## Positive Gibbs Free Energy

$\Delta G^{\circ}= \Delta H^{\circ} - T \Delta S^{\circ}$

$\Delta G^{\circ}= -RT\ln K$

$\Delta G^{\circ}= \sum \Delta G_{f}^{\circ}(products) - \sum \Delta G_{f}^{\circ}(reactants)$

megansardina2G
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### Positive Gibbs Free Energy

How are reactions that have a positive ∆G carried out, as they are not spontaneous? (Especially in biological systems)

anthony_trieu2L
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

### Re: Positive Gibbs Free Energy

Reactions with a positive Gibbs free energy are usually carried out with accompaniment of another reaction. This is called a coupled reaction, and it allows the overall process to occur. An example is ATP hydrolysis, in which ATP is used to carry out the main reaction.

Sarah Zhao 4C
Posts: 64
Joined: Fri Sep 28, 2018 12:28 am

### Re: Positive Gibbs Free Energy

Non-spontaneous does not mean that it cannot happen. It rather means that it requires an input of energy to happen.

GavinAleshire1L
Posts: 29
Joined: Fri Sep 28, 2018 12:21 am

### Re: Positive Gibbs Free Energy

Like stated above, reactions with positive delta G usually involve coupling with ATP hydrolysis in order to carry out an anabolic reaction where the reactants form a higher energy product. These reactions are called endergonic. Another example of a reaction like this is photosynthesis which utilizes light energy instead of ATP to build glucose.

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