The process of dehydration synthesis, a chemical reaction which involves the loss of water from the reactants which join to form a larger molecule, is an example of a metabolic process where water is formed. Dehydration synthesis can join smaller amino acids to form a larger polypeptide molecule, or to join simple glucose molecules to form glycogen(animal starch) within the human body. Both of these processes are two examples where a synthesis reaction involves water being released. In cellular respiration, a process which occurs all the time, the two waste products that form are water and carbon dioxide. Here, the human body is excreting water vapor by the process of exhalation. The production of sweat and urine which are both excretory wastes, involve the loss of water from the body. That is why water must be constantly supplied to the body to replenish that which is lost.