Oxidative Phosphorylation Notes

Oxidative Phosphorylation

Introduction

• Oxidative phosphorylation is the final stage of cellular respiration.
• It follows glycolysis and the Krebs cycle.
• This stage uses hydrogens harvested in previous stages to produce ATP molecules.

Overview of Cellular Respiration

• Glycolysis:
  • First step in cellular respiration.
  • Occurs in the cytosol.
  • Purpose: To access hydrogens from glucose molecules.
• Krebs Cycle:
  • Second step in cellular respiration.
  • Occurs inside the mitochondrial matrix.
  • Purpose: To harvest hydrogens, which are the main energy carriers.
• Oxidative Phosphorylation:
  • Final stage where ATP is produced.
  • Uses hydrogens to add phosphorus and create ATP molecules.

Location of Oxidative Phosphorylation

• Glycolysis takes place in the cytosol.
• The Krebs cycle takes place inside the matrix of the mitochondria.
• Oxidative phosphorylation takes place on the inner membrane of the mitochondria.
• Mitochondria structure includes:
  • Outer membrane.
  • Inner membrane: The location of the process.

Components of the Inner Membrane

• Phospholipid Layer:
  • Composed of yellow ball-like structures.
• Cytochromes:
  • Large protein channels embedded in the phospholipid layer.
  • Assist in ATP production by passing along hydrogen electrons.
  • The hydrogen jumps from one cytochrome to the next.

ATP Synthesis

• Hydrogen moves through the cytochrome.
• This movement allows ADP to fuse with a phosphate, creating ATP and water.

Step-by-Step Explanation of Oxidative Phosphorylation

• The explanation uses a schematic drawing, not a physical model.
• A flight of stairs represents the inner membrane of the mitochondria.
• Each step represents a drop in the energy level of the hydrogen.

Process Initiation

• NADH:
  • Hydrogen carrier from the Krebs cycle.
  • Delivers hydrogen to start the ATP production process.
  • After delivering the hydrogen, NADH returns to the Krebs cycle to collect more hydrogen.

Energy Transfer

• The hydrogen atom (electron) goes through a process of giving off its energy.
• Each step down the staircase represents the hydrogen's energy level decreasing.
• ADP and Phosphate:
  • Required to form ATP.
  • ADP and phosphate swoop past the hydrogen.
  • The hydrogen provides the necessary energy for the phosphate to join ADP, creating ATP.
  • As ATP is formed, the hydrogen lowers its energy level and moves down a step.

Final Hydrogen Acceptor

• After multiple steps of ATP production, the hydrogen molecule has a low energy level.
• Oxygen:
  • The final acceptor of the hydrogen molecule.
  • Combines with hydrogen to produce water ($H_2O$).
  • Water is a byproduct and is exhaled as water vapor, along with carbon dioxide ($CO_2$).

ATP Production and Usage

• Many ATP molecules are produced from the process.
• ATP provides energy for:
  • Growth.
  • Movement.
  • Other life processes.
• Approximately 32 ATP molecules are produced throughout the entire cellular respiration cycle.

Terminology Recap

• Cristae:
  • Folds inside the mitochondria.
  • Form the inner membrane.
  • Location of oxidative phosphorylation.
• Cytochromes:
  • Proteins embedded in the inner membrane.
  • Assist in the production of ATP.
• Energy Carriers:
  • ATP: The primary energy carrier.
  • NADH: Carries hydrogen atoms.
• Phosphorylation:
  • The process of adding a phosphate group to ADP to form ATP. (ADP + P_i "/></ ATP)