Final answer:
A total of 4 ATP molecules are produced via substrate level phosphorylation by the end of the Kreb's cycle for each glucose molecule, which includes 2 ATP from glycolysis and 2 from the Kreb's cycle.
Step-by-step explanation:
By the end of the Kreb's cycle, 1 molecule of glucose produces a total of 4 ATP via substrate level phosphorylation. This includes 2 ATP from glycolysis and 2 ATP (or GTP in some organisms) from the Kreb's cycle itself, since for each glucose molecule, two turns of the cycle are necessary, creating one ATP (or GTP) each turn.
In addition to ATP from substrate level phosphorylation, electron transport contributes to ATP production. The NADH and FADH₂ produced in glycolysis, the transition reaction, and the Kreb's cycle are used in oxidative phosphorylation to produce additional ATP. However, these are not counted in the total from substrate level phosphorylation.