Chemical Reactions and 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 transforms one set of chemical compounds into another by changing the chemical bonds joining the atoms.

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Example: Reactants (like methane and oxygen) are starting materials whose atoms rearrange to form new substances called products (like carbon dioxide and water).

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Reactant Noun

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[ree-ak-tant]

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Reactant

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An element or compound that engages in and is consumed during the course of a chemical reaction.

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Example: The image shows hydrogen (H₂) and oxygen (O₂) on the left, which are the reactants that combine in a chemical reaction to form water (H₂O).

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Product Noun

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[prod-ukt]

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Product

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An element or compound that is formed as the result of a completed chemical reaction.

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Example: In a chemical reaction, the starting materials (reactants) are transformed into new substances called products, shown here as carbon dioxide and water.

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Activation Energy Noun

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

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Activation Energy

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The minimum amount of energy that must be provided for compounds to react and start a chemical reaction.

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Example: This graph shows that reactants need a boost of energy, called activation energy, to climb an 'energy hill' before they can become products.

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Catalyst Noun

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[kat-l-ist]

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Catalyst

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A substance that increases the rate of a chemical reaction by lowering its activation energy without being consumed itself.

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Example: A catalytic converter uses a catalyst to speed up the chemical reaction that changes harmful car exhaust gases into safer substances like carbon dioxide.

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Enzyme Noun

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[en-zahym]

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Enzyme

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A specialized protein that acts as a biological catalyst to accelerate chemical reactions within living organisms' cells.

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Example: This diagram shows an enzyme binding to a specific substrate at its active site, changing the substrate into products, and then releasing them, ready to work again.

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Substrate Noun

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[suhb-streyt]

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Substrate

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The specific reactant molecule that an enzyme binds to and acts upon during a catalyzed chemical reaction.

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Example: The substrate is a molecule that fits perfectly into the active site of an enzyme, like a key in a lock, to form an enzyme-substrate complex.

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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 on an enzyme's surface where substrate molecules bind and the chemical reaction takes place.

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Example: This diagram shows how an enzyme has a specifically shaped area, the active site, that fits a corresponding substrate, like a key fitting into a lock.

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Enzyme-Substrate Complex Noun

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[en-zahym suhb-streyt kom-pleks]

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Enzyme-Substrate Complex

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The temporary structure formed when a substrate molecule binds to the active site of an enzyme before being converted.

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Example: This diagram shows a green substrate molecule fitting perfectly into the active site of a yellow enzyme, forming a temporary structure called the enzyme-substrate complex.