Question

Addition of Phosphate groups to molecules usually requires ATP as source of energy but in glycolysis a phosphate group is added to Glyceraldehyde-3-P without a ATP molecule. How?

Answer 1

Glyceraldehyde-3-P (GAP)  is also known as  triose phosphate. ATP molecule is not required when adding a phosphate group to Glyceraldehyde-3-P since the triosephosphate isomerase enzyme rapidly transforms the molecules so that they can be used in the next step of glycolysis.