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

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 +
`$2ADP$`
`$\Delta G^0=2.1 \ kJ/mol$`