Ok, this question seems like it may be impossible to answer, but would be interesting to see if anyone has an idea.

Throughout the course of a human life, do we make more molecular bonds than we break, or vice versa?


1 Answer 1


Metabolism ≈ Anabolism + catabolism

Metabolism is the set of all chemical reactions happening inside a living body. These reactions can either breaks down big molecules and build up big molecules. The set of reactions the breaks down big molecules is called catabolism. The set of reactions that build up big molecules is called anabolism.


Generally speaking, anabolism cost energy and catabolism yield energy. The molecule that is directly used to transfer this energy is Adenosine triphosphate (ATP).

Any energy transfer is coupled with some loss of energy from the system (see Energy conversion efficiency).


For any chemical reactions, there is always an overall increase of entropy. As a consequence, a living organism increases the entropy in its surrounding. In other words, it breaks more than it builds.

Your question

does life make or break?

Life does both! But on average, it mainly breaks things up (just like any other chemical reaction).

Want to learn more?

The concepts of energy and entropy are studied in physics and chemistry but not so much in biology. I cannot really give you a good source of information.

Khan Academy offers a very good introductory course on metabolism (here), you should have a look!

  • $\begingroup$ that's a great answer, thankyou. But if the breaking of molecular bonds is endothermic, and life 'mainly breaks things up', does that mean life is negative entropy? masterorganicchemistry.com/2010/10/28/… $\endgroup$
    – Amphibio
    Mar 11, 2016 at 0:30
  • $\begingroup$ My guess would be that, as complex organisms, we make more complex molecules than we break ---> net exothermic ---> entropy $\endgroup$
    – Amphibio
    Mar 11, 2016 at 0:36

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