Question

This application demonstrates how an understanding of free energy can explain seemingly unfavorable reactions proceeding, seemingly, spontaneously. Glycolysis is the process by which energy is harvested from glucose by living things. Several of the reactions of glycolysis are thermodynamically unfavorable (nonspontaneous), but proceed when they are coupled with other reactions. Reaction A: P i + glucose ⟶ glucose-6-phosphate + H 2 O Δ G = 13.8 kJ / mol Reaction B: P i + fructose-6-phosphate ⟶ fructose-1,6-bisphosphate + H 2 O Δ G = 16.3 kJ / mol Reaction C: ATP + H 2 O ⟶ ADP + P i Δ G = − 30.5 kJ / mol

Answer 1

Glycolysis is an essential energy-harvesting pathway where thermodynamically unfavorable reactions proceed due to coupling with the energetically favorable hydrolysis of ATP, resulting in a spontaneous overall pathway and the production of ATP.

Step-by-step explanation:

Glycolysis is a fundamental metabolic pathway used in the breakdown of glucose to harvest energy.

Throughout this pathway, several reactions are considered thermodynamically unfavorable or nonspontaneous. However, these reactions can still proceed because they are coupled with the hydrolysis of ATP, an energetically favorable (exergonic) reaction, which provides the necessary energy to drive them forward.

In the first step of glycolysis, ATP hydrolysis is coupled with the phosphorylation of glucose to form glucose-6-phosphate, a high-energy and unstable intermediate.

This is despite the fact that individual steps, such as the conversion of glucose to glucose-6-phosphate (Reaction A) and fructose-6-phosphate to fructose-1,6-bisphosphate (Reaction B), have a positive change in free energy (ΔG). The coupling with ATP hydrolysis (Reaction C), which has a negative ΔG, makes the overall pathway spontaneous.

Ultimately, this results in the production of pyruvate and the synthesis of ATP, demonstrating how free energy calculations can explain the spontaneous nature of glycolysis in living cells. The fact that this pathway is universal among organisms suggests its evolutionary significance.

Answer 2

Answer: your question is incomplete, please let me assume this to be your question.

This application demonstrates how an understanding of free energy can explain seemingly unfavorable reactions proceeding, seemingly, spontaneously. Glycolysis is the process by which energy is harvested from glucose by living things. Several of the reactions of glycolysis are thermodynamically unfavorable (nonspontaneous), but proceed when they are coupled with other reactions.

ReactionA: P i + glucose ⟶ glucose-6-phosphate + H 2 O Δ G = 13.8 kJ / mol Reaction

ReactionB: P i + fructose-6-phosphate ⟶ fructose-1,6-bisphosphate + H 2 O Δ G = 16.3 kJ / mol

Reaction C: ATP + H 2 O ⟶ ADP + P i Δ G = − 30.5 kJ / mol

1. Which of these reactions is (are) unfavorable? Select all that apply.

2. Which of these reactions can be coupled so that overall reaction is favorable? Select all that apply.

3. What is the net change in free energy if one selection from part (b) is coupled so that the overall reaction is favorable?

THE ANSWERS ARE AS FOLLOWS

1. REACTION B IS UNFAVOURABLE

2. REACTION A AND C CAN BE COUPLED SO THAT OVERALL REACTION IS FAVOURABLE

3. Since reaction b is coupled the net change becomes

13.8+16.3= 30.1

Therefore the net free change becomes

30.5 - 30.1 = 0.4kj/mol

Explanation: The glycolysis pathway

is to describe the oxidation of glucose to pyruvate, with the generation of ATP and NADH. This pathway is also known as the EMBDEN-MEYERHOF PATHWAY.

Reaction B is unfavorable because it is the conversation of glucose into an unstable form, that can be readily cleaved into 3-carbon units. The unfavorable fructose-6-phosphate is quickly consumed to favour the forward reaction.

Reaction A and Reaction C makes the overall reaction to be favoured, since the unfavorable reaction is reaction B, which is an intermediate reaction.

In calculation of net free energy the negative sign which shows Exothermic reaction is multiplied by a negative sign.

The final energy minus the initial energy. The reaction B is added to the initial energy because it is an intermediate reaction, and we were told that one part of it is coupled to the reaction.

Hope this has helped you to solve your question.