron transport chain (ETC).

Glycolysis Overview

  • Process Overview:
    • Occurs in the cytoplasm
    • Starting Material: Glucose
    • Products:
    • 2 Pyruvate molecules
    • ATP: 2 ATP invested; 4 ATP produced, yielding a net gain of 2 ATP.
    • High Energy Electrons are harvested, converting NAD+ to NADH.

Pyruvate Processing

  • Description:
    • Pyruvate enters the mitochondria and is processed in the mitochondrial matrix.
    • Reaction: Pyruvate is catabolized to form Acetyl-CoA, producing one molecule of CO2 as a low-energy by-product.
    • Coenzyme: Acetyl-CoA formation involves attachment of coenzyme A.
    • Yields: 2 Acetyl-CoA per glucose, NAD+ is reduced to NADH.

Citric Acid Cycle

  • Overview:
    • Occurs within the mitochondrial matrix.
    • Reactants: Acetyl-CoA
    • Products:
    • NADH
    • FADH2
    • ATP, and release of CO2.
    • Major oxidation step as it harvests high energy electrons and results in a small ATP yield.

Oxidative Phosphorylation

  • Driving Force:
    • The energy from high-energy electrons (NADH and FADH2) is used to drive ATP synthesis via ATP synthase.
    • The protons (H+) create a gradient, facilitating the production of ATP.
    • End Result: Oxygen acts as the final electron acceptor, forming H2O.

Fate of Carbon and Oxygen

  • Glucose: The carbon in glucose is converted to CO2 through metabolic processes.
  • O2: Utilized to form water (H2O) during oxidative phosphorylation.

Fermentation

  • Anaerobic Process: Occurs when oxygen is scarce (e.g., in active animal muscle cells).
  • Importance of NAD+ Regeneration: Essential for glycolysis to continue under anaerobic conditions, as NAD+ is required for the conversion of G3P to pyruvate.
  • By-products:
    • In animal cells: Lactic acid
    • In yeast: Ethanol and CO2.
  • Comparison of ATP Yield: There is a higher ATP yield in the presence of oxygen compared to anaerobic conditions, emphasizing the efficiency of aerobic respiration.

Summary

  • Cellular respiration is a complex, multi-step process critical for energy production in cells. It involves multiple stages, starting with glycolysis, followed by pyruvate processing, the citric acid cycle, and ending with oxidative phosphorylation, with significant implications for understanding both metabolic processes and bioenergetics.