4.2 Glycolysis - Concepts of Biology

Learning Objectives

• Understand how ATP is used as an energy source by cells.
• Describe the results of glucose breakdown via glycolysis.

ATP: The Energy Currency of the Cell

• ATP (Adenosine Triphosphate): The main energy carrier in cells.
  • Composed of adenine, ribose, and three phosphate groups.
  • Functions like a rechargeable battery for cellular processes.
• ATP Structure:
  • AMP (Adenosine Monophosphate): Adenine + ribose + one phosphate.
  • ADP (Adenosine Diphosphate): AMP + one additional phosphate.
  • ATP: ADP + one more phosphate.
  • High-energy bonds between phosphate groups.
• Energy Release:
  • Breaking ATP into ADP + Pi releases energy.
  • Energy is used for cellular work (e.g., muscle contraction).

Glycolysis: The Initial Step in Glucose Metabolism

• Definition: The first step in breaking down glucose to extract energy.
• Location: Occurs in the cytoplasm of cells.
• Process Overview:
  • Begins with one glucose molecule (6-carbon) and ends with two pyruvate molecules (3-carbon each).
  • Consists of two phases:
    1. Energy Investment Phase:
       • Glucose is split into two 3-carbon molecules using energy.
    2. Energy Payoff Phase:
       • Produces ATP and NADH.
• Net Yield: Two ATP molecules per glucose if pyruvate can't be further processed.

Importance of Glycolysis

• Universal Process: Occurs in almost all living organisms.
• Example: Red blood cells rely solely on glycolysis for ATP.

Conclusion

• Glycolysis is a crucial biological process that enables cells to extract energy from glucose efficiently.
• ATP plays a fundamental role in energy transfer and utilization within cells.

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Reference: Access for free at OpenStax Glycolysis