Biochemistry

Amino Acid Biosynthesis Glutamate and Aspartate Glutamate and aspartate are synthesized from their widely distributed a-keto acid precursors by simple 1-step transamination reactions. The former catalyzed by glutamate dehydrogenase and the latter by aspartate aminotransferase, AST. Aspartate is also derived from asparagine through the action of asparaginase. The importance of glutamate as a common intracellular amino donor for transamination reactions and of a…

The Effects of Enzyme Inhibitors Enzymes can be inhibited competitively, when the substrate and inhibitor compete for binding to the same active site or noncompetitively, when the inhibitor binds somewhere else on the enzyme molecule reducing its efficiency. The distinction can be determined by plotting enzyme activity with and without the inhibitor present. Competitive Inhibition In the presence of a competitive inhibitor, it takes a higher su…

Cori Cycle The Cori Cycle operates during exercise, when aerobic metabolism in muscle cannot keep up with energy needs. For a brief burst of ATP utilization, muscle cells utilize ~P stored as phosphocreatine. For more extended exercise, ATP is mainly provided by Glycolysis. Lactate, produced from pyruvate, passes via the blood to the liver where it is converted to glucose. The glucose may travel back to the muscle to fuel Glycolysis. The Cori Cycle costs…

VITAMIN C: ASCORBIC ACID, ASCORBATE Vitamin C benefits the body by holding cells together through collagen synthesis; collagen is a connective tissue that holds muscles, bones, and other tissues together. Vitamin C also aids in wound healing, bone and tooth formation, strengthening blood vessel walls, improving immune system function, increasing absorption and utilization of iron, and acting as an antioxidant. RDA The Recommended Dietary Allowance (RDA) for V…

Acyl-CoA Synthases (Thiokinases), associated with endoplasmic reticulum membranes and the outer mitochondrial membrane, catalyze activation of long chain fatty acids, esterifying them to coenzyme A, as shown at right. This process is ATP-dependent, and occurs in 2 steps. There are different Acyl-CoA Synthases for fatty acids of different chain lengths.  Exergonic hydrolysis of PPi (P~P), catalyzed by Pyrophosphatase, makes the coupled reaction spontaneous. O…