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 essentially is the reverse of the photosynthesis. It is a series of metabolic processes in which an organism is capable of converting the chemical energy into a more usable form of energy that can sustain the growth of the organism. This form of energy is the ATP or adenosine triphosphate.