Question

Why is MgATP2− , instead of ATP4− , a substrate for the hexokinase reaction? Select two correct phrases. Mg2+ prevents ATP hydrolysis. Hexokinase cannot bind ATP when it is not complexed with Mg2+ . Mg2+ makes the ???? (terminal) phosphorus atom of ATP more accessible to electrophilic attack by a glucose –OH group. Mg2+ shields the negative charges of two of the phosphate oxygen atoms of ATP. Mg2+ makes the ???? (terminal) phosphorus atom of ATP more accessible to nucleophilic attack by a glucose –OH group.

Answer 1

Answer:

Mg is able to give off two of its electrons to other molecule, not four. ATP, in this case is the aceptor of those electrons

Two correct answers are:

1) Hexokinase cannot bind active ATP when it is not complexed with Mg2+

2) Mg2+ makes the terminal phosphorus atom of ATP more accessible to nucleophilic attack by a glucose-OH group

Explanation:

As Mg occurs naturally as ion Mg++, it is able to give off only two of its electrons to other molecule, then it is possible for ATP to receive two electrons of Mg, forming MgATP2-

The hexokinase reaction, here cited, corresponds to the glucose phosphorylation of its sixth carbon to produce glucose-6-P, which is a glycolysis intermediate. In this way glucose is activated (ATP is initially invested to energize glucose).  Later on, Glyceraldehide-3-P is produced, and finally converted to pyruvate, NADH2 and ATP