Lesson 1.7 - Enzymes

Question 1

Enzyme inhibitors _____ the rate at which an enzyme catalyzes a reaction.

Answer 1

Enzyme inhibitors lower the rate at which an enzyme catalyzes a reaction.

Question 2

_____ activity is affected by substrate and enzyme concentrations, temperature, and pH.

Answer 2

Enzyme activity is affected by substrate and enzyme concentrations, temperature, and pH.

Question 3

Describe how feedback inhibition reduces the waste of cellular resources.

Answer 3

The products of a reaction pathway inhibit the production of more products. Therefore, if there is too much product in the cell, the pathway is inhibited, and the resources needed for the intermediate steps in the pathway are not wasted.

Question 4

Define Allosteric Regulation

Answer 4

The regulation of one site of a protein by binding to another site on the same protein.

Question 5

Just prior to substrate binding, the enzyme changes its shape, or _____, so that the active site becomes even more precise in its ability to bind to its substrate (called _____ model).

Answer 5

Just prior to substrate binding, the enzyme changes its shape, or conformation, so that the active site becomes even more precise in its ability to bind to its substrate (called induced-fit model).

Question 6

What is a binding site on an enzyme that binds regulatory molecules known as?

Answer 6

Allosteric Site

Question 7

Enzymes bind to reactant(s), called substrates, and only interact with a very small region of the enzyme called _____.

Answer 7

Enzymes bind to reactant(s), called substrates, and only interact with a very small region of the enzyme called the active site.

Question 8

How does the rate of a reaction involving enzymes change as a result of the substrate concentration?

Answer 8

The rate of a reaction will increase with increasing substrate concentration until the enzyme reaches its saturation level. At this point there is no change in the rate of the reaction.

Question 9

Define Competitive Inhibition

Answer 9

A situation in which a competitor substance binds to a normal substrate binding site to block enzyme activity.

Question 10

How does the rate of a reaction involving enzymes change as a result of the pH?

Answer 10

Significant deviation from the optimal pH will cause enzyme denaturation.

Question 11

What is the functional role of a coenzyme or a cofactor in an enzyme-induced reaction?

Answer 11

Coenzymes and cofactors are required for an enzyme to properly catalyze a reaction.

Question 12

What group of macromolecules do almost all enzymes belong to?

Answer 12

Proteins

Question 13

_____ cofactors called coenzymes play similar roles. [They are] often derived from water-soluble vitamins.

Answer 13

Organic cofactors called coenzymes play similar roles. [They are] often derived from water-soluble vitamins.

Question 14

Humans produce enzymes in the mouth, stomach, and small intestine that aid in the process of digestions. As we age, we tend to produce less of these enzymes. What effect could this have on digestion and nutrition?

Answer 14

As we age, it becomes harder to utilize the nutrients in our food due to loss of function of digestive enzymes. This can lead to malnutrition and/or digestive problems.

Question 15

Describe noncompetitive enzyme inhibition.

Answer 15

A noncompetitive inhibitor binds to the enzyme at a site other than the active site. It changes the conformation of the enzyme so that it no longer binds its normal substrate.

Question 16

Why does an enzyme only help one particular reaction?

Answer 16

It only helps one because enzymes have particular shapes which are specific to their substrates.

Question 17

Enzymes usually reach maximal activity within a _____ range of temperatures and pH values (produces a peaked curve when enzyme activity is plotted).

Answer 17

Enzymes usually reach maximal activity within a narrow range of temperatures and pH values (produces a peaked curve when enzyme activity is plotted).

Question 18

The structure of penicillin mimics the structure of the two _____ acids that are normally brought together by the _____ site. Penicillin binds irreversibly to the active site of transpeptidase, effectively destroying the molecule.

Answer 18

The structure of penicillin mimics the structure of the two amino acids that are normally brought together by the active site. Penicillin binds irreversibly to the active site of transpeptidase, effectively destroying the molecule.

Question 19

What is the difference in a reaction with or without enzymes present?

Answer 19

Enzymes help to make the reaction move along faster.

