Threshold concepts

What are threshold concepts?
Threshold concepts are concepts and skills that, when mastered, represent a transformed understanding of a discipline, without which the learner cannot progress. The TCs framework has a record of promoting curricular realignment aimed at prioritizing the most important and difficult concepts within a discipline and is a valuable tool to promote transformation in STEM education. The TC process has proven to be an exciting and accessible mechanism to engage faculty members, putting their disciplinary expertise at the forefront.

What threshold concepts have been identified for biochemistry and molecular biology?
We identified five TCs for biochemistry and molecular biology through a collaborative effort involving over 70 faculty members and 50 undergraduate students at five diverse institutions. Three major sources of information were used to identify threshold concepts for biochemistry: faculty member workshops, student interviews and existing data from the literature and other sources. A brief description of the TCs is given below; a complete description of the process used to identify threshold concepts was published in Life Sciences Education.

  • Steady state: Living organisms constitute open systems, which constantly exchange matter and energy with their surroundings; yet, net concentrations remain relatively constant over time. This dynamic, yet outwardly stable condition, is referred to as a steady state. Steady state defines the conditions of life under which chemical reactions take place in cells and organisms.
  • Biochemical pathway dynamics and regulation: Reactions and interactions in biological systems are dynamic and reversible. Chemical drivers result in the emergent properties observed in biological systems. Enzyme-mediated regulatory mechanisms allow pathways to be sensitive and responsive to the needs of the organism.
  • The physical basis of interactions: Interactions occur because of the electrostatic properties of molecules. These properties can involve full, partial, and/or momentary charges. Correct understanding of noncovalent interactions is essential in integrating structure and function.
  • Thermodynamics of macromolecular structure formation: Protein folding, the assembly of lipids into micelles and bilayers, the association of polypeptide subunits to form oligomeric proteins, base pairing of DNA and RNA molecules, and all other biological interactions are driven by a common set of thermodynamic forces. The aqueous environment of the cell plays an active and essential role in biochemical structure formation.
  • Free energy: Differences in free energy drive the chemical transformations underlying biological function. By providing a direct link between a thermodynamically-favorable reaction with a thermodynamically-unfavorable one, enzymes enable biological systems to drive a normally unfavorable reaction by coupling it to one with a large and favorable free energy change.

What resources are available for teaching and assessing BMB threshold concepts?
Efforts are underway to develop instructional materials and assessment instruments for these TCs. Data collected from pilot studies at diverse institutions in the U.S. will be used in a feedback loop to revise instructional and assessment materials and improve teaching and learning in undergraduate BMB courses.

How do I learn more?
If you would like additional information, have questions or want to be involved in testing new materials as they are developed, please contact the ASBMB education department (

Project support
This work is supported by a National Science Foundation grant (NSF-DUE #1224868) to Vicky Minderhout and Jenny Loertscher. This page contains excerpts from Life Sciences Education, which were reproduced with permission from the publisher.