Chapter 12: Enzymes: The Protein Catalyst Flashcards

(55 cards)

1
Q

Define an enzyme.

A

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

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2
Q

What do enzymes allow?

A

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

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3
Q

What do enzymes facilitate?

A

Facilitates new product development

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4
Q

How many enzymes are in a cell?

A

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

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5
Q

Why do apples brown?

A
  • Oxidation

- Cell damage (+ important)

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6
Q

Define a catalyst.

A

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

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7
Q

What kind of substance are enzymes?

A

Group of proteins

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8
Q

How do we stop apples from browning?

A
  • Lemon juice (will denature enzymes)

- Salt (will denature enzymes)

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9
Q

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

A

Since enzymes do not change during chemical reactions

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10
Q

Define activation energy.

A

The energy needed to start a reaction

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11
Q

How do enzymes drive a reaction?

A

By lowering the amount of energy needed to start a reaction

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12
Q

What do digestive enzymes do?

A

Digestive enzymes decrease the amount of heat energy needed during digestion

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13
Q

Are enzymes specific?

A

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

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14
Q

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

A
  • 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
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15
Q

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

A

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

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16
Q

Name the 2 types of enzymatic models.

A

1) The lock and key model

2) The induced fit model

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17
Q

What does the induced-fit model address?

A

the limitations of the lock-and-key model

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18
Q

Define the induced-fit model.

A

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

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19
Q

Explain the basic process for enzymatic reactions.

A

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

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20
Q

Name 2 ways coenzymes work.

A

– 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

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21
Q

How do coenzymes work?

A

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

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22
Q

Name important coenzymes.

A
  • Vitamins and minerals

- the B vitamins, calcium, magnesium, and zinc

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23
Q

When was enzyme nomenclature accepted?

A

in 1961

Some enzymes had already been identified before the new naming system

24
Q

How are enzymes named?

A

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

25
The ____ name for the enzyme and the _____ are the same
root, substrate
26
What is the suffix for enzymes?
-ase
27
Name the 3 categories of digestive enzymes.
– Proteases break apart proteins – Lipases break apart lipids –Carbohydrases break apart starches and sugars
28
Do enzymes only have one name?
- Some enzymes have more than one name
29
Given an example of an enzyme that has more than one name.
Sucrase is also known as invertase because the mixture of glucose and fructose is often called invert sugar
30
Name 6 factors that affect enzyme activity.
1) Water availability 2) Concentration of the solution 3) Temperature 4) Acids and bases 5) Electrolytes 6) Enzyme inhibitor
31
How does water availability affect enzyme activity?
Water must be available to act as a reactant as well as a solvent in enzymatic reactions
32
What does the lack of water do to enzymatic activity?
Slows or stops it
33
Will enzymatic reactions occur in dry products?
no
34
Water must be a reactant in what reaction?
Breakdown of carbs, lipids and proteins
35
How does the concentration of the solution affect enzyme activity.
The more substrate in the solution, the greater | the rate of reaction is
36
The rate of the enzymatic reaction increases as concentration increases, up till where?
The saturation point
37
How does heat affect enzyme activity? Give an example.
- heat increases enzyme activity | - ex: blanching vegetables before freezing
38
How does pH affect enzyme activity?
A pH that is too high or too low will denature | an enzyme
39
How do electrolytes affect enzyme activity?
can prevent enzymes from reacting with a | substrate
40
How do enzyme inhibitors affect enzyme activity?
prevents enzyme-substrate complexes from forming
41
How do enzyme inhibitors act?
change the shape of the enzyme or the | substrate
42
How do enzyme inhibitors protect foods?
Protect from bacteria and mold by stopping the digestive enzymes they release from working
43
Where do enzyme inhibitors occur?
They occur naturally in a wide variety of foods from animal and plant sources
44
Name 3 ways enzymes are used by the food industry to develop new products.
– 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
45
Name 4 positive effects of enzymes in the food supply.
– make food easier to eat – preserve food – improve flavor, quality, or appearance – plays a role in fermentation
46
Name 3 negative effects of enzymes in the food supply.
– break down the structure of fruits and vegetables – unpleasant flavor and odor changes – undesirable changes in texture and color
47
How are carbohydrases used commercially?
react with sugars and starches for commercial uses.
48
Name 4 products of carbohydrases in food production.
– make corn syrup and high-fructose corn syrup | – ferment wine and beers – stabilize chocolate syrup – clarify fruit juices
49
Name 2 ways lipases are used in food production.
– 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
50
Name 5 ways proteases are used in food production.
– 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
51
What do oxidases do?
Deteriorate ripe fruits and vegetables when stored in an oxygen environment (must be stored in oxygen-free)
52
In what products would enzymatic browning be desirable? In what products would they be undesirable?
- Desirable: raisins, figs | Undesirable: sliced apples or pears
53
How does the food industry prevent browning of cut fruit?
Uses acids as enzyme inhibitors
54
How can the primary structure of proteins be destroyed?
Proteases
55
Why does sodium hydroxide make an apple brown?
It is oxidizing (there is oxygen)