Summary
Reactions proceed spontaneously when the change in Gibbs free energy is negative; ATP hydrolysis drives unfavourable ones.
In depth
Gibbs free energy change equals ΔH minus TΔS. Negative ΔG reactions are exergonic and can proceed; positive ones are endergonic. Coupling links an unfavourable reaction to ATP hydrolysis (about -30.5 kJ per mole under standard conditions, more in cells).
Equilibrium has ΔG zero, and living cells are kept far from equilibrium by continuous input of energy.
Key idea: life maintains order locally by increasing entropy elsewhere.
Frequently asked questions
What is Free Energy in Biology?
Reactions proceed spontaneously when the change in Gibbs free energy is negative; ATP hydrolysis drives unfavourable ones.
Which area of biology covers Free Energy in Biology, and how advanced is it?
Free Energy in Biology is one of the 51 topics in Biomolecules & Biochemistry. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Activation Energy, Enzymes, Macromolecules.
What should I learn before Free Energy in Biology?
Work through the Beginner topics in Biomolecules & Biochemistry first, such as Water Properties, Carbon Chemistry, Carbohydrates, then return to Free Energy in Biology. Advanced topics assume the Intermediate vocabulary.
What topics are related to Free Energy in Biology?
The closest topics to Free Energy in Biology are Activation Energy, Enzymes, Macromolecules, pH and Buffers. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Free Energy in Biology?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Free Energy in Biology. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Free Energy in Biology different from Activation Energy?
Free Energy in Biology: Reactions proceed spontaneously when the change in Gibbs free energy is negative; ATP hydrolysis drives unfavourable ones. Activation Energy: The minimum energy needed to start a reaction, lowered by enzymes without changing the overall energy change. Read both side by side and note what each one explains.
How should I study Free Energy in Biology step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Activation Energy and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.