These 10 animal facts will amaze you. The face of farming and agriculture has changed drastically over the past 100 years. At the beginning of the 20th century, over 70% of the population of the United States lived and worked on farms, but by 2008, the figure had dropped to less that 3%.
During this process, glucose from food is broken down into carbon dioxide and water, and energy is released. The process of releasing energy from food is called respiration, or cellular respiration as it is a series of steps that take place within living cells. It is important to not confuse respiration, or oxidizing glucose, with breathing.
Cellular respiration has three main steps: glycolysis, the citric acid cycle, and oxidative phosphorylation, where oxygen is used. Step 1: Glycolysis. Glycolysis is the first step in cellular respiration, and it occurs in the main compartment of the cell: the cytoplasm. Cells let glucose in from the blood--the glucose comes from the food we eat. Next, cells convert glucose through several different compounds to make two ATP molecules and a molecule called pyruvate.