Citric Acid Cycle and Cellular Respiration

Citric Acid Cycle

• Gluconeogenesis is the process of generating glucose from pyruvate.
• Glycogen synthesis is the process of generating glycogen.
• Citric acid cycle generates 150 kJ/mole of ATP, which can occur in the presence or absence of oxygen.

Preparation Step (Step 0)

• Breaks down a 3-carbon chain, releasing 1 molecule of carbon dioxide, to generate a 2-carbon chain that enters the cycle.
• The 2-carbon chain combines with a 4-carbon chain called oxaloacetate to form citric acid, creating a 6-carbon molecule.

TCA Cycle: 8 Steps + Preparation

• Step 1: Pyruvate is converted to Acetyl-CoA, releasing CO₂ and generating NADH.
• Step 2: Citrate is formed from Acetyl-CoA.
• Step 3: Isocitrate is formed, generating NADH.
• Step 4: α-Ketoglutarate is formed, releasing CO₂ and generating NADH.
• Step 5: GTP is generated through substrate-level phosphorylation, converting GDP + Pi to GTP.
• Step 6: The enzyme oxidoreductase generates more NADH and FADH2.
• Step 7: Involves a redox reaction and a ligase reaction, making or breaking double carbon bonds.
• Step 8: Oxaloacetate is regenerated, completing the cycle.

Key Molecules and Processes

• NADH and FADH2 are generated in the citric acid cycle, which will be used to generate more ATP later.
• Redox reactions, such as oxidative decarboxylation, occur throughout the cycle.
• The citric acid cycle is a critical step in cellular respiration, breaking down carbon chains and generating energy.

Learn about the citric acid cycle, gluconeogenesis, glycogenisis, and cellular respiration processes, including the breakdown of molecules and ATP energy production.