The flow of this element from the thylakoid compartment to the stroma aids in the regulation of the Calvin cycle. A complex of this element and (*) ATP is the substrate for kinase enzymes in glycolysis. Its divalent ion aids 
The flow of this element from the thylakoid compartment to the stroma aids in the regulation of the Calvin cycle. A complex of this element and (*) ATP is the substrate for kinase enzymes in glycolysis. Its divalent ion aids in hammerhead ribozyme activity and Vitamin D aids in the absorption of the element along with calcium. Epsom salts are composed of this element's sulfate. For 10 points, name this alkaline earth metal located within the porphyrin ring of chlorophyll.
The flow of this element from the thylakoid compartment to the stroma aids in the regulation of the Calvin cycle.
{magnesium} (or {Mg2+})