Enzymes

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Chemical Reaction Noun

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[kem-i-kuhl ree-ak-shun]

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Chemical Reaction

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A process that changes one set of chemical substances into another by rearranging their constituent atoms.

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Example: This image shows how atoms in starting molecules (reactants like methane and oxygen) rearrange to form new molecules (products like carbon dioxide and water).

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Reactant Noun

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[ree-ak-tunt]

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Reactant

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A substance that enters into and is altered during the course of a chemical reaction.

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Example: This diagram shows that reactants, like sodium (Na) and water (H2O), are the starting materials in a chemical reaction that are consumed to form new products.

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Product Noun

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[prod-ukt]

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Product

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A chemical substance that is formed as the result of a chemical reaction between reactants.

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Example: In a chemical reaction, reactants (left) are changed into new substances called products (right), like the CO2 and H2O molecules shown here.

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Catalyst Noun

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[kat-uh-list]

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Catalyst

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A substance that increases the rate of a chemical reaction without being consumed in the process.

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Example: This graph shows that a chemical reaction with a catalyst requires less activation energy (a smaller hill to climb) than a reaction without one.

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Enzyme Noun

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[en-zahym]

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Enzyme

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A protein that acts as a biological catalyst to accelerate biochemical reactions within a living organism.

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Example: An enzyme binds specific molecules called substrates at its active site, changes them into a new product, and then releases the product, remaining unchanged.

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Substrate Noun

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[suhb-streyt]

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Substrate

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The specific molecule upon which an enzyme acts to facilitate a chemical reaction.

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Example: This diagram shows a substrate, the specific molecule that an enzyme acts on. The substrate's unique shape allows it to fit perfectly into the enzyme's active site, like a key fitting into a lock.

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Active Site Noun

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[ak-tiv sahyt]

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Active Site

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The specific region of an enzyme where the substrate binds and the chemical reaction is catalyzed.

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Example: This diagram shows that the active site is the specific part of an enzyme that has a unique shape to fit and bind with a matching substrate.

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Activation Energy Noun

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[ak-tuh-vey-shuhn en-er-jee]

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Activation Energy

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The minimum amount of energy that must be provided for a chemical reaction to occur.

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Example: This graph shows that enzymes act as catalysts by lowering the activation energy (the 'hill') needed for a reaction, making it happen more easily.

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Specificity Noun

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[spes-uh-fis-i-tee]

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Specificity

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The characteristic of an enzyme to catalyze only one or a very limited range of chemical reactions.

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Example: This image shows that an enzyme has a specifically shaped active site, like a lock, that only fits a specific substrate, like a key.

Front

Lock-and-Key Model Noun

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[lok and kee mod-l]

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Lock-and-Key Model

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A model of enzyme action where the substrate fits perfectly into a rigid, pre-shaped active site.

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Example: This diagram shows how a specific substrate (key) fits perfectly into the active site of an enzyme (lock), forming a complex and then releasing new products.