Name _______________________________________
Date _______________
Enzymes and Chemical Reactions
Homework/Study Guide
Directions: Below you will find a variety of questions on enzymes and the chemical reactions of the cell. As
you will soon notice, the questions are of varying formats. For short answer questions, please
write in complete sentences. For true/false questions, first determine if the statement is true or
false. If the statement is false, correct the underlined word to make the statement true.
Compare and Contrast the following pairs of terms:
1.
Reactant / Product: ____________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
2.
Enzyme / Catalyst: ____________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Short Answer Questions:
3.
Explain what happens to chemical bonds during the course of a chemical reaction.
4.
What role does energy play in a chemical reaction?
5.
What role do enzymes play within living cells?
1
6.
What would happen if enzymes were not present inside cells?
7.
Why is it essential that energy-releasing reactions take place inside living cells?
8.
What is activation energy?
9.
How does an enzyme speed up a chemical reaction?
10.
Do all chemical reactions require activation energy? Explain.
Fill in the Blank:
________________________11.
What name is given to the reactants of an enzyme-catalyzed reaction?
________________________12.
What is the name of the indentation on the surface of an enzyme into which
the substrate molecules must fit?
A new and different molecule formed as a result of a chemical reaction is
called the ____?
The process that converts or changes one set of chemicals into a new and
different set of chemicals is called a _____?
This term means that the enzyme shape has been altered and it will no
longer match the shape of its substrate.
What analogy is often used to describe the precise fit between an enzyme
and its substrate?
Enzymes speed up chemical reactions by lowering the _____ of the
reaction.
List two factors that would affect the activity of enzymes.
________________________13.
________________________14.
________________________15.
________________________16.
________________________17.
________________________18.
2
________________________19.
The energy needed to start a chemical reaction is called ______.
________________________20.
The binding together of an enzyme and a substrate molecule forms a(n)
______.
Enzymes make reactions take place __21__ and at lower __22__.
________________________21.
________________________22.
________________________23.
What is the optimum temperature for enzyme functioning for most
enzymes?
Multiple Choice:
________24. How does an enzyme speed up a chemical reaction?
(a) It raises the activation energy.
(b) It lowers the activation energy.
(c) They release energy.
(d) They absorb energy.
________25. Enzymes belong to which group of organic compounds?
(a) carbohydrates (b) lipids (c) proteins (d) nucleic acids.
________26. Which of the following is not true about enzymes?
(a) Enzymes are proteins. (b) Enzymes require water in order to function. (c) Enzymes are
rarely affected by heat or pH. (d) Enzymes are specific for just one reaction.
True or False. Determine if the statement is true or false. If the statement is false, correct
the underlined word to make the statement true.
_________________27.
_________________29.
Enzymes are biological hormones that help to speed up the chemical reactions of the
cell.
Chemical reactions involve changes in the chemical bonds that join atoms together
in compounds.
Inside cells, chemical reactions require energy, but never release energy.
_________________30.
Starting a chemical reaction requires activation energy.
_________________31.
Enzymes are very versatile and can be used in many different types of reactions.
_________________32.
_________________33.
The activation energy is usually in the form of heat that the reactant molecules
absorb from their surroundings.
Most enzymes function best at a pH range of 6 – 8.
_________________34.
Catalysts are affect by temperature and pH just as enzymes are.
_________________35.
Neither enzymes nor catalysts are consumed in the reaction and may be used again.
_________________36.
If two reactants fail to react with one another, the addition of the enzyme will force
them to react.
_________________28.
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37.
38.
39.
40.
This diagram can be used to represent an enzymatic reaction. Label each part of the equation. Use the
equation to write a short description about how enzymes work.
Explain what has happened if an enzyme has become “denatured.”
Using the above diagram as a guide, draw a simple diagram showing what would happen if the
enzyme became denatured.
What might cause an enzyme to denature?
Copyright © January 2012 Amy Brown (aka Science Stuff)
4
Name _______________________________________
Date _______________
Enzymes and Chemical Reactions
Homework/Study Guide
Answer Key
Directions: Below you will find a variety of questions on enzymes and the chemical reactions of the cell. As
you will soon notice, the questions are of varying formats. For short answer questions, please
write in complete sentences. For true/false questions, first determine if the statement is true or
false. If the statement is false, correct the underlined word to make the statement true.
Compare and Contrast the following pairs of terms:
1.
Reactant / Product: Reactants are the elements or compounds that enter into a chemical reaction.
Products are the elements or compounds that are produced as a result of the chemical reaction.
2.
Enzyme / Catalyst: Both substances speed up the rate of a chemical reaction. Catalysts are inorganic
substances, while enzymes are organic substances (proteins).