Question 20

There are many industrial and commercial _____ of enzymes.

Answer 20

There are many industrial and commercial uses of enzymes.

Question 21

What happens to an enzyme that is heated or placed in acid?

Answer 21

It is denatured (3-D shape changes), and will no longer work.

Question 22

You are making a gelatin dessert, but the directions tell you not to use fresh pineapple because the gelatin will not solidify. Gelatin is a structural protein made from collagen. Pineapple contains an enzyme, bromelain, which is a protease.

Could you use cooked or canned pineapple instead? Explain your answer.

Answer 22

Yes, you can use cooked or canned pineapple in gelatin because the cooking or canning process denatures and inactivates the proteases in the pineapple.

Question 23

Explain how excess product can act as an allosteric inhibitor.

Answer 23

When there’s too much product, some will bind to the first enzyme and inhibit more product from being made, therefore the enzyme’s shape changes and doesn’t allow the substrate to bind.

Question 24

What is a situation in which molecules bind to an enzyme at a site that is not the active site, thus blocking enzyme activity known as?

Answer 24

Noncompetitive Inhibition

Question 25

Sometimes [inhibitors] bind so strongly through the formation of covalent bonds that they completely disable the enzyme, called _____.

Answer 25

Sometimes [inhibitors] bind so strongly through the formation of covalent bonds that they completely disable the enzyme, called irreversible inhibition.

Question 26

Each enzyme has a unique _____, which determines which reaction it catalyzes.

Answer 26

Each enzyme has a unique 3-D shape, which determines which reaction it catalyzes.

Question 27

Define Cofactor

Answer 27

A non-protein group that binds to an enzyme and is essential for catalytic activity.

Question 28

_____ inhibitors enter an enzyme’s active site to block the binding of the substrate. _____ inhibitors attach to another site on the enzyme, which changes the shape of the enzyme and its affinity for the substrate.

Answer 28

Competitive inhibitors enter an enzyme’s active site to block the binding of the substrate. Noncompetitive inhibitors attach to another site on the enzyme, which changes the shape of the enzyme and its affinity for the substrate.

Question 29

An active site is usually a pocket or groove that forms when the newly synthesized enzyme folds into its correct 3-D shape (_____ structure).

Answer 29

An active site is usually a pocket or groove that forms when the newly synthesized enzyme folds into its correct 3-D shape (tertiary structure).

Question 30

What is the regulation of a pathway by one of the products of this pathway known as?

Answer 30

Feedback Inhibition

Question 31

In terms of enzymes, why is it important for the human body to maintain a proper temperature and a proper pH at all times?

Answer 31

Maintenance of proper temperature and pH is important in providing optimal conditions for the body’s enzymes to perform their activity.

Question 32

Describe the induced-fit hypothesis of an enzyme substrate interaction.

Answer 32

In the induced-fit hypothesis, the conformation of the enzyme changes slightly to allow for a more precise binding of the substrate.

Question 33

Why is an enzyme considered a biological catalyst?

Answer 33

Enzymes are considered biological catalysts because they can be used repeatedly and are not wasted after they catalyze a reaction.

Question 34

Sometimes the binding of the inhibitor is weak and readily reversible (enzyme can return to normal function), called _____.

Answer 34

Sometimes the binding of the inhibitor is weak and readily reversible (enzyme can return to normal function), called reversible inhibition.

Question 35

What is the regulation of one site of a protein by binding to another site on the same protein known as?

Answer 35

Allosteric Regulation

Question 36

What is a non-protein group that binds to an enzyme and is essential for catalytic activity known as?

Answer 36

Cofactor

Question 37

Biochemical pathways often use _____ inhibition as a mechanism for regulating the pathway. In negative _____ inhibition, an enzyme involved at the beginning of the pathway is inhibited by a product in the pathway.

Answer 37

Biochemical pathways often use feedback inhibition as a mechanism for regulating the pathway. In negative feedback inhibition, an enzyme involved at the beginning of the pathway is inhibited by a product in the pathway.

Question 38

As temperature increases, the rate of a chemical reaction _____, due to increased kinetic motion of the molecules. As temperature rises, there are more frequent and stronger collisions.

