Arsenate (HAsO42) is a potent poison to almost all living systems. Among other e

Question

Arsenate (HAsO42) 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-1-arseno-3-phosphate. This product is a highly unstable compound that immediately undergoes nonenzymatic hydrolysis into glycerate-3-phosphate and free arsenate.

Use of arsenate instead of phosphate at step [ Select ] ["Gly-1", "Gly-3", "Gly-6", "Gly-10"] results in spontaneous hydrolysis of the arseno intermediate without conservation of the energy of the bond as ATP. This results in [ Select ] ["two", "three", "four"] molecules [ Select ] ["less", "more"] of ATP per molecule of glucose, so the energy yield under [ Select ] ["aerobic", "anaerobic"] conditions is [ Select ] ["negative", "zero", "positive"] , and the arsenate is therefore fatal.

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Use of arsenate instead of phosphate at step Gly-6 results in spontaneous hydrolysis of the arseno intermediate without conservation of the energy of the bond as ATP. This results in two molecules less of ATP per molecule of glucose, so the energy yield under anaerobic conditions is zero, and the arsenate is therefore fatal.

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