Phenylketonuria (PKU) can be defined as a rare metabolic disorder caused by a deficiency in the production of the hepatic (liver) enzyme phenylalanine hydroxylase (PAH). PKU is the most serious form of a class of diseases referred to as hyperphenylalaninemia, all of which involve above normal (elevated) levels of phenylalanine in the blood.
All organisms carry out cellular respiration (except viruses) - it is the basic process which supports life as we know it. Viruses, on the other hand, are not always câ¦onsidered to be living, one of the reasons being that they do NOT carry out cellular respiration.
Cellular respiration is a process wherein cells try to use up and break down various substances and particles from food items and convert them to usable energy. Without this process, the various cells in the body will not have the energy needed to perform their functions. Cells that help muscles contract for example will not be able to perform this important function if they do not undergo cellular respiration.