Hemoproteins in cell metabolism

The alliance between heme and a protein, to make a hemoprotein, completely alters the chemistry of the heme. If we are to appreciate how, then 

Two distinct peripheral processes can be identified, once again mirroring the outer and inner sphere mechanisms just mentioned. The first involves simple orbited overlap between the reactant s rr-system and that of the porphyrin near the mrao-position. No o-bonds are formed or broken, only electron transfer (i.e. an outer sphere process) takes place, and as such is likely to be reversible. The second process involves transfer of an atom along with an electron (i.e. an inner sphere process). The species can be hydrogen or a free radical. Transfer is likely to be irreversible and involves formation and breaking of a-bonds at the meso-position. Both of these peripheral processes require the metal to be in conjugation with the porphyrin TT-system for oxidation of the metal to take place. This happens 

The cytochromes are probably the most important class of electron-transfer proteins. They are involved in photosynthesis, embedded in the thylakoid membranes of chloroplasts. They are also involved in the opposite process of cellular respiration in plants and animals, which occurs in the membranes of mitochondria.  

It can easily be overlooked just how important ATP s3mthesis is, for it is the hydrolysis of ATP back to ADP that generates the energy we need to live. For example, an adult male in a sedentary occupation bums about 3000 kcal of energy per day. This requires the daily hydrolysis of about 200 kg of ATP, which presents a problem as the body only has, on average, 50 g of the stuff So ATP has to be hydrolysed down to ADP and resynthesised back to ATP many thousands of times in the course of the day. Cytochrome c is just one of the links in the chain of electron carrier proteins that ultimately produce ATP. 

The site of this electron-transporting chain, and the enzymes that produce ATP, are cristae within the cell s mini-power station, the mitochondrion. Each mitochondrion consists of a space, the matrix, which contains 

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