Question

Classify each statement as being involved in substrate-level phosphorylation, oxidative phosphorylation, or both. Substrate-level phosphorylation Oxidative phosphorylation Both Answer Bank Bank oxidation-reduction reactions occuring involves electron transport chains relatively large amounts of ATP produced per glucose molecule oxidized relatively small amounts of ATP produced per glucose molecule oxidized occurs in the cytosol occurs in the mitochondria high-energy phosphate groups transferred to ADP

Answer 1

Ans:

Substrate-level phosphorylation	Oxidative phosphorylation	Both
Relatively small amounts of ATP produced per glucose molecule oxidized Occurs in the cytosol	Oxidation-reduction reactions occurring Involves electron transport chains Relatively large amounts of ATP produced per glucose molecule oxidized	High-energy phosphate groups transferred to ADP Occurs in the mitochondria

Explanation:

In substrate-level phosphorylation, the direct tranfer of a phosphate group from a substrate molecule to ADP to produce ATP. This phosphorylation occurs in cytosol during glycolysis process and 4 ATP molecules are produced of which 2 ATP are used in this process. So, net gain of ATP is 4-2 = 2 during substrate-level phosphorylation. Substrate-level phosphorylation also occurs in mitochondria during TCA cycle when succinyl CoA is converted into succinate.

Oxidative phosphorylation is a oxidation-reduction reaction where O2 is reduced to H2O and NADH and succinate are oxidized. This process occurs in inner mitochondrial membrane. ATP synthesis takes place from ADP + Pi through electron transport chain. The large amounts of ATP (24 to 28 molecules ATP) is produced from free energy released from NADH and FADH2.

In both the phosphorylation process, high-energy phosphate groups transferred to ADP to form ATP.