Enzyme Kinetics: The Basics | Michaelis–Menten, Km, Vmax & kcat

You have three drinks at a party. Your best friend has six. Will their liver work twice as fast? No. Both work at roughly the same rate. Your friend simply takes longer. Why? Let's find out! 🧪 WHAT YOU'LL LEARN • What an enzyme's reaction rate means, and why we measure its initial rate • How measurements from test tubes become the Michaelis–Menten curve • Saturation: why the curve levels off, and what Vmax means • kcat, the turnover number: from catalase to RecA • Km: the substrate concentration at half the maximum rate—and why it doesn't always mean “affinity” • Catalytic efficiency, kcat/Km, and the diffusion limit • Lineweaver–Burk plots: why scientists took reciprocals, and the cost of straightening the curve • Why alcohol dehydrogenase in your liver works close to its maximum rate ⏱️ CHAPTERS 0:00 Three drinks versus six: the party 0:43 Measuring an enzyme's reaction rate 1:31 Focus on the start: initial rate 2:05 From test tubes to the curve 2:45 Saturation: why the curve levels off (Vmax) 3:33 More enzyme, a higher ceiling (kcat) 4:23 Km: the substrate concentration at half the maximum rate 5:23 Km doesn't always mean affinity 6:12 1913: the story behind the curve 6:52 Efficiency: kcat/Km and the diffusion limit 7:39 The cost of straightening the curve (Lineweaver–Burk) 8:30 The complete equation—and the party explained 📄 SOURCES The textbook: Nelson D. L., Cox M. M., Hoskins A. A. Lehninger Principles of Biochemistry. 8th edition. Macmillan International Higher Education, 2021. The original article (no verified DOI): Michaelis L., Menten M. L. (1913). Die Kinetik der Invertinwirkung. Biochemische Zeitschrift 49:333–369. Its translation and reanalysis: Johnson K. A., Goody R. S. (2011). The Original Michaelis Constant: Translation of the 1913 Michaelis–Menten Paper. Biochemistry. https://doi.org/10.1021/bi201284u pH, buffers, and Victor Henri: Gunawardena J. (2012). Some lessons about models from Michaelis and Menten. Molecular Biology of the Cell. https://doi.org/10.1091/mbc.e11-07-0643 Maud Menten: Wright J. R. (2023). Maud Menten: Pioneering Pediatric-Perinatal Pathologist, Clinician-Scientist, and “the Most Wonderful Human Being in the World”. Pediatric and Developmental Pathology. https://doi.org/10.1177/1093526623120... Andersch M. A., Wilson D. A., Menten M. L. (1944). Sedimentation constants and electrophoretic mobilities of adult and fetal carbonylhemoglobin. Journal of Biological Chemistry. https://doi.org/10.1016/s0021-9258(18... The double-reciprocal plot and direct curve fitting: Lineweaver H., Burk D. (1934). The Determination of Enzyme Dissociation Constants. Journal of the American Chemical Society. https://doi.org/10.1021/ja01318a036 Johnson K. A. (2019). New standards for collecting and fitting steady state kinetic data. Beilstein Journal of Organic Chemistry. https://doi.org/10.3762/bjoc.15.2 Acetylcholinesterase at the neuromuscular junction: Campanari M.-L. et al. (2016). Neuromuscular Junction Impairment in Amyotrophic Lateral Sclerosis: Reassessing the Role of Acetylcholinesterase. Frontiers in Molecular Neuroscience. https://doi.org/10.3389/fnmol.2016.00160 Alcohol and your liver: Edenberg H. J. (2007). The genetics of alcohol metabolism: role of alcohol dehydrogenase and aldehyde dehydrogenase variants. Alcohol Research & Health. PMID 17718394. https://pubmed.ncbi.nlm.nih.gov/17718... Jones A. W. (2010). Evidence-based survey of the elimination rates of ethanol from blood with applications in forensic casework. Forensic Science International. https://doi.org/10.1016/j.forsciint.2... Methanol and its antidote: Mégarbane B. (2010). Treatment of patients with ethylene glycol or methanol poisoning: focus on fomepizole. Open Access Emergency Medicine. https://doi.org/10.2147/oaem.s5346 Pan American Health Organization/World Health Organization. Epidemiological Alert: Methanol poisoning risk. 7 October 2025. PAHO/WHO. https://www.paho.org/sites/default/fi... Learn, and become your best version. Make Things Viral — @makethingsviral Find me on my socials: Instagram and Facebook — @brandonortizcasas #Biochemistry #Enzymes #EnzymeKinetics #MichaelisMenten #Science