Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

تمرين 11

Arsenate Poisoning. Arsenate (HAsO 4 2 )is a potent poison to almost all living systems. Among other effects, arsenate is known to uncouple the phosphorylation event from the oxidation of glyceraldehyde-3-phosphate. This uncoupling occurs because the enzyme involved, glyceraldehyde- 3-phosphate dehydrogenase, can utilize arsenate instead of inorganic phosphate, forming glycerate-l-arseno-3-phosphate. This product is a highly unstable compound that immediately undergoes nonenzymatic hydrolysis into glycerate-3-phosphate and free arsenate.
(a)In what sense might arsenate be called an uncoupler of substrate-level phosphorylation
(b)Why is arsenate such a toxic substance for an organism that depends critically on glycolysis to meet its energy needs
(c)Can you think of other reactions that are likely to be uncoupled by arsenate in the same way as the glyceraldehyde-3-phosphate dehydrogenase reaction