Enzyme — Science definition

Defined in 2 courses:

Where it is taught

In use

That something is an enzyme, and the distinction Beaumont glimpsed is the backbone of this unit.

Digestion, Absorption & Food Molecules

The reason you're not waiting years to digest lunch is biological catalysts called enzymes, most of which are proteins; some RNA molecules also catalyze reactions and are called ribozymes.

Enzymes

Questions using enzyme

Problem 1

Illustrative comparison: Sample A remains in one large piece; equal-mass Sample B is divided into small pieces. Both experience the same stated enzyme conditions; B breaks down faster. Explain a surface-area mechanism, distinguish observation from inference, and connect digestion with absorption.
Answer and explanation

Faster breakdown in B is consistent with increased exposed surface for enzyme contact under the stated conditions. The result is evidence about breakdown rate, not proof that absorption or energy use has already occurred. Further measurements could check the products and their passage across an exchange surface. Other changed conditions would weaken the isolated surface-area explanation.

Identify comparable mass and conditions.

Connect smaller pieces with more exposed surface.

Separate breakdown from later boundary crossing.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 2

An enzyme is best described as a
  1. protein that speeds up a chemical reaction without being used up
  2. sugar that stores energy for the cell
  3. type of lipid that builds the cell membrane
  4. molecule that stores genetic information
Answer and explanation

protein that speeds up a chemical reaction without being used up

Enzymes are protein catalysts — they speed up specific reactions and are not consumed, so they can be reused.

Problem 3

The specific molecule that an enzyme acts on is called its
  1. active site
  2. substrate
  3. product
  4. catalyst
Answer and explanation

substrate

The substrate is the molecule that binds the active site and gets changed into product.

Problem 4

Why does an enzyme stop working at very high temperatures?
  1. The substrate becomes too cold to move
  2. High heat gives the enzyme an extra active site
  3. The heat denatures the enzyme, changing the shape of its active site so the substrate no longer fits
  4. The enzyme is used up in the reaction
Answer and explanation

The heat denatures the enzyme, changing the shape of its active site so the substrate no longer fits

Too much heat unravels the protein's folding (denaturing), distorting the active site so the substrate can't bind.

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