Question

Write balanced equations for all the reactions in the catabolism of glucose to two molecules of glyceraldehyde 3-phosphate (the preparatory phase of glycolysis), including the standard free-energy change for each reaction. Then write the overall or net equation for the preparatory phase of glycolysis, with the net standard free-energy change.

Answer 1

Solution :

The balanced chemical equation are

The Catabolism of the glucose takes place in five stages :

1. Glucose + $ATP$ → glucose - $6$ - phosphate $+ ADP$  ,  $\Delta G^0=-16.7 \ kJ/mol$

2. Glucose - $6$ - phosphate → Fructose - $6$ - phosphate ,  $\Delta G^0=1.7 \ kJ/mol$

3. Glucose - $6$ - phosphate + $ATP$ → $ADP$ + Fructose - $1,6- \text{biophosphate}$,  $\Delta G^0=-14.2 \ kJ/mol$

4. Fructose - $1,6- \text{biophosphate}$  → dihydroxyacetonephosphate + glyceraldehyde  $-3 -$ phosphate,   $\Delta G^0=23.8 \ kJ/mol$

5. Dihydroxyacetonephosphate → glyceraldehyde  $-3 -$ phosphate , $\Delta G^0=7.5 \ kJ/mol$

Therefore, the overall net equations

Glucose + $2ATP \rightarrow$ glyceraldehyde  $-3 -$ phosphate + $2ADP$ $\Delta G^0=2.1 \ kJ/mol$