Role in Cellular Respiration

Mitochondria are found in the cell body and all processes of the neuron. They possess a double membrane and their own DNA and they play a role in cellular respiration and energy synthesis. Mitochondria contain enzymes essential for energy production in the form of adenosine triphosphate (ATP). 

Vitamin E in an antioxidant that acts as a scavenger for molecular oxygen and free radicals. It also has a role in cellular respiration. 

Its previous discovery in yeast, as well as its presence in heart muscle extracts, emphasized the metaboUc significance of nicotinamide. The emergence of nicotinic acid or nicotinamide as a nutritional essential came from the demonstration by Elvehjem et al. that black tongue in dogs could be cured and prevented by its addition to the deficient diet. Simultaneously, FoutS et alJ, Smith et al. and Spies et al. reported the successful treatment of pellagra in human subjects. Its universal occurrence in living tissue and its fundamental role in cellular respiration are now well estabhshedi . 

Phenols undergo oxidation to quinones. Quinones are biologically important because their redox properties play a significant role in cellular respiration. 

The ready reversibility of this reaction is essential to the role that qumones play in cellular respiration the process by which an organism uses molecular oxygen to convert Its food to carbon dioxide water and energy Electrons are not transferred directly from the substrate molecule to oxygen but instead are transferred by way of an electron trans port chain involving a succession of oxidation-reduction reactions A key component of this electron transport chain is the substance known as ubiquinone or coenzyme Q... 

The essentiality of copper arises from its specific incorporation into a large number of enzymatic and structural proteins. The role of copper in oxidation-reduction enzyme activities is the consequence of its ability to function as an electron transfer intermediate. Thus, copper is present in enzymes involved in cellular respiration, free radical defense, neurotransmitter function, connective tissue biosynthesis, and cellular iron metabolism. 

Because of the role of mitochondria in cellular respiration and energy production, efforts to elucidate the mechanism of thyroid hormone action in metabolism and calorigenesis have focused on mitochondrial studies. Thyroid hormones in vitro are known to uncouple oxidative phosphorylation in isolated mitochondria, but these effects occur at unphysiological doses of T4. In physiological concentrations, T4 increases adenosine triphosphate (ATP) formation and the number and inner membrane surface area of mitochondria (21), but T4 does not reduce the efficiency of oxidative phosphorylation. Furthermore, 2,4-dinitrophenol, a classic uncoupler of oxidative phosphorylation, can neither relieve hypothyroidism nor duplicate other physiological effects of thyroid hormones. 

It has been shown that these organelles contain peroxidase, catalase, uricase, and a number of other oxidases, such as D amino oxidase, L-hydroxy acid oxidase, and even isocitrate dehydrogenase [264]. Because of their content in peroxidase, microbodies have been renamed peroxisomes. Nothing is known of their role in cellular physiology. Usually on the basis of circumstantial evidence they have been suspected to play a role in purine (because of the presence of xanthine oxidase and allantoinase in the kidney and liver of chicken microbodies), cholesterol, lipid, and steroid metabolisms, gluconeogenesis, photosynthesis, and respiration. 

Quinones are widespread in natnre (Thomson, 1971) and have a variety of functions in the life cycles of most kinds of living organisms. These diketones are fonnd in higher plants, fungi, bacteria, and throughout the animal kingdom, and they play a central role in many biosynthetic processes that involve electron transport, such as cellular respiration (nbiqninone) and photosynthesis (plastoqninone). Vitamin K is an important factor in blood... 

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