University Chemistry ›› 2019, Vol. 34 ›› Issue (4): 77-83.doi: 10.3866/PKU.DXHX201806016

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Discussion on the Definition of "Irreversible" Reactions and Its Related Concepts in Biochemistry

Xinyu MA1,Zhipeng A. WANG1,4,*(),Jie TIAN3,Zhenxiong JIANG3,Hanjie JIANG4,He SUN5,Qingxuan ZHOU6,Xin WANG2,*()   

  1. 1 Department of Chemistry, Texas A & M University, College Station, TX 77840, USA
    2 Department of Microbiology, Miami University, Oxford, OH 45056, USA
    3 Department of Biology, Texas A & M University, College Station, TX 77840, USA
    4 Division of Genetics, Department of Medicine, Brigham and Women's Hospital; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
    5 Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, Guangdong Province, P. R. China
    6 Broad Institute of MIT and Harvard, Cambridge; Department of Medicine, Harvard Medical School; Renal Division, Brigham and Women's Hospital, Boston, MA 02142, USA
  • Received:2018-06-15 Accepted:2018-07-17 Published:2019-04-28
  • Contact: Zhipeng A. WANG,Xin WANG;


Some of the enzyme catalysis reactions were classified as irreversible in the biochemistry education and research. However, it is worth noting that the "irreversibility" defined in biochemistry is different from what is referred in physical chemistry, which often confuses students. Consequently, the essence of irreversibility and its derivative may mislead students to a fallacious understanding towards the reaction process of biochemical reactions. This manuscript anew discusses the precise definition of "irreversible" reactions in biochemistry based on the standard definition of "irreversibility" given in physical chemistry, and we further use several terms and examples including rate limiting step, rate limiting enzyme, and high-energy phosphate bond to identify and correct misunderstandings caused by inaccurate definition of irreversibility.

Key words: Enzyme catalysis, Reversible reaction, Chemical equilibrium