Study guides › B/B › Biochemistry
Enzymes & Kinetics
Enzymes speed up nearly every reaction in the cell. You will learn how they catalyze, how to read Michaelis-Menten and Lineweaver-Burk plots, how each inhibitor type changes Km and Vmax, and how enzymes are regulated and classified.
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What this chapter covers
- How Enzymes Catalyze Reactions. Enzymes change how fast a reaction reaches equilibrium, never where equilibrium lies. That single idea answers many MCAT traps.
- Michaelis-Menten Kinetics. Km and Vmax are the two numbers you must be able to read off a curve and interpret on Test Day.
- Lineweaver-Burk Plots & Inhibition. Every inhibitor type has a signature on a double-reciprocal plot, and the MCAT expects you to match them.
- Allosteric & Covalent Regulation. Cells switch enzymes on and off in seconds using allostery, phosphorylation, and zymogens, and each mechanism has its own signature.
- Enzyme Classes, Cofactors & Environment. Classify the enzyme from its name, identify the vitamin behind the coenzyme, and predict how pH and temperature change activity.
Key points to know
- Enzymes lower Ea by stabilizing the transition state
- They do not change ΔG, Keq, or the equilibrium position
- Km = [S] at half Vmax; low Km means high affinity
- Vmax = kcat[E]total; more enzyme raises Vmax, not Km
- LB: y-intercept 1/Vmax, x-intercept −1/Km, slope Km/Vmax
- Competitive: Vmax same, Km up, lines cross on the y-axis
- Allosteric enzymes give sigmoidal v vs [S] and are multi-subunit
- Activators shift the curve left; inhibitors shift it right
Try a practice question
How does an enzyme increase the rate of a reaction?
- By making ΔG more negative
- By shifting the equilibrium toward products
- By lowering the activation energy
- By raising the energy of the reactants
Show the answer
C. Enzymes stabilize the transition state, reducing Ea. ΔG and the equilibrium position are properties of reactants and products and do not change.
Common questions
What does this chapter cover?
Enzymes & Kinetics covers How Enzymes Catalyze Reactions, Michaelis-Menten Kinetics, Lineweaver-Burk Plots & Inhibition, Allosteric & Covalent Regulation, Enzyme Classes, Cofactors & Environment.
What should I know first?
Enzymes lower Ea by stabilizing the transition state They do not change ΔG, Keq, or the equilibrium position Km = [S] at half Vmax; low Km means high affinity
24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.