Fate of Pyruvic Acid: The breakdown of pyruvic acid takes place in mitochondria and the molecules formed depend on the type of respiration in a particular organism. Respiration is of two types, viz. aerobic respiration and anaerobic respiration.Anaerobic Respiration: This type of respiration happens in the presence of oxygen. Pyruvic acid is converted into carbon dioxide. Energy is released and water molecule is also formed at the end of this process.Aerobic Respiration: This type of respiration happens in the absence of oxygen. Pyruvic acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed in case of anaerobic respiration in microbes; like yeast or bacteria. Lactic acid is formed in some microbes as well as in the muscle cells.

The process of breakdown of glucose molecules involves two major stages - glycolysis (anaerobic respiration) and aerobic respiration ( Kreb's cycle and ETS Pathway). Cellular respiration begins at this stage in the cytoplasm of the cells, and yields 2 carbon-based molecules called pyruvate, and 2 molecules of ATP

Three Pathways of Breakdown in Living Organisms



1. Glycolysis
- Glycolysis is the first step in the breakdown of glucose in living organisms.
- It takes place in the cytoplasm of cells and does not require oxygen.
- During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate.
- This process generates a small amount of ATP, the energy currency of the cell.
- Glycolysis is an essential pathway for energy production, especially in anaerobic conditions.



2. Citric Acid Cycle (Krebs Cycle)
- The citric acid cycle is a series of chemical reactions that occur in the mitochondria of eukaryotic cells.
- It involves the oxidation of acetyl-CoA, a molecule derived from pyruvate, to produce ATP, NADH, and FADH2.
- The citric acid cycle is a central pathway in cellular respiration, which generates the majority of ATP in aerobic organisms.
- It also plays a crucial role in the metabolism of carbohydrates, fats, and proteins.



3. Electron Transport Chain
- The electron transport chain is the final stage of cellular respiration, taking place in the inner mitochondrial membrane.
- It involves the transfer of electrons from NADH and FADH2 to oxygen, producing a large amount of ATP through oxidative phosphorylation.
- This process creates a proton gradient across the membrane, driving ATP synthesis by ATP synthase.
- The electron transport chain is an efficient way to produce energy in aerobic organisms and is essential for their survival.