Catalyst — Science definition

Defined in 2 courses:

Where it is taught

In use

An enzyme is a biological catalyst: it dramatically speeds up a specific reaction, often by millions of times, without being used up in the process.

Enzymes

The fourth factor is a catalyst — a substance that speeds up a reaction without being consumed.

Reaction Rates & Kinetics

Questions using catalyst

Problem 1

An enzyme has the same reactant and product energy levels with and without a catalyst, but a lower pathway peak with it. Explain rate, equilibrium and energy implications.
Answer and explanation

The lower barrier can increase the approach rate in both directions. It does not by itself change the equilibrium or net free-energy change, and an unfavorable isolated process still needs suitable coupling or conditions.

The lower barrier can increase the approach rate in both directions. It does not by itself change the equilibrium or net free-energy change, and an unfavorable isolated process still needs suitable coupling or conditions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 2

Independent chapter check: An enzyme has the same reactant and product energy levels with and without a catalyst, but a lower pathway peak with it. Explain rate, equilibrium and energy implications.
Answer and explanation

The lower barrier can increase the approach rate in both directions. It does not by itself change the equilibrium or net free-energy change, and an unfavorable isolated process still needs suitable coupling or conditions.

The lower barrier can increase the approach rate in both directions. It does not by itself change the equilibrium or net free-energy change, and an unfavorable isolated process still needs suitable coupling or conditions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 3

Why does a catalyst not increase equilibrium yield solely by lowering activation barriers?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

It accelerates forward and reverse processes without changing the equilibrium constant at fixed temperature.

Problem 4

A catalyst speeds up a reaction by…
  1. raising the activation energy
  2. lowering the activation energy
  3. being used up quickly
  4. increasing ΔH
Answer and explanation

lowering the activation energy

A catalyst provides an alternate pathway with a lower activation energy, so more collisions are effective — and it is not consumed.

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