8.2 Cell Respiration

Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics.

Paradigm shifts are something we see from time to time in biology but we also discuss them in TOK – they represent a way of looking at a problem from a completely new angle (van de Lagemaat).  In doing so, paradigm shifts can often be controversial and may take several years, or even decades, before they are accepted by the scientific community.

In 1961 Peter Mitchell proposed the chemiosmotic coupling theory to account for the production of ATP in oxidative phosphorylation. This theory went against the prevailing view that there were “energy-rich” chemical intermediates that explained the resulting ATP formation. As he writes in his landmark publication, from 1966,

“the study of the question of the coupling mechanism has continued to be ruled by the well-trodden and familiar tenets of the chemical coupling conception, no matter how fantastic the resulting tissue of hypothesis.” (Mitchell,1507)

Terms like “well-trodden” and “familiar” refer to the accepted theory that, despite results to the contrary, remains the only accepted explanation.  A paradigm shift must counter such ingrained views, which is why it can take time for the new explanation to become accepted.  Mitchell was awarded the Nobel Prize in Chemistry in 1978.  Part of his acceptance speech illustrates the challenges for the scientist trying to overturn entrenched theory:

 “…the originator of a theory may have a very lonely time, especially if his colleagues find his views of nature unfamiliar, and difficult to appreciate.” (“Peter Mitchell – Banquet Speech”)

There are many examples of paradigm shifts in biology – they make useful reference points for TOK discussion and analysis. Key terms to consider include bias, justification, subjective, objective and verification.


Mitchell, Peter. “Chemiosmotic coupling in oxidative and photosynthetic phosphorylation”.  Biochimica et Biophysica Acta (BBA) – Bioenergetics, Volume 1807, Issue 12, December 2011, Pages 1507-1538. Web. 19 April, 2016.

“Peter Mitchell – Banquet Speech”. Nobelprize.org. Nobel Media AB 2014. Web. 19 Apr 2016.

van de Lagemaat, R. Theory of Knowledge for the IB Diploma. Cambridge, Cambridge University Press. 2011. Print.