In glycolysis, the net gain of ATP per molecule of glucose is typically 2 ATP. However, when we consider other monosaccharides like fructose, mannose, and galactose, the process varies slightly due to the different pathways these sugars take to enter glycolysis.
Fructose: When fructose is metabolized, it is converted into dihydroxyacetone phosphate (DHAP) and glyceraldehyde. Because it bypasses the initial ATP investment phase of glycolysis, the net gain of ATP is 2 ATP, similar to glucose.
Mannose: Mannose is converted into fructose-6-phosphate, which then enters glycolysis. The net gain of ATP from mannose is also 2 ATP, as it follows the same steps as glucose after conversion.
Galactose: Galactose is converted into glucose-6-phosphate before entering glycolysis. Therefore, just like glucose, the metabolism of galactose yields a net gain of 2 ATP in glycolysis.
In summary, the net gain of ATP from glycolysis for fructose, mannose, and galactose is also 2 ATP per monosaccharide, similar to that of glucose.