Answer 38

As temperature increases, the rate of a chemical reaction increases, due to increased kinetic motion of the molecules. As temperature rises, there are more frequent and stronger collisions.

Question 39

A situation in which molecules bind to an enzyme at a site that is not the active site, thus blocking enzyme activity.

Answer 39

Noncompetitive Inhibition

Question 40

_____ regulation of enzymes can inhibit or stimulate enzyme activity by altering the _____ of the active site for the substrate.

Answer 40

Allosteric regulation of enzymes can inhibit or stimulate enzyme activity by altering the affinity of the active site for the substrate.

Question 41

Describe the different effects of an activator and an inhibitor on an allosterically regulated enzyme.

Answer 41

The activator binds in such a way that it stabilizes the active conformation of the enzyme, and it is then able to better bind the substrate. An inhibitor stabilizes the inactive conformation of the enzyme, so it cannot bind to its normal substrate.

Question 42

An enzyme is a biological _____ with a specific three-dimension shape, which is necessary for its function. The active site of an enzyme is specific to a particular substrate(s).

Answer 42

An enzyme is a biological catalyst with a specific three-dimension shape, which is necessary for its function. The active site of an enzyme is specific to a particular substrate(s).

Question 43

[Cofactors] are often _____, such as iron, copper, zinc, and manganese.

Answer 43

[Cofactors] are often metals, such as iron, copper, zinc, and manganese.

Question 44

Enzymes are of extreme medical interest because most of the drugs prescribed are _____.

Answer 44

Enzymes are of extreme medical interest because most of the drugs prescribed are inhibitiors.

Question 45

What is a biological catalyst, usually a protein, that speeds up a chemical reaction known as?

Answer 45

Enzyme

Question 46

What is a model of enzyme activity that describes how an enzyme changes shape to better accomodate a substrate known as?

Answer 46

Induced-Fit Model

Question 47

What is a substance that is recognized by and binds to an enzyme known as?

Answer 47

Substrate

Question 48

Define Allosteric Site

Answer 48

A binding site on an enzyme that binds regulatory molecules.

Question 49

What is a substrate and an active site? How are they related?

Answer 49

A substrate is a substance that is recognized and binds to an enzyme. An active site is the location on an enzyme where a substrate binds and is the location of the enzymatic reaction.

Question 50

What is a pocket or groove in an enzyme that binds its substrate known as?

Answer 50

Active Site

Question 51

Many enzymes require a _____, which is a non-protein group that binds very precisely to an enzyme.

Answer 51

Many enzymes require a cofactor, which is a non-protein group that binds very precisely to an enzyme.

Question 52

Define Enzyme

Answer 52

A biological catalyst, usually a protein, that speeds up a chemical reaction.

Question 53

We can also use the term _____ to describe an enzyme as well.

Answer 53

We can also use the term catalyst to describe an enzyme as well.

Question 54

All chemical reactions need a certain amount of energy in order to move forward or proceed (called _____, E_A). Enzymes _____ the amount of energy so it does not take as much energy for the reaction to occur and therefore the reaction goes faster.

Answer 54

All chemical reactions need a certain amount of energy in order to move forward or proceed (called activation energy, E_A). Enzymes decrease the amount of energy so it does not take as much energy for the reaction to occur and therefore the reaction goes faster.

Question 55

Define Active Site

Answer 55

A pocket or groove in an enzyme that binds its substrate.

Question 56

An enzyme usually speeds up a chemical reaction without being _____ or changing the products of the reaction.

Answer 56

An enzyme usually speeds up a chemical reaction without being consumed or changing the products of the reaction.

Question 57

Define Induced-Fit Model

Answer 57

A model of enzyme activity that describes how an enzyme changes shape to better accomodate a substrate.

Question 58

[The] binding of allosteric _____ molecule stabilizes the enzyme in a shape that causes its active site to have a high affinity for its substrate. In this high affinity state the enzyme binds its substrate.

