The first step of the process of nutrition involves the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule. This three-carbon molecule is called pyruvate. Pyruvate is important in cellular respiration, the process by which cells obtain energy from glucose. During this process, glucose is broken down in the cytoplasm of cells through a series of chemical reactions. Pyruvate is then further processed in the mitochondria to produce ATP, the main energy source for cells. It is important to note that options 2, 3, and 4 (propanol, propane, and methanol, respectively) are incorrect and not involved in the initial breakdown of glucose in the process of nutrition.