Short Answer Questions:
3.
Explain what happens to chemical bonds during the course of a chemical reaction.
During the chemical reaction, the bonds are broken in the reactant molecules. New bonds are formed to
produce the products.
4.
What role does energy play in a chemical reaction?
Some chemical reactions absorb energy, while other reactions release energy. This change in energy
between the reactants and the products determines how easily a particular reaction will occur.
5.
What role do enzymes play within living cells? Enzymes speed up the chemical reactions within the cell.
These reactions would take place on their own, but many of these reactions take place at a rate much too
slow to be of use to the cell.
6.
What would happen if enzymes were not present inside cells?
Many of the reactions of the cell would take place at a rate too slow to be of any use to the use. The cell
would likely die without the role played by the enzymes.
7.
Why is it essential that energy-releasing reactions take place inside living cells?
When a particular chemical reaction releases energy, this energy can then be used to power a reaction that
requires energy.
8.
What is activation energy?
Activation energy is the initial investment of energy needed for starting a reaction. It is the amount of
energy that must be absorbed by the reactants in order to break the bonds between the atoms composing
the reactant.
5
9.
How does an enzyme speed up a chemical reaction?
The enzyme lowers the amount of activation energy that is required to start the reaction. This makes the
reaction take place faster and at a lower temperature.
10.
Do all chemical reactions require activation energy? Explain.
Yes. An energy investment is always required to break the bonds of the reactant molecules. However, the
amount of activation energy is not the same for every reaction.
Fill in the Blank:
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
substrates
active site
product
chemical reaction
denature
lock and key
activation energy
a temperature and pH outside of the “normal” range for that enzyme
activation energy
enzyme-substrate complex
faster
temperatures
Most enzymes functions best at a temperature around 35 degrees Celsius.
Multiple Choice:
24.
25.
26.
b
c
c
True or False. Determine if the statement is true or false. If the statement is false, correct
the underlined word to make the statement true.
27.
Enzymes are biological hormones that help to speed up the chemical reactions of the cell.
False. The correct answer is “catalysts.”
28.
Chemical reactions involve changes in the chemical bonds that join atoms together in compounds.
True.
29.
Inside cells, chemical reactions require energy, but never release energy.
False. The correct answer is “and may also”.
30.
Starting a chemical reaction requires activation energy.
True
6
31.
Enzymes are very versatile and can be used in many different types of reactions.
False. Enzymes are very “specific” and can be used in “only one” type of reaction.
32.
The activation energy is usually in the form of heat that the reactant molecules absorb from their
surroundings.
True.
33.
Most enzymes function best at a pH range of 6 – 8.
True.
34.
Catalysts are affect by temperature and pH just as enzymes are.
False. The correct answer is “are not.”
35.
Neither enzymes nor catalysts are consumed in the reaction and may be used again.
True.
36.
If two reactants fail to react with one another, the addition of the enzyme will force them to react.
False. The correct answer is “will not.”
37. This diagram can be used to represent an enzymatic reaction. Label each part of the equation. Use the
equation to write a short description about how enzymes work.
Enzymes are proteins that have a unique three-dimensional shape. The active site is an area on the
enzyme that consists of a pocket, groove, or indentation. Each enzyme can “join” with only one
substrate that has a complimentary shape. If the substrate does not match the shape of the active
site on the enzyme, the enzyme does not speed up the reaction. If the enzyme active site and
substrate match, they bond together forming an enzyme-substrate complex. During this time, the
bonds of the reactant molecules are broken and new bonds are formed to produce new and
different products. At the end of the reaction, the enzyme remains unchanged and can be used over
and over again.
38. Explain what has happened if an enzyme has become “denatured.”
An enzyme that has become denatured has lost its unique, three-dimensional shape. Excessive heat
or chemicals may cause changes in the way the amino acids are bonded and folded in the enzyme. If
the enzyme has become denatured, the shape of the active site is no longer complimentary to the
shape of the substrate.
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39. Using the above diagram as a guide, draw a simple diagram showing what would happen if the
enzyme became denatured.
Most students will use the same equation drawing as seen above. However, the student should
change the shape of the enzyme so that it is apparent that the substrate can no longer fit into the
active site. The student should draw a misshapen enzyme plus a substrate, and indicate that the
reaction cannot proceed.
40. What might cause an enzyme to denature?
Enzymes are denatured when exposed to temperatures and pH levels that are outside of the normal
range for that particular enzyme.
Created by Amy Brown – Science Stuff
Copyright © January 2012 Amy Brown (aka Science Stuff)
All rights reserved by author.
This document is for your classroom use only.
This document may not be electronically distributed or posted to a web site.
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