In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

2 molecules of ATP

Explanation:

Glycolysis is the anaerobic process (no oxygen required) used in the breakdown of glucose to extract energy. It occurs in the cytoplasm of both prokaryotic and eukaryotic cells. It is the first step of cellular respiration.

Glycolysis is subdivided into two phases: the first phase uses energy (ATP), while the second phase produces it together with pyruvate and NADH.

Two molecules of ATP are required for the first stage of glycolysis, while 4 ATP molecules and 2 NADH molecules are formed in the second stage.