Chapter 20

Question 1

Enzymes are biological catalysts that:
- Increase the rate of reaction by altering the way a reaction takes place.
- Are not changed in the process of said reaction.
And…

Answer 1

• Lower the activation energy of the reaction.

Question 2

Enzymes increase the rate of a chemical reaction by ___ ____ ___ required to convert reactant molecules to products.

Answer 2

reducing the energy

Question 3

Nearly all enzymes are…
1) are ___ ___ with a unique three-dimensional shape that recognizes+binds a small group of reacting molecules, called 2) ____.

Answer 3

1) Globular proteins, 2) substrates

Question 4

Nearly all enzymes have a 1) ___ ___ that includes a region called the active site where one or more small groups of 2) ___ 3) ____ to create a chemical reaction.

Answer 4

1) tertiary structure, 2) substrates, 3) bind

Question 5

Nearly all enzymes have specific amino acid residues within the active site that interact with functional groups of the substrate to form: 1) ___ ___, 2) ___ ___, and 3) ____ ____.

Answer 5

1) hydrogen bonds, 2) salt bridges, 3) hydrophobic interactions

Question 6

Types of Substrate Specificity:

Absolute: Reaction type

Answer 6

Catalyzes one type of reaction for one substrate.

Ex: Urease catalyzes only the hydrolysis of urea.

Question 7

Types of Substrate Specificity:
Group: reaction type

Answer 7

Catalyzes one type of reaction for similar substrates.

ex: Hexokinase adds a phosphate GROUP to hexoses.

Question 8

Types of Substrate Specificity:
Linkage: Reaction type

Answer 8

Catalyzes one type of reaction for a specific TYPE of bond.

Ex: Chymotrypsin catalyzes the hydrolysis of peptide bonds.

Question 9

The combination of an enzyme and a substrate forms an _____.

Answer 9

eznyme-substrate (ES) complex.

What does it do? Provides alternative pathway for reaction with lower activation energy.

Question 10

Lock and key model: Has a 1) ___ substrate binding to a 1) ___ enzyme. Much like a key fitting into a lock.

Answer 10

1) Rigid

Question 11

Induced-fit model: more 1) model of enzyme action. States that the active site is 2) ___ enough to adapt to the shape of the substrate.

Answer 11

1) dynamic, 2) flexible

Question 12

With the induced-fit model, the substrate and the enzyme work together to do what?

Answer 12

Lower the activation energy.

Question 13

What is the active site?
a) the entire enzyme
b) section of the enzyme
c) substrate

Answer 13

b) section of the enzyme

Question 14

In the induced-fit model, what happens to the shape of the enzyme when the substrate binds?
A) Stays the same
B) adapts to the shape of the substrate

Answer 14

b) adapts to the shape of the substrate

Question 15

What is the suffix for an enzyme?

Answer 15

Usually -ase
Example: sucrase catalyzes the reaction of sucrose.

Question 16

What are the common names for some digestive enzymes?

Answer 16

Pepsin, trypsin.

Question 17

Classification of enzymes
Oxidoreductases: What do they do?

Answer 17

They catalyze oxidation-reduction reactions.

Question 18

Classification of enzymes:
Transferases: What do they do?

Answer 18

They catalyze the transfer of a functional group between two compounds.

Question 19

Classification of enzymes:
Hydrolases: What do they do?

Answer 19

They catalyze hydrolosis (Add H2O) reactions that split a compound into two parts.

Question 20

Classification of enzymes:
Lyases: What do they do?

Answer 20

They catalyze the addition or removal of a group without hydrolosis.

Question 21

Classification of enzymes:
Isomerases: What do they do?

Answer 21

They catalyze the rearrangement (isomerization) of atoms within a substrate.

Question 22

Classification of enzymes:
Lygases: What do they do?

Answer 22

They catalyze the joining of two substrates, using ATP energy.

Question 23

Match the type of reaction with an enzyme:
1) aminase
2) dehyrdrogenase
3) isomerase
4) synthetase

a) converts a cis fatty acid to ta trans fatty acid
b) removes two H atoms to form a double bond
c) combines two molecules to make a new compound
d) Adds NH3

Answer 23

3A
2B
4C
1D

Question 24

Enzymes are most active at an ____ _____.

Answer 24

Optimum temperature.

