Explain how in glycolysis the splitting of one glucose molecule results in 4 ATP but there is only a net gain of 2 ATP.

During glycolisys in cytoplasm, first step involves adding two phosphates to glucose molecule. This step requires the use of two ATP molecules. The next step is splitting 6 carbons glucose into two 3 carbons pyruvates. This step produces 4 ATPs and 2 NADHs. However, since we used up two ATPs during the initial phosphorylation, the net gain is only 2 ATPs