Study Notes on Enzymes and Catalysts

Enzymes and Catalysts

• Enzymes are proteins or RNA molecules that act as catalysts, increasing reaction rates without being consumed.

• They facilitate reactions by lowering activation energy barriers.

Key Concepts

• Activation Energy Barriers: Requires energy to reach transition states; spontaneous reactions may be slow due to high activation energy.

• Transition States: Unstable configurations that reactants must achieve during reactions.

• Enzymes change shape upon substrate binding through induced fit, optimizing interactions for catalysis.

Enzyme Activity

• Enzymes do not change Gibbs free energy (∆G); they can accelerate reactions but cannot convert non-spontaneous reactions into spontaneous ones.

• Enzymes exhibit specificity for substrates via active sites where substrate molecules bind.

• Activity is influenced by environmental conditions such as temperature and pH.

Regulation of Enzymes

• Cofactors: Non-protein helpers (e.g., vitamins) that enhance enzyme activity.

• Inhibitors:

  • Competitive inhibitors compete with substrates for active site binding.

  • Noncompetitive inhibitors alter enzyme shape without direct competition.

• Allosteric Regulation: Molecules bind to sites other than the active site, influencing activation state and activity.

Feedback Inhibition

• Inhibition of enzymatic pathways by the final product (e.g., ATP inhibits catabolic enzymes).

• This regulatory mechanism prevents overproduction of metabolites, maintaining cellular balance.