Energy, Enzymes, and Biological Reactions

An enzyme serves as a place where a chemical reaction can occur because-

• the enzyme is a substrate.
• the enzyme is one of the reactants in the reaction.
• the charge on the enzyme's active site is the same as the charge on the substrates.
• the shape of the substrates fits perfectly into the shape of the enzyme's active site.

Most enzymes work best at about 37°C, normal body temperature, and each one

• is usually specific to only one type of chemical reaction in the body.
• serves as a catalyst for several kinds of reactions.
• helps speed up reactions by a factor of 2.
• helps slow down reactions by a factor of 10.

An enzyme acts as a catalyst to a chemical reaction by

• lowering the activation energy needed to get the reaction started.
• making one of the substrates needed for the reaction.
• regulating the temperature at which the reaction takes place.
• regulating the pH at which the reaction takes place.

How do enzymes control chemical reactions in the body?

• Enzymes speed up chemical reactions.
• Enzymes slow down chemical reactions.
• Enzymes increase the activation energy of a reaction.
• Enzymes inhibit the catalysts of a reaction.

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Enzymes are proteins that are found in cells. What is their role?

• They speed up chemical reactions in cells.
• They lower the activation energy needed for some reactions.
• They regulate the absorption of energy in chemical reactions.
• All the other answers are correct.

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Enzymes provide a site where reactants called substrates can be brought together in an enzyme-catalyzed reaction. The site is called the

• enzyme substrate complex.
• reaction site.
• active site.
• lock and key.

Chemical reactions always involve

• the breaking of bonds in reactants.
• the formation of new bonds in products.
• the breaking of bonds in reactants and the formation of new bonds in products.
• enzymes. 

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In a chemical reaction, a reactant binds to an enzyme at a region known as the

• catalyst.
• product.
• substrate.
• active site. 

An enzyme speeds up a reaction by

• lowering the activation energy.
• raising the activation energy.
• releasing energy.
• absorbing energy.

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The substances that are present before a reaction are the...

• reactants
• products
• both of these
• neither of these