Endergonic and Exergonic Reactions
My AP Biology Thoughts
Unit 3 Cellular Energetics
Welcome to My AP Biology Thoughts podcast, my name is Nikki and I am your host for episode #67 called Unit 3 Cellular Energetics: endergonic and exergonic rxn. Today we will be discussing the differences between endergonic and exergonic reactions and how they play a role in metabolic processes.
Segment 1: Introduction to endergonic and exergonic rxn
● Exergonic
○ Release energy
○ Products have less free E than reactants
○ Energetically downhill
○ Tend to be spontaneous
○ Tend to be catabolic aka break down rxn
○ Delta G is neg
■ Remember delta g is free energy aka usable energy
● Endergonic
○ Absorb energy
○ Products have more free E than reactants
○ Energetically uphill
○ Tend to not be spontaneous
○ Tend to be anabolic aka create
○ Delta G is pos
Segment 2: More About endergonic and exergonic rxn
● Example of endergonic rxn
○ Dehydration synthesis
○ Combining molecules
○ Release water
○ Take in energy
● Example of exergonic rxn
○ Hydrolysis of ATP
○ Breaking apart molecules
○ Water molecule is taken in
○ More energy out of system
○ Releases energy
Segment 3: Connection to the Course
● There is a series of intermediate reactions that form a metabolic pathway
● While enzymes play a role in these reactions, an important concept that connects exergonic and
endergonic reactions is coupled reactions
○ This is when a catabolic reaction that breaks down something is coupled with a reaction that
makes something
○ Let’s remember that endergonic reactions are usually anabolic exergonic reactions are usually
catabolic
● So in the case of ATP hydrolysis, E is released by the exergonic rxn because remember the bonds are
being broken so E is released and this energy can now go and drive an endergonic reaction
● This coupling of reactions plays a big role in the intermediate reactions that form metabolic pathways
Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
Music Credits:
● “Ice Flow” Kevin MacLeod (incompetech.com)
● Licensed under Creative Commons: By Attribution 4.0 License
● http://creativecommons.org/licenses/by/4.0/
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