Why do scientists think that glycolysis evolved before the other stages of cellular respiration?
A Because glycolysis is only seen in prokaryotes
B Because it generates ATP
C Because it does not require oxygen
D Because it requires oxygen
C Because it does not require oxygen
Glycolysis is the metabolic pathway that converts glucose into pyruvate, releasing energy in the form of ATP. One of the reasons scientists believe that glycolysis evolved before the other stages of cellular respiration is because it does not require oxygen to proceed. This indicates that it can occur under anaerobic conditions, which would have been common on early Earth before the atmosphere had significant amounts of oxygen.
Option A is incorrect because glycolysis is not only seen in prokaryotes; it is a universal pathway found in nearly all organisms, including both prokaryotes and eukaryotes.
Option B is incorrect because although glycolysis generates ATP, this attribute alone does not provide evidence for its evolutionary primacy. Other stages of cellular respiration, such as the citric acid cycle and oxidative phosphorylation, also generate ATP but are more evolutionarily advanced processes and require oxygen.
Option D is incorrect because glycolysis does not require oxygen. This enables organisms to produce ATP under anaerobic conditions, which would have been advantageous in the oxygen-poor environment of the early Earth.