Chapter 12: Enzymes: The Protein Catalyst

Question 1

Define an enzyme.

Answer 1

Specialized protein that speeds up or starts a chemical reaction without being changed by the reaction

Question 2

What do enzymes allow?

Answer 2

Allows chemical reactions in the cells to happen fast enough to meet the body’s needs

Question 3

What do enzymes facilitate?

Answer 3

Facilitates new product development

Question 4

How many enzymes are in a cell?

Answer 4

Thousands of enzymes are in a cell, each having a unique function

Question 5

Why do apples brown?

Answer 5

• Oxidation

- Cell damage (+ important)

Question 6

Define a catalyst.

Answer 6

A catalyst is a substance that speeds up a reaction between substances without being affected by the reaction

Question 7

What kind of substance are enzymes?

Answer 7

Group of proteins

Question 8

How do we stop apples from browning?

Answer 8

• Lemon juice (will denature enzymes)

- Salt (will denature enzymes)

Question 9

Why do cells only need a low concentration of many different enzymes?

Answer 9

Since enzymes do not change during chemical reactions

Question 10

Define activation energy.

Answer 10

The energy needed to start a reaction

Question 11

How do enzymes drive a reaction?

Answer 11

By lowering the amount of energy needed to start a reaction

Question 12

What do digestive enzymes do?

Answer 12

Digestive enzymes decrease the amount of heat energy needed during digestion

Question 13

Are enzymes specific?

Answer 13

Yes, enzymes are specific to the compounds with which they will react

Question 14

Define the key and keyhole in the lock and key model.

Answer 14

• The key represents the substance being changed, known as the substrate
• The keyhole, or active site, is where the substrate attaches to the enzyme.
• The key must be inserted in the RIGHT spot in the right way

Question 15

Why is the lock and key model limited? What does research indicate?

Answer 15

That the substrate does not turn when inserted into the active site and an enzyme is not a perfect match to the substrate

Question 16

Name the 2 types of enzymatic models.

Answer 16

1) The lock and key model

2) The induced fit model

Question 17

What does the induced-fit model address?

Answer 17

the limitations of the lock-and-key model

Question 18

Define the induced-fit model.

Answer 18

The active site temporarily changes the shape of the enzyme to allow the reaction to occur, then returns to its original configuration after the reaction

Question 19

Explain the basic process for enzymatic reactions.

Answer 19

1) Enzyme and substrate combine to form an enzyme-substrate complex
2) Enzyme-substrate complex is unstable and breaks apart, leaving the enzyme to act again on another substrate

Question 20

Name 2 ways coenzymes work.

Answer 20

– attaching to the enzyme and changing its shape so the substrate can fit in the active site
– attaching to the substrate and changing its shape so it will fit the active site of the enzyme

Question 21

How do coenzymes work?

Answer 21

acting as a transfer agent by accepting an atom or molecular group and transferring it to another compound

Question 22

Name important coenzymes.

Answer 22

• Vitamins and minerals

- the B vitamins, calcium, magnesium, and zinc

Question 23

When was enzyme nomenclature accepted?

Answer 23

in 1961

Some enzymes had already been identified before the new naming system

Question 24

How are enzymes named?

Answer 24

enzymes are named for the types of reactions or substances for which they are the catalyst

Question 25

The ____ name for the enzyme and the _____ are the same

Answer 25

root, substrate

Question 26

What is the suffix for enzymes?

Answer 26

-ase

Question 27

Name the 3 categories of digestive enzymes.

Answer 27

– Proteases break apart proteins
– Lipases break apart lipids
–Carbohydrases break apart starches and sugars

Question 28

Do enzymes only have one name?

Answer 28

• Some enzymes have more than one name

Question 29

Given an example of an enzyme that has more than one name.

Answer 29

Sucrase is also known as invertase because the mixture of glucose and fructose is often called invert sugar

Question 30

Name 6 factors that affect enzyme activity.

Answer 30

1) Water availability
2) Concentration of the solution
3) Temperature
4) Acids and bases
5) Electrolytes
6) Enzyme inhibitor

Question 31

How does water availability affect enzyme activity?

Answer 31

Water must be available to act as a reactant as well as a solvent in enzymatic reactions

Question 32

What does the lack of water do to enzymatic activity?

Answer 32

Slows or stops it

Question 33

Will enzymatic reactions occur in dry products?

Answer 33

no

Question 34

Water must be a reactant in what reaction?

Answer 34

Breakdown of carbs, lipids and proteins

Question 35

How does the concentration of the solution affect enzyme activity.

Answer 35

The more substrate in the solution, the greater

the rate of reaction is

Question 36

The rate of the enzymatic reaction increases as concentration increases, up till where?

Answer 36

The saturation point

Question 37

How does heat affect enzyme activity? Give an example.

Answer 37

• heat increases enzyme activity

- ex: blanching vegetables before freezing

Question 38

How does pH affect enzyme activity?

Answer 38

A pH that is too high or too low will denature

an enzyme

Question 39

How do electrolytes affect enzyme activity?

Answer 39

can prevent enzymes from reacting with a

substrate

Question 40

How do enzyme inhibitors affect enzyme activity?

Answer 40

prevents enzyme-substrate complexes from forming

Question 41

How do enzyme inhibitors act?

Answer 41

change the shape of the enzyme or the

substrate

Question 42

How do enzyme inhibitors protect foods?

Answer 42

Protect from bacteria and mold by stopping the digestive enzymes they release from working

Question 43

Where do enzyme inhibitors occur?

Answer 43

They occur naturally in a wide variety of foods from animal and plant sources

Question 44

Name 3 ways enzymes are used by the food industry to develop new products.

Answer 44

– converting one food product into another, such as with milk into cheese
– extracting food components from food systems such as the separation of juice from insoluble residues
– playing a key role in developing ingredients

Question 45

Name 4 positive effects of enzymes in the food supply.

Answer 45

– make food easier to eat
– preserve food
– improve flavor, quality, or appearance
– plays a role in fermentation

Question 46

Name 3 negative effects of enzymes in the food supply.

Answer 46

– break down the structure of fruits and vegetables
– unpleasant flavor and odor changes
– undesirable changes in texture and color

Question 47

How are carbohydrases used commercially?

Answer 47

react with sugars and starches for commercial uses.

Question 48

Name 4 products of carbohydrases in food production.

Answer 48

– make corn syrup and high-fructose corn syrup

– ferment wine and beers – stabilize chocolate syrup – clarify fruit juices

Question 49

Name 2 ways lipases are used in food production.

Answer 49

– extract unwanted egg yolk from egg white to
improve the whipping properties of egg white
– improve flavor and texture of various products including cheese, ice cream, margarine, butter, and many baked goods

Question 50

Name 5 ways proteases are used in food production.

Answer 50

– tenderize meat by breaking long protein fibers,
as in solutions for marinated meat
– reduce the size of proteins extracted from malt
and grains during beer and ale production – reduce mixing time
– increase pliability of dough
– change food into a different product, such as milk into cheese

Question 51

What do oxidases do?

Answer 51

Deteriorate ripe fruits and vegetables when stored in an oxygen environment (must be stored in oxygen-free)

Question 52

In what products would enzymatic browning be desirable? In what products would they be undesirable?

Answer 52

• Desirable: raisins, figs

Undesirable: sliced apples or pears

Question 53

How does the food industry prevent browning of cut fruit?

Answer 53

Uses acids as enzyme inhibitors

Question 54

How can the primary structure of proteins be destroyed?

Answer 54

Proteases

Question 55

Why does sodium hydroxide make an apple brown?

Answer 55

It is oxidizing (there is oxygen)