Which molecule must bind to a magnesium cation to be active in cells?

Which molecule must bind to a magnesium cation to be active in cells?

• A. Nicotinamide adenine dinucleotide
• B. Adenosine triphosphate
• C. Glucose
• D. Guanosine triphosphate

Answer: (B)

Magnesium stabilizes the negative charges on the triphosphate tail of nucleotides, which is essential for phosphate transfer in cells. In most phosphorylation reactions, ATP must be in its magnesium-bound form to act effectively as the donor of the gamma phosphate. The Mg2+ ion coordinates with the phosphate oxygens, reducing electrostatic repulsion, helping the enzyme bind ATP properly, and making the γ-phosphate more available for transfer to the substrate. Without Mg2+, ATP is far less efficient as a phosphate donor, and many kinases cannot catalyze the reaction efficiently. NAD+ is a redox coenzyme and doesn’t rely on Mg2+ in the same universal way for its activity. Glucose doesn’t require binding to Mg2+ to be active, and while some GTP-dependent processes also involve Mg2+ binding, ATP’s role as the primary phosphate donor across many cellular reactions makes Mg2+-ATP the most broadly required form.

Magnesium stabilizes the negative charges on the triphosphate tail of nucleotides, which is essential for phosphate transfer in cells. In most phosphorylation reactions, ATP must be in its magnesium-bound form to act effectively as the donor of the gamma phosphate. The Mg2+ ion coordinates with the phosphate oxygens, reducing electrostatic repulsion, helping the enzyme bind ATP properly, and making the γ-phosphate more available for transfer to the substrate. Without Mg2+, ATP is far less efficient as a phosphate donor, and many kinases cannot catalyze the reaction efficiently.

NAD+ is a redox coenzyme and doesn’t rely on Mg2+ in the same universal way for its activity. Glucose doesn’t require binding to Mg2+ to be active, and while some GTP-dependent processes also involve Mg2+ binding, ATP’s role as the primary phosphate donor across many cellular reactions makes Mg2+-ATP the most broadly required form.