What are the pathways of glucose?

The breakdown of glucose can be shown by following diagram:

In all organisms, a molecule of glucose (6 carbon molecule) is first converted into 2 molecules of pyruvate (3 carbon molecule) in cytoplasm and is termed GLYCOLYSIS.
Further breakdown of pyruvate can take any of three pathways:
In Yeast: In yeast, breakdown of pyruvate take place in absence of oxygen. Due to this, it is called anaerobic respiration. Pyruvate is broken down into ethanol and carbon dioxide and energy. This process is also named fermentation process.
In muscle cells: During strenuous physical activity, the energy demand from muscle cells suddenly increases. This is compensated by anaerobic respiration in muscle cells. In such a situation, pyruvate is broken down into lactic acid and energy.
In mitochondria: In this case, breakdown of pyruvate takes place in presence of oxygen. Due to this, it is called aerobic respiration. Pyruvate is broken down into carbon dioxide and water and energy. Aerobic respiration occurs in most of the living beings, producing, more ATP as compared to other process of anaerobic respiration.