Chemistry - General, Organic, and Biological Chemistry:An Integrated Approach, Ch. 10

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1

Compounds that accelerate the reactions of metabolism but are not consumed or changed by those reactions.

Catalysts

2

Large, globular proteins found in every cell of the body. Act as catalysts.

Enzymes

3

In a chemical equation, where would the enzyme be shown?

Above or below the reaction arrow

4

Functional part of the enzyme where catalysis occurs.

Active site

5

An active site forms on the surface of an enzyme while it is folding into which structure? (primary, secondary, tertiary, or quaternary)

Tertiary structure

6

What is the reactant called in an enzyme-catalyzed reaction?

Substrate

7

The shape of an enzyme's active site is complementary to the shape of its substrate and no other substrate will fit into the site.

Substrate specificity

8

Name the two categories of nonprotein "helpers".

Cofactors and coenzymes

9

What is the difference between a cofactor and a coenzyme?

Cofactors are inorganic substances that can be obtained in a normal diet from minerals. Coenzymes are small, organic molecules, many of which are derived from vitamins.

10

True or False:
Intermolecular attractions (like Hydrogen bonding) help substrates find active sites of enzymes.

True

11

Initial interaction of an enzyme with a substrate forming proper orientation before catalysis begins.

Enzyme-substrate complex

12

True or False:
There are covalent bonds formed when the substrate and enzyme come into first contact.

False. There are NO covalent bonds formed when the substrate and enzyme come into first contact, only intermolecular attractions keep them together.

13

In which model is the active site a rigid, inflexible shape that is an exact complement to the shape of its substrate?

Lock and key model

14

In the lock and key model, how many substrates can each enzyme accommodate?

One

15

In which model is the active site flexible and has a shape that is roughly complementary to the shape of its substrate?

Induced fit model

16

In the induced fit model, how many substrates can react with an enzyme?

Two or more similar substrates

17

Reactions that release or produce energy as heat.

Exothermic

18

Reactions that absorb or consume energy as heat.

Endothermic

19

What two factors are required for a chemical reaction to occur?

1) Molecules must collide with each other with enough energy
2) Molecules must be in the proper orientation when they collide

20

Energy necessary to align the reactant molecules and to cause them to collide with enough energy to form products.

Activation energy

21

Energy difference between the products and the reactants.

Heat of reaction

22

Reactants are higher in energy than the products and energy is released into the surroundings as the reaction progresses.

Exothermic

23

Products are higher in energy than the reactants, indicating that energy is absorbed from the surroundings.

Endothermic

24

Will reactions with low activation energy proceed more quickly or slowly than reactions with high activation energy?

Quickly (have a faster rate)

25

How can we measure the rate of reaction?

By determining the amount of product formed or reactant used up in a certain period of time.

26

List three factors that affect rate of reaction.

Temperature, concentration of reactants, catalysts

27

How does a catalyst speed up a reaction?

By lowering the activation energy

28

What is the key to lowering the activation energy and allowing a biochemical reaction to proceed and quickly form products?

Enzyme-substrate complex

29

List three interactions that help lower the activation energy.

Proximity, orientation, bond energy

30

Is activation energy increased or decreased when the enzyme-substrate complex forms and the reacting molecules are in close proximity to each other?

Decreased

31

When an enzyme-substrate complex is formed, bonds of the substrate molecule(s) are weakened. Does this increase or decrease the activation energy?

Decrease

32

List four reaction conditions that affect enzyme-catalyzed reactions.

Substrate concentration, pH, temperature, inhibitors

33

The conditions under which the enzyme is operating at maximum activity.

Steady state

34

Once an enzyme has reached its steady state, increasing the concentration of substrate will:

A) increase the enzyme's activity
B) decrease the enzyme's activity
C) do nothing

C) do nothing

All of the enzyme contains substrate, leaving no more free active sites. Increasing the amount of substrate will not increase the activity further.

35

PH where enzymes are most active and maintain their tertiary structure and active site.

Optimum pH

36

When the pH of an enzyme's environment is changed, which structure is disrupted, altering the active site and causing the enzyme's activity to decrease? (primary, secondary, tertiary, or quaternary)

Tertiary structure

37

Above their optimum temperature, enzymes lose activity due to the disruption of the ____________ __________.

Intermolecular forces

38

True or False:
Denaturing of an enzyme at high temperatures modifies the structure of the active site.

True

39

What affect do low temperatures have on enzyme activity?

Enzyme activity is decreased due to the lack of energy present for the reaction to take place at all.

40

A molecule that prevents the active site from interacting with the substrate to form the enzyme-substrate complex.

Inhibitor

41

What is it called when and inhibitor is removed and the enzyme becomes functional again?

Reversible inhibition

42

Name two types of reversible inhibitors.

Competitive, noncompetitive

43

Molecules that compete with the substance for the active site.

Competitive inhibitors

44

Does a competitive inhibitor decrease or increase enzyme activity?

Decrease. As long as the competitive inhibitor remains in the active site, the enzyme cannot interact with its substrate and form product.

45

Inhibitors that do not resemble substrates and bind to a site other than the active site on the enzyme, causing the enzyme and its active site to change shape.

Noncompetitive inhibitors

46

How can inhibition by competitive inhibitors be reversed?

By adding more substrate to the reaction

47

How can inhibition by noncompetitive inhibitors be reversed?

By adding a special chemical reagent to remove the inhibitor and restore the catalytic activity of the enzyme

48

The inhibitor forms a covalent bond with an amino acid side chain in the enzyme's active site.

Irreversible inhibition