Consider the following questions about glutamate dehydrogenase.(a) The reaction has NH3 as a reactant, instead of NH4+, which is far more abundant at physiological pH. Why is NH3 preferred?(b) Glutamate dehydrogenase has a KM for ammonia (NH3) of ~1 mM.However, at physiological pH, the dominant ionic species is ammoniumion, NH4+ (pKa = 9.2). Calculate the velocity (as a fraction of Vmax) that would be achieved by glutamate dehydrogenase if the total intracellularammonia concentration (NH3 + NH4+) is 100 mM (approximatephysiological concentration). Assume a mitochondrial matrix pH of 8.0.(c) The thermodynamic equilibrium for the reaction greatly favors aketoglutarate reduction; yet in mitochondria the enzyme acts primarily to oxidize glutamate to a-ketoglutarate. Explain.(d) Propose a reasonable mechanism for this reaction.
Electron Transport Chain
The electron transport chain, also known as the electron transport system, is a group of proteins that transfer electrons through a membrane within mitochondria to create a gradient of protons that drives adenosine triphosphate (ATP)synthesis. The cell uses ATP as an energy source for metabolic processes and cellular functions. ETC involves series of reactions that convert redox energy from NADH (nicotinamide adenine dinucleotide (NAD) + hydrogen (H)) and FADH2(flavin adenine dinucleotide (FAD)) oxidation into proton-motive force(PMF), which is then used to synthesize ATP through conformational changes in the ATP synthase complex, a process known as oxidative phosphorylation.
Metabolism
Picture a campfire. It keeps the body warm on a cold night and provides light. To ensure that the fire keeps burning, fuel needs to be added(pieces of wood in this case). When a small piece is added, the fire burns bright for a bit and then dies down unless more wood is added. But, if too many pieces are placed at a time, the fire escalates and burns for a longer time, without actually burning away all the pieces that have been added. Many of them, especially the larger chunks or damp pieces, remain unburnt.
Cellular Respiration
Cellular respiration is the cellular process involved in the generation of adenosine triphosphate (ATP) molecules from the organic nutritional source obtained from the diet. It is a universal process observed in all types of life forms. The glucose (chemical formula C6H12O6) molecules are the preferred raw material for cell respiration as it possesses a simple structure and is highly efficient in nature.
Consider the following questions about glutamate dehydrogenase.
(a) The reaction has NH3 as a reactant, instead of NH4+, which is far more abundant at physiological pH. Why is NH3 preferred?
(b) Glutamate dehydrogenase has a KM for ammonia (NH3) of ~1 mM.
However, at physiological pH, the dominant ionic species is ammonium
ion, NH4+ (pKa = 9.2). Calculate the velocity (as a fraction of Vmax) that would be achieved by glutamate dehydrogenase if the total intracellular
ammonia concentration (NH3 + NH4+) is 100 mM (approximate
physiological concentration). Assume a mitochondrial matrix pH of 8.0.
(c) The
(d) Propose a reasonable mechanism for this reaction.
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