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.
Suppose an unicellular organism that has the following characteristics (actually, the same characteristics as #1 above but, here they are again): - it lacks organelles that perform aerobic cellular respiration but, can perform this process. - it cannot photosynthesize nor does it use sunlight for any metabolic process.