Published on November 7, 2010
Krebs Cycle : Krebs Cycle The Reader’s Digest Abridged Version. Things to Know About the Krebs Cycle : Things to Know About the Krebs Cycle It is an aerobic process. Oxygen is required. The Krebs Cycle occurs in Mitochondria of the cell (known as the cellular power plant). Each Glucose molecule nets 2 pyruvic acids. The Krebs Cycle breaksdown 1 pyruvic acid at a time. It begins and ends with Oxaloacetic Acid – a 4 carbon molecule. It is an 8 step cycle that begins when the Acetyl CoA that is a product of Glycolysis is ‘picked up’ by Oxalacetic Acid. Lipids, Proteins and Carbohydrates can all be metabolized in the Krebs Cycle. More ‘Good to Knows’ for the Krebs Cycle : More ‘Good to Knows’ for the Krebs Cycle Oxidation is changing the way molecules share electrons. NAD+ is a co-enzyme (a helper) whose role is to transport electrons. NAD+ is an oxidizing agent. When NAD+ picks up electrons for transport, it becomes NADH. NADH is an electron donor. FAD/FADH2 is a non-protein, chemical compound that binds to the Phosphate Group of the ADP molecule. FAD is found in many breakfast cereals as riboflavin. Like NAD+/NADH, it helps rearrange electrons in chemical reactions. FADH2 has significantly higher energy than FAD. Getting Started in the Krebs Cycle : Getting Started in the Krebs Cycle Pyruvic Acid (produced by Glycolysis) releases Carbon Dioxide. This CO2 is eventually released back into the atmosphere by respiratory expiration. NAD+ (co-enzyme whose role is to transport electrons) comes along and picks up some H+ and Acetic Acid is formed. Acetic Acid is bound to Co-enzyme A and Acetyle CoA is formed. Acetyl CoA enters the Krebs Cycle. Acetyl CoA’s role in the Krebs Cycle is to transport Acetic Acid from one enzyme to another. Now we are ready to get started in the Krebs Cycle… The Krebs Cycle : The Krebs Cycle The Krebs Cycle is an eight step cycle that starts when Acetic Acid binds to the helper molecule Acetyl CoA. Each pyruvic acid molecule yields 3 CO2, 1 ATP, and 5 reduced Enzymes. The CO2s are eventually released via respiratory expiration. The NADH and FADH2 molecules are ‘high energy’ electron donors, that will carry their electrons into the Electron Transport Chain. Summary : Summary The Krebs cycle uses the products of Glycolysis to produce 2 ATP molecules for each molecule of Glucose. The NADH and FADH2 that are high energy co-enzymes (helper molecules) are by-products of the Krebs cycle and continue on to fuel the Electron Transport Chain.