Glycolysis

• Glycolysis is the breakdown of glucose to pyruvate

  Occurs in the cytoplasm of cells

  There are two stages to glycolysis:

  1. Energy Investment Phase

  2. Energy Pay off Phase
• 1. Investment phase

  • ATP is required for the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis.

  • Phosphorylation involves the phosphate from ATP being added to the glucose and intermediates breaking it down to ADP.
• 2. Energy pay off phase.

  • The energy investment leads to the generation of more ATP during the energy pay-off stage and results in a net gain of 2 ATP

  
  

  Dehydrogenase enzymes remove hydrogen ions and electrons from the intermediate substrate and pass them to coenzyme NAD to form NADH
• Citric acid cycle

  • In the citric acid cycle the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.

  • During a series of enzyme-controlled steps, citrate is gradually converted back into oxaloacetate

  • This results in the

  • Generation of ATP,

  • Release of carbon dioxide

  • Formation of NADH as dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH
• Electron transport chain (ATP synthesis)

  • The electron transport chain is a series of carrier proteins attached to the inner mitochondrial membrane.

  • Electrons are passed along the electron transport chain releasing energy.

  • This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane.

  • The flow of these hydrogen ions back through the membrane protein ATP synthase results in the production of ATP.

  • Finally, hydrogen ions and electrons combine with oxygen to form water