Question 25

Enzymes 1) _____ at 2) _____ temperatures.

Answer 25

1) Denature, 2) high

Question 26

Thermophiles live in 1) ____ temperatures, ranging from 2) ___ to ___ degrees celcius.

Answer 26

1) high, 2) 50 to 120

Question 27

What structure do thermophiles have that prevent them from being destroyed from such high temperatures?

Answer 27

Tertiary Structures.

Question 28

Enzyme concrentration:
An increase in enzyme concentration increases the 1) _____.
This is because it binds more 2) ____ with 3) ____.

Answer 28

1) rate of reaction, 2) substrate, 3) enzyme

Question 29

An increase in 1) ____ concentration increases the 2) ______ and eventually 3) _____ to give maximum activity.

Answer 29

1) substrate, 2) rate of reaction, 3) saturates (with an enzyme)

Question 30

If sucrose has an optimum temperature of 37 degrees celcius and an optimum pH of 6.2, determine the effect of the following steps on its rate of reaction:
A) INCREASING THE CONCENTRATION OF SUCRASE
B) CHANGING pH to 4.0
C) RUNNING THE REACTION AT 70 DEGREES CELCIUS

1. No change
2. Increase
3. Decrease

Answer 30

A. 2 - We are increasing the concentration of enzyme, so it will increase.
B. 3 - We are taking the sucrase away from its optimum pH, which will affect its rate of reaction negatively (decrease)
C. 3 - We are taking the sucrase away from its optimum temperature, which will decrease its rate of reaction.

Question 31

Regulation of Enzyme Activity
Phosphorylation is a type of covalent modification that 1) ____ OR _____ and enzyme.

Answer 31

1) activates or deactivates an enzyme.

Question 32

Enzyme regulation
The rates of enzyme-catalyzed reactions are controlled by regulatory enzymes that:
1) ____ the 2) _____ when more of a particular substance is needed.
And subsequently… vice versa.

Answer 32

1) increase the 2) reaction rate

Question 33

Allosteric Enzymes:
They 1) ____ with a regulator molecule at the 2) ____ site that is different from the active site.

Answer 33

1) bind, 2) allosteric

Question 34

Allosteric Enzymes:
1) ____ the shape of the enzyme, which causes a change in the shape of the active site.

Answer 34

1) change

Question 35

Allosteric Enzymes:
Positive regulators: they 1) ____ the shape of the active site to allow the substrate to 2) ____ more effectively.

Answer 35

1) change, 2) bind

Question 36

Allosteric Enzymes:
The vice versa of a positive regulator, the negative regulator changes the shape of the active site to 1) ____ the proper binding of the substrate, which 2) ____ the rate of the catalyzed reaction.

Answer 36

1) inhibit/prevent 2) decreases

Question 37

Feedback control:
When the end product’s level is high,
The end product of a series acts as a 1) _____ and binds to the 2) _____.

Answer 37

1) negative regulator (as it comes to the end of its reaction, 2) allosteric site.

Question 38

Feedback control:
When the end product’s level is high, the substrate cannot 1) _____ to the ____. The production of all 3) _____ _____ in the subsequent reaction sequence stops.

Answer 38

1) bind, 2) active site, 3) intermediate compounds

Question 39

Covalent modification; what exactly is it?

Answer 39

Covalent modification is another way in which enzymes are modified.
Enzyme activity is modified by covalent bonds to a group on the 🌟 polypeptide chain that are formed or broken.

Question 40

TRUE OR FALSE:
Covalent modification is reversible?

Answer 40

TRUE!

Question 41

Covalent Modification:
Zymogens are also called 1) ____.
They are produced in their 2) ____ and can be activated at a 3) ____ when 4) ______.

Answer 41

1) 🌟 proenzymes, 2) inactive form, 3) later time, 4) when they are needed

Question 42

Zymogens include:

Answer 42

Digestive enzymes,
protein hormones (insulin),
blood clotting enzymes,
proteases,
digestive enzymes that hydrolize protein (produced as larger & inactive forms)

Question 43

Zymogens/Proenzymes:
Once a zymogen is formed, it is:
1) _____ to where the active form is needed
2) _____ to its active form by a _____.

Answer 43

1) transported, 2) converted to its active form by a covalent modification

Question 44

Where are zymogens such as proteases typsinogen and chymotrypsinogen stored?

