My AP Biology ThoughtsUnit 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...