"There's a big difference in the chemicals formed in an interstellar hydrogen cloud and the chemicals required for the Krebbs Cycle"
We also now know of life forms that do not use the krebs cycle as their basis of energy intake. Chemosynthesis has been found in animals near hydrothermal vents which use sulfur as their primary energy source.
And you'll find the organic molecules they use are just as complicated, involved, and delicate as those in the Krebs Cycle, so the initial point still stands.