Krebs Cycle and Electron Transport

Objectives

• Summarize the Krebs Cycle
• Summarize the electron transport chain
• Describe the chemiosmotic gradient
• Explain the synthesis of ATP

Those two pyruvate molecules from glycolysis enter the mitochondrion's matrix for the Krebs cycle.

Before the cycle can start, the pyruvic acid is broken down and combined with coenzyme A (CoA).

This forms...

• Acetyl-CoA
• carbon dioxide
• NADH

Krebs Cycle

Krebs Cycle

• Acetyl-CoA+oxaloacetate -> citric acid
• Several steps produce NADH and CO2
• Final step regenerates oxaloacetate
• Must go through twice per glucose

Products

• 6 carbon dioxide molecules
• 4 ATP (including 2 from glycolysis)
• 10 NADH (including 2 from glycolysis)
• 2 FADH2

High-energy electrons are released from NADH and FADH2, and they more through electron transport chains.

As the high-energy electrons are moved through the transport chains, the energy is used to pump protons from the matrix to the intermembrane space.

Pumping the ions across the inner membrane creates a higher concentration of ions in the intermembrane space.

The resulting chemiosmotic gradient allows the ions to flow back to the matrix through ATP synthase.

After passing through the electron transport chain, electrons combine with oxygen to form water.

Energy Produced

• 34 ATP total