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Cellular Respiration Study Sheet

Cellular Respiration Overview

Importance of Cellular Respiration

  • All cells require energy continuously, primarily derived from ATP.

  • The methods of ATP production depend on oxygen availability and biological characteristics of the cell.

  • Examples of oxygen-rich environments include normal human activities, while anaerobic processes are observed in yeast and certain bacteria.

Phases of Cellular Respiration

  1. Glycolysis

    • Occurs in the cytoplasm.

    • Converts glucose into pyruvate, produces 2 ATP and 2 NADH.

  2. Link Reaction

    • Takes place in mitochondria. Converts pyruvate to acetyl-CoA, producing CO2 and NADH.

  3. Krebs Cycle

    • Occurs in mitochondria, processes acetyl-CoA, produces ATP, NADH, FADH2, and CO2.

  4. Oxidative Phosphorylation

    • Occurs in mitochondria, uses NADH and FADH2 to produce large amounts of ATP and water. Requires oxygen as the final electron acceptor.

Chemical Process

  • Overall process:C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy

  • Reactants:

    • Glucose and oxygen.

  • Products:

    • Carbon dioxide, water, and ATP.

ATP Production

  • The primary purpose of cellular respiration is to provide energy (ATP) to cells.

  • Total ATP produced per glucose: approximately 38 ATP (but can vary based on conditions).

High Potential Energy Molecules

  • Other than ATP, NADH and FADH2 are important free energy carriers in cellular respiration.

  • They transport high-energy electrons to the electron transport chain during oxidative phosphorylation.

Electron Transport and Coenzymes

  • NAD+ and FAD are coenzymes that facilitate electron transfer.

  • They become reduced to NADH and FADH2 during glycolysis and Krebs Cycle.

  • Oxygen accepts electrons at the end of the electron transport chain, forming water.

  • Oxidation-Reduction Reactions:

    • Oxidation: loss of electrons (e.g., glucose).

    • Reduction: gain of electrons (e.g., NAD+ to NADH).

Anaerobic Respiration

  • Anaerobic processes do not require oxygen and include fermentation (e.g., lactic acid or alcohol fermentation).

  • Glycolysis produces 2 ATP per glucose, but little efficiency compared to aerobic respiration.

  • The fermentation process regenerates NAD+ for glycolysis to continue under low oxygen conditions.

Summary of Cellular Processes

  • Energy/Adenosine Triphosphate (ATP) is necessary for various cellular activities (e.g., muscle contraction, nerve impulse transmission).

  • Lactic acid buildup during vigorous exercise causes the "burn" felt in muscles due to anaerobic metabolism when oxygen is limited.

Evolutionary Implications

  • Oxygen-dependent organisms gained an evolutionary advantage, leading to diversification of life forms in an oxygen-rich environment.