Answer 58

[The] binding of allosteric activator molecule stabilizes the enzyme in a shape that causes its active site to have a high affinity for its substrate. In this high affinity state the enzyme binds its substrate.

Question 59

Digestion cannot take plcae unless water is present. Explain this statement.

Answer 59

Carbohydrates and proteins are broken down by hydrolysis into smaller subunits by the addition of water molecules. Without water, hydrolysis cannot happen, therefore, digestion cannot take place.

Question 60

Competitive inhibitors have shapes that resemble the normal substrate closely enough to fit into and occupt the _____ site.

Answer 60

Competitive inhibitors have shapes that resemble the normal substrate closely enough to fit into and occupt the active site.

Question 61

Molecules that naturally regulate enzyme activity in a cell often behave somewhat like a noncompetitive reversible inhibitor (called _____).

Answer 61

Molecules that naturally regulate enzyme activity in a cell often behave somewhat like a noncompetitive reversible inhibitor (called allosteric regulation).

Question 62

As the temperature rises, the kinetic motions of the amino acid chains of an enzyme _____. At the same time, the strength and frequency of the collisions between the enzyme molecules and any surrounding molecules also _____.

Answer 62

As the temperature rises, the kinetic motions of the amino acid chains of an enzyme increase. At the same time, the strength and frequency of the collisions between the enzyme molecules and any surrounding molecules also increases.

Question 63

How can one enzyme be used to repeatedly to form large molecules?

Answer 63

They can be recycled and used pepeatedly to make long polymers.

Question 64

You are making a gelatin dessert, but the directions tell you not to use fresh pineapple because the gelatin will not solidify. Gelatin is a structural protein made from collagen. Pineapple contains an enzyme, bromelain, which is a protease.

What effect does a protease have on a protein like collagen?

Answer 64

A protease is an enzyme that begins protein catabolism by breaking the peptide bonds that link the amino acids in the polypeptide chain. This disrupts the gelatin and stops it from setting.

Question 65

How would [competitive inhibition] slow the rate of reaction?

Answer 65

By binding to the active site, competitive inhibitors block access to the normal substrate and slow the rate of reaction.

Question 66

Define Feedback Inhibition

Answer 66

The regulation of a pathway by one of the products of this pathway.

Question 67

_____ inhibitors bind to enzymes at a location other than the active site, which changes the shape of the enzyme, reducing the ability of the substrate to bind efficiently.

Answer 67

Noncompetitive inhibitors bind to enzymes at a location other than the active site, which changes the shape of the enzyme, reducing the ability of the substrate to bind efficiently.

Question 68

How does the rate of a reaction involving enzymes change as a result of the temperature?

Answer 68

Temperature above the optimal point will slowly cause decrease of enzymatic activity and ultimately stop it at the point of denaturation; lower temperature will decrease the activity due to a decrease of available energy.

Question 69

[The] binding of an allosteric _____ stabilizes an inactive form of the enzyme. The inhibitor molecule changes the shape of the enzyme in such as way that the substrate is released from the active site.

Answer 69

[The] binding of an allosteric inhibitor stabilizes an inactive form of the enzyme. The inhibitor molecule changes the shape of the enzyme in such as way that the substrate is released from the active site.

Question 70

How does the rate of a reaction involving enzymes change as a result of the enzyme concentration?

Answer 70

As the concentration of enzyme increases, so does the rate of the reaction.

Question 71

What is a situation in which a competitor substance binds to a normal substrate binding site to block enzyme activity known as?

Answer 71

Competitive Inhibition

Question 72

_____ acts by inhibiting the synthesis of peptidoglycan, a key component of bacterial cell walls. [The] enzyme transpeptidase catalyzes the formation of a peptide bond between the two _____ acids that are responsible for linking two parts of peptidoglycan.

Answer 72

Penicillin acts by inhibiting the synthesis of peptidoglycan, a key component of bacterial cell walls. [The] enzyme transpeptidase catalyzes the formation of a peptide bond between the two amino acids that are responsible for linking two parts of peptidoglycan.

Question 73

Define Substrate

Answer 73

A substance that is recognized by and binds to an enzyme.