Answer 44

They are stored in the Pancreas until after food is ingested. They are released when triggered by hormones BY the pancreas.

Question 45

An inactive enzyme undergoes covalent modification in which an enzyme….
A) can be ACTIVATED by the ADDITION of a phosphate group…
And subsequently, B) can be _____ by the ______ of a phosphate group.

Answer 45

B) Can be DEACTIVATED by the REMOVAL of a phosphate group.

Question 46

Indicate whether A, B, AND C are describing enzyme regulation by: 1) allosteric enzyme, 2) zymogen, or 3) covalent modification.
A) An end product attaches to the regulatory site of the first enzyme in the reaction sequence.
B) Proinsulin forms in the pancreas.
C) Phosphorylase kinase deactivates pyruvate dehydrogenase.

Answer 46

A) 1 - This is an allosteric enzyme occurring from the end of the reaction, which attaches to the active/regulatory site in order to allow reactions or inhibit reactions (likely inhibit, as it is an end product).
B) 2- Zymogens are released from the 🌟 panceas via hormones in order to assist in processing food (insulin is also an important factor in determining this).
C) 3 - This is because we are discussing activation and deactivation, which has to do highly with covalent modification.

Question 47

Isoenzymes are different forms of an enzyme that catalyze the same reaction in different cells or tissues of the body.
What structures do they have, and what kind of variations do they have?

Answer 47

Isoenzymes have QUATERNARY structures with slight variations in the AMINO ACIDS in the polypeptide subunits.

Question 48

Myocardiaol infarction (I did not mispell that) may be indicated by an increase in the levels of: 1)____, and 2) _____

Answer 48

1) Creatije Kinase (CK) and 2) Lactate Dehydrogenase (LDH)

Question 49

Myocardial infarction may be indicated by Creatije Kinase (CK) and 2) Lactate Dehydrogenase (LDH).

What is special about these to allow medical diagnosis of damage or disease or the particular organ or tissue?

Answer 49

The different ORMS of an enzyme allow for key medical diagnosis.

Question 50

INHIBITORS: What are they, and what are their roles?

Answer 50

Inhibitors are molecules that cause a LOSS of catalytic activity.
🌟 They prevent substrates from fitting into active sites.
🌟 They can be: REVERSIBLE or IRREVERSIBLE.

Question 51

Reversible inhibition:
Cause a loss of enzyme activity that can be 1) ____. Can act in different ways but do NOT form 2) _____ with the enzyme.

Answer 51

1) restored, 2) covalent bonds

Question 52

Reversible Inhibition can be competitive or non competitive: what is the difference?

Answer 52

COMPETITIVE inhibitors… compete for the active site.
NONCOMPETITIVE inhibitors act on another site that is NOT the active site. (They’re so cute <3)

Question 53

What is the structure of a COMPETITIVE inhibitor?

Answer 53

They have chemical structures and polarity SIMILAR to the substrate.
They compete with the substrate for the active site.
You can reverse its effect by INCREASING substrate concentration (send the opps).

Question 54

Antimetabolites: Competitive inhibitors involved with medicine.
Because of their competitive nature, some 1) ______ are treated with competitive inhibitors called 2) ______.

Answer 54

1) bacterial infections, 2) antimetabolites.
This is because the antimetabolites are the bacteria’s opps. This is because antimetabolites compete with p-aminobenzoic acid (PABA), which is an essential metabolite in a bacteria growth cycles.

Question 55

Noncompetitive inhibitors:
Have structures that vary highly from the substrate’s. They do not compete for the active site.
They 1) ____ the shape of the enzyme, which 2) _____ the susbtrate at the active site.
🌟 They cannot have its 3) _____ by adding more substrate.

Answer 55

1) distort, 2) prevents the binding of the substrate, and 3) cannot have its effect reversed by adding more substrate.

Question 56

In reversible inhibition, enzyme activity is destroyed when…
- the inhibitor 1) _____ bonds with R groups of an 2) ____ that may be near the active site.

Answer 56

1 covalently bonds 2) amino acids

Question 57

In reversible inhibition, enzyme activity is destroyed when…
- the inhibitor 1) ____ the shape of the enzyme, which prevents the substrate from entering the active site.

Answer 57

The inhibitor changes the shape of the enzyme.