What is Enzyme Catalysis?
Enzyme catalysis is how enzymes speed up biochemical reactions by lowering the activation energy needed for substrates to turn into products. Nearly every reaction in a living cell depends on it, from digestion to DNA replication.
Enzyme catalysis is the process by which a protein enzyme binds a substrate at its active site and lowers the activation energy of a reaction, speeding it up thousands to millions of times without being consumed itself.
Try it: interactive calculator
Step-by-step worked examples
An enzyme has Vmax = 100 µM/min and Km = 10 µM. Find the rate when [S] = 10 µM.
v = Vmax×[S] / (Km+[S]) v = 100×10 / (10+10) v = 1000/20 = 50 µM/min (exactly half of Vmax, as expected when [S] = Km)
Same enzyme, [S] = 90 µM. Find the rate.
v = 100×90 / (10+90) v = 9000/100 = 90 µM/min
An enzyme reaches v = 40 µM/min when [S] = 5 µM and Km = 15 µM. Find Vmax.
40 = Vmax×5 / (15+5) 40 = Vmax×5/20 = 0.25×Vmax Vmax = 40/0.25 = 160 µM/min
Flashcards
Quick quiz
Q1.What does an enzyme do to a reaction's activation energy?
Q2.In v = Vmax[S]/(Km+[S]), what happens to v when [S] = Km?
Q3.Where does the substrate bind on an enzyme?
Q4.Is an enzyme consumed or permanently changed by the reaction it catalyzes?
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Common mistakes
Enzymes are used up during the reaction. — Correct: Enzymes are reused — they are not consumed, only the substrate is converted to product.
Enzymes make impossible reactions possible. — Correct: Enzymes only speed up reactions that are already thermodynamically favorable; they don't change the equilibrium.
Higher temperature always increases enzyme activity. — Correct: Activity rises with temperature only up to an optimum — beyond it the enzyme denatures and activity crashes.
All enzymes work best at pH 7. — Correct: Optimal pH varies by enzyme — pepsin works best around pH 2, for example.
FAQ
What is enzyme catalysis?
It is the speeding up of a biochemical reaction by an enzyme, which lowers the activation energy required, often by a factor of a million or more.
What is the enzyme catalysis formula?
The Michaelis-Menten equation, v = Vmax[S]/(Km+[S]), relates reaction rate to substrate concentration.
What are examples of enzyme catalysis?
Amylase breaking down starch in saliva, catalase decomposing hydrogen peroxide, and DNA polymerase copying DNA are all everyday examples.
How do you calculate enzyme reaction rate?
Plug substrate concentration, Vmax, and Km into v = Vmax[S]/(Km+[S]), or use the interactive calculator above.