Malate dehydrogenase: Malate dehydrogenase (MDH) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxaloacetate by using NAD+ and vice versa and this is a reversible reaction. Malate dehydrogenase is not to be confused with malic enzyme, both are different enzymes malic enzyme which catalyzes the conversion of malate to pyruvate and producing NADPH. Malate dehydrogenase is also involved in gluconeogenesis, in which the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is based upon pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. The malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane to get the oxaloacetate out …show more content…
The oxidation of these molecules is primarily used to transform the energy contained in these molecules into ATP. ATP os a large source of energy for muscle contractions and can therefore be referred to as "energy currency" of the cells. The fuel molecules is first converted into acetyl-CoA and then can be inserted in the Krebs Cycle. Looking at the path of a nutrient, such as glucose, the oxidation of the molecule takes place in the glycolysis. The product of the glycolysis is pyruvate. In a further reaction, which is catalyzed by the enzyme complex pyruvate dehydrogenase, acetyl-CoA is formed out of pyruvate, which can be introduced into the citric acid cycle or Krebs Cycle. In an eight-step reaction sequence, the acetyl group of acetyl-CoA is oxidized into two molecules of CO2. These reactions are catalyzed by eight different enzymes. Instead of producing high amounts of ATP, eight electrons were removed from the acetyl group and transferred to the co-enzymes NAD+ and FAD, which are reduced to NADH and FADH2. They are therefore called electron carrier co-enzymes and are used to transport electrons from the Krebs cycle to the respiratory chain. Through a series of molecules, the reduced coenzyme NADH and FADH2 are oxidized and the released electrons were used to reduce O2. Finally, the electrons that are released …show more content…
Thus, some of the citric acid cycle are intermediates for other important reactions like the biosynthesis of glucose, fatty acids and amino acids. Due to the many functions of the citric acid cycle is also considered to be the "central hub of metabolism". This is because, as most of the absorbed nutrients, the fuel molecules are oxidized ultimately within the Krebs Cycle and its intermediates are used for various biosynthetic pathways. Figuratively, one can look at the citric acid cycle as a roundabout introduce, in which the nutrients (carbohydrates, fatty acids and amino acids) drive in and drive out again at the different locations for the synthesis of other