Which Energy-Production Reactions Were Likely to Have Been Present in the Earliest

Question

Which energy-production reactions were likely to have been present in the earliest cells?
A) glycolysis, Entner-Doudoroff pathway, and Krebs cycle
B) glycolysis, respiration, and bacteriochlorophyll-based photosynthesis
C) respiration and chlorophyll-based photosynthesis in PSI and PSII
D) oxidation-reduction, light-driven ion pumps, and methanogenesis
E) chemiosmosis, substrate-level phosphorylation, and oxygenic photosynthesis

Accepted Answer

The earliest cells likely used simple energy-production mechanisms such as oxidation-reduction reactions, light-driven ion pumps, and methanogenesis, which do not require complex structures or oxygen.