Question

Which of the following is correct? Which of the following is correct? Most of the ATP are produced by substrate-level phosphorylation. Glycolysis relies on substrate-level oxidation for the four ATP produced in this pathway. Each FADH2 yields about 1.5 ATP via oxidative phosphorylation. Most ATP from cellular respiration are produced directly in the citric acid (Krebs) cycle.

Answer 1

Answer:

Each FADH2 yields about 1.5 ATP via oxidative phosphorylation.

Explanation:

Most of the ATP molecules are produced by oxidative phosphorylation, not by substrate-level phosphorylation. During glycolysis, 2 ATP molecules per glucose are produced by substrate-level phosphorylation. Similarly, Kreb's cycle also yields 2 ATP per glucose by substrate-level phosphorylation.

For each pair of electrons transferred to O2 from FADH2 via electron transport chain, 4 and 2 protons are pumped from matrix towards the intermembrane space by complex III and complex IV respectively. It generates the proton concentration gradient required to drive the synthesis of 1.5 ATP molecules. Since oxidation of FADH2 is coupled to the phosphorylation of ADP to form ATP, the process is called oxidative phosphorylation.