And because delta G is proportional to things like the ATP-ADP ratio, you can imagine if this ratio gets too high, some of the steps might no longer be favorable to occur. Those are two examples where we could directly couple the oxidation of carbon to a phosphorylation event that ultimately allowed us to favorably produce ATP to maintain an ATP/ADP ratio that's high and is present in cells. One highly conserved region in the protein kinase core is the glycine-rich loop (or G-loop), a highly flexible loop that is characterized by a consensus GxGxxG sequence. The G-loop points toward the catalytic cleft and functions to bind and position ATP for phosphotransfer. Like mentioned previously, the electron transport chain allows the standard free energy to be released in smaller, more appropriate quantities - this, when coupled with ATP synthesis, results in a process called oxidative phosphorylation. This type of phosphorylation involves the direct synthesis of ATP from ADP and a reactive intermediate, typically a high energy phosphate-containing molecule. Substrate level phosphorylation is a relatively minor contributor to the total synthesis of triphosphates by cells. The cellular environment also contributes to differences in the Δ G value since ATP hydrolysis is dependent not only on the studied cell, but also on the surrounding tissue and even the compartment within the cell. Write coupled reaction schemes showing how ATP hydrolysis drives thermodynamically unfavorable reactions such as glucose phosphorylation or peptide bond formation, applying Hess's Law to calculate net ΔG°. In turn, the term Delta G (ox,ap) results from the proton motive force and the generation of ATP in the matrix space including the ATP-ADP exchange, whereas the phosphorylation state of the CHEP-sytem is described by Delta G (ATP,cyt). Although most often discussed in terms of the consumption of ATP (GTP and others), phosphorylation must also be involved in the production of these energy-rich species. Explain how hexokinase uses an induced-fit conformational change to exclude water from the active site, thereby preventing ATP hydrolysis and ensuring phosphoryl transfer to glucose.