Glucose is a very widespread molecule, and is essential as energy for nearly all life forms. So, it is difficult to pinpoint one form of it's production. It is not artificially made in a lab, but rather through the natural process of photosynthesis in plants. Glucose is one of two products of photosynthesis in which water and carbon dioxide are taken in by plants in the presence of light to produce the sugar(glucose) and oxygen. The process of photosynthesis occurs in countless plants, which are later ingested by humans. In humans, the glucose is not alone in the food taken in. Many foods contain glucose, such as starches, sweeteners, fruits, pasta, rice, etc... However, they must be processed by the body to extract the energy contained in glucose. As the food travels into the stomach, it is broken down and dissolved by stomach acids into it's basic components, often including glucose. Once the food is broken down, it is absorbed into the lining of the intestines, from which glucose travels to the bloodstream. Glucose is required to reach cells through the bloodstream to maintain health, and is assured by the hormones of insulin and glucagon. Glucose is stored and converted as glycogen in liver and muscle cells, and through the use of the two aforementioned hormones is used for energy when necessary to maintain blood glucose homeostasis. Glucose can also be synthesized by reversing the reaction of the oxidation of glucose from pyruvic acid and acetyl CoA. Therefore, glucose can be made from fats and amino acids by first turning them into these substances.