AnswersPA Human Anatomy Physiology A 2026-2027 SMITH ICCatalysts

Catalysts Answers

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1
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Which statement best describes how a catalyst can speed up a chemical reaction?

A
The catalyst decreases the activation energy needed.
B
The catalyst increases the concentration of products.
C
The catalyst binds to enzymes to release substrates.
D
The catalyst increases the concentration of reactants.
2
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Which is the best definition of activation energy?

A
the energy required to end a chemical reaction
B
the energy required to bind a substrate to an active site
C
the energy required to form or break the bonds of reactant molecules
D
the energy required to re-form bonds in product molecules
3

Photosynthesis is an example of

A
an exothermic reaction.
B
an endothermic reaction.
C
a reaction that gives off heat.
D
a reaction that emits energy.
4

Which term describes an enzyme?

A
substrate
B
reactant
C
catalyst
D
product
5

Which statement correctly describes a chemical reaction?

A
Reactants come out of a reaction.
B
Energy is always released.
C
Bonds between atoms break and reform.
D
Products go into a reaction.
6

Which two substances bind using a lock-and-key mechanism?

A
enzyme and substrate
B
reactant and substrate
C
substrate and product
D
reactant and product
7

The lock-and-key mechanism refers to

A
the complementary shapes of an enzyme and a substrate.
B
the attractive forces between an enzyme and a substrate.
C
the ability of an enzyme to lower the activation energy of a reaction.
D
the ability of an enzyme to “unlock” the products of a reaction.
8

A researcher is designing a laboratory experiment to determine whether the inorganic substance A affects the rate of a reaction between two colored liquids, X and Y. When the reaction is complete, the liquid is clear. The reaction between X and Y is similar to one used by manufacturers to produce certain chemicals in factories.Which method would best answer his question about reaction rate and what will he find out about substance A?

A
First, he should measure the final temperature of the liquid when X and Y react without substance A. Then, he should measure the final temperature when he adds substance A to X and Y. He will find out if substance A is a catalyst.
B
First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is a catalyst.
C
First, he should measure the final temperature of the liquid when X and Y react without substance A. Then, he should measure the final temperature when he adds substance A to X and Y. He will find out if substance A is an enzyme.
D
First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is an enzyme.
9

What must happen before a chemical reaction can begin?

A
The activation energy must be exceeded.
B
The activation energy must be reached.
C
The concentrations of products and reactants must be equal.
D
The concentration of reactant molecules must be reduced.
10

Lactase and carbonic anhydrase are examples of what type of substance?

A
substrate
B
reactant
C
product
D
enzyme
11

Which term describes an enzyme?

A
substrate
B
reactant
C
catalyst
D
product
12

Which statement best describes the amount of catalyst that remains at the end of a reaction?

A
More catalyst is present at the end than at the beginning of the reaction.
B
Less catalyst is present at the end than at the beginning of the reaction.
C
The amount of catalyst is the same at the end as at the beginning of the reaction.
D
The catalyst is consumed by the reaction, so none remains at the end of the reaction.
13

Lactase and carbonic anhydrase are examples of what type of substance?

A
substrate
B
reactant
C
product
D
enzyme
14

What must happen before a chemical reaction can begin?

A
The activation energy must be exceeded.
B
The activation energy must be reached.
C
The concentrations of products and reactants must be equal.
D
The concentration of reactant molecules must be reduced.
15

Which statement best describes how a catalyst can speed up a chemical reaction?

A
The catalyst decreases the activation energy needed.
B
The catalyst increases the concentration of products.
C
The catalyst binds to enzymes to release substrates.
D
The catalyst increases the concentration of reactants.
16

Which statement correctly describes a chemical reaction?

A
Reactants come out of a reaction.
B
Energy is always released.
C
Bonds between atoms break and reform.
D
Products go into a reaction.
17

What is a substrate?

A
a molecule that acts as a catalyst
B
a place on the enzyme where the reaction occurs
C
a place on the product where the enzyme fits
D
a reactant that is catalyzed by an enzyme
18

If the activation energy required for a chemical reaction were reduced, what would happen to the rate of the reaction?

A
The rate would increase.
B
The rate would decrease.
C
The rate would remain the same.
D
The rate would be zero.
19

Which two substances bind using a lock-and-key mechanism?

A
enzyme and substrate
B
reactant and substrate
C
substrate and product
D
reactant and product
20

How does a catalyst work?

A
by increasing the temperature of a chemical reaction
B
by decreasing the pressure of a chemical reaction
C
by increasing the concentration of reactants in a reaction
D
by decreasing the activation energy of a reaction

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