Cellular Respiration Introduction

Overview

• Cellular respiration is a vital biochemical reaction for deriving energy from glucose.
• It involves glucose and oxygen as inputs and produces carbon dioxide, water, and ATP (energy) as outputs.
• There are three main stages:
  • Glycolysis
  • Krebs Cycle (Citric Acid Cycle)
  • Electron Transport Chain
• Presented by Sal Khan at Khan Academy.

Key Details

• Chemical Reaction:
  • Glucose formula: C6H12O6
  • Reaction: 1 mole of glucose + 6 moles of oxygen → 6 moles of carbon dioxide + 6 moles of water + ATP energy.
• Energy Production:
  • The process primarily produces ATP.
  • Up to 38 ATPs can be produced under ideal conditions, but realistically around 29-30 ATPs.

Stages of Cellular Respiration

1. Glycolysis

• Occurs in the cytoplasm.
• Does not require oxygen (anaerobic).
• Splits glucose (6-carbons) into two 3-carbon pyruvate molecules.
• Net gain of 2 ATP molecules (produces 4 ATPs, uses 2 ATPs).
• Produces NADH used in the Electron Transport Chain.

2. Krebs Cycle (Citric Acid Cycle)

• Takes place in the mitochondria.
• Requires oxygen (aerobic).
• Produces 2 ATPs directly.
• Generates additional NADH and FADH2 for Electron Transport Chain.

3. Electron Transport Chain (ETC)

• Located in the inner mitochondrial membrane.
• Requires oxygen (aerobic).
• Produces the bulk of ATPs (~34 ATPs) via oxidative phosphorylation.

Anaerobic Conditions

• Fermentation:
  • Occurs when oxygen is not available.
  • In humans, results in lactic acid fermentation, causing muscle pain.
  • Other organisms (e.g., yeast) perform alcohol fermentation.

Additional Notes

• NADH and FADH2:
  • Produced during Glycolysis and Krebs Cycle, essential for ETC.
  • NADH contributes to most of the ATP production in ETC.
• Importance of Oxygen:
  • Oxygen is crucial for the Krebs Cycle and ETC.
  • Lack of oxygen leads to reliance on glycolysis and fermentation.

Conclusion

• Cellular respiration is crucial for converting glucose into a usable form of energy (ATP).
• Understanding each stage helps in grasping how energy is efficiently produced in cells.

Next steps include exploring redox reactions and detailed mechanisms of each stage.