Glycolysis:

Glycolysis Overview

Definition of Glycolysis

• Glycolysis is a metabolic pathway.
• It degrades six-carbon glucose molecules to three-carbon pyruvate molecules.
• It is an anaerobic process (occurs without oxygen).

Learning Objectives

• Understand the conversion of glucose to pyruvate in glycolysis.

Energy Investment Phase (Reactions 1-5)

• Key Points:
  • Requires energy input to add phosphate groups to glucose.
  • Converts glucose to two three-carbon molecules (glyceraldehyde-3-phosphate).

Energy Production Phase (Reactions 6-10)

• Key Points:
  • Energy is generated from the hydrolysis of energy-rich phosphate compounds.
  • Four ATP molecules are produced through substrate-level phosphorylation.

Overall Reaction of Glycolysis

• Key Points:
  • Two ATP are used to add phosphate to glucose and fructose-6-phosphate.
  • Four ATP are produced, resulting in a net gain of 2 ATP and 2 NADH after subtracting the initial ATP used.

Regulation of Glycolysis

• Key Enzymes Involved:
  • Hexokinase (Reaction 1):
  • Inhibited by high levels of glucose-6-phosphate.
  • Prevents the phosphorylation of glucose.
  • Phosphofructokinase (Reaction 3):
  • An allosteric enzyme.
  • Inhibited by high ATP levels.
  • Activated by high ADP and AMP levels.
  • Pyruvate Kinase (Reaction 10):
  • Another allosteric enzyme.
  • Inhibited by high ATP or acetyl CoA levels.

Summary of Glycolysis

• Glycolysis serves as the first step in cellular respiration, providing energy through the breakdown of glucose into pyruvate.
• Key phases include energy investment and energy production, regulated by specific enzymes to balance energy needs of the cell.