Question 21.6: What product would you obtain from the following reaction? C...
Consider the two reactions shown below. Which one represents oxidative phosphorylation and which one represents substrate-level phosphorylation?
(a) Succinyl-SCoA + P_i + \pmb{GDP} \xrightleftharpoons[]{} Succinate + \pmb{GTP} + CoA
(b) \pmb{ADP } + HOPO_3 ^{2+} \xrightarrow[]{ATP synthase} \pmb{ATP } + H_2O
ANALYSIS Both substrate-level phosphorylation and oxidative phosphorylation involve the transfer of a phosphate group and its energy to another molecule. Both may result in the production of ATP. The key difference is that substratelevel phosphorylation involves the transfer of a phosphate group from one molecule to another, whereas oxidative phosphorlyation adds a phosphate ion directly to ADP with the aid of ATP synthase.
Reaction (a), involving the formation of GTP coupled with the conversion of succinyl-SCoA to succinate, is an example of substrate-level phosphorylation. Reaction (b), involving the direct addition of phosphate to ADP by ATP synthase, is oxidative phosphorylation.