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biochemistry-introduction > ENZYMES > Flashcards

ENZYMES Flashcards

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1
Q

What are enzymes?

A

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

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2
Q

What are the two main types of metabolism?

A

Catabolism (breakdown, energy-releasing) and Anabolism (synthesis, energy-requiring).

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3
Q

What are catabolic reactions?

A

Energy-yielding reactions involved in the breakdown of complex molecules into simpler ones.

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4
Q

What are anabolic reactions?

A

Energy-requiring reactions involved in building up simpler molecules into more complex ones.

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5
Q

What is a metabolic pathway?

A

A series of steps, beginning with a specific molecule and ending with a product

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6
Q

What is activation energy?

A

The energy barrier that must be overcome for a substrate to become a product.

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7
Q

What does the graph illustrate about activation energy (Ea) in a chemical reaction?

A

It is the energy barrier that must be overcome for reactants to transition to products.

It is represented by the peak of the curve. The higher the peak, the greater the activation energy required.

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8
Q

What is the primary effect of an enzyme on the activation energy of a chemical reaction?

A

Enzymes lower the activation energy of a chemical reaction.

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9
Q

How do enzymes speed up reactions?

A

By lowering activation energy and stabilizing the transition state.

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10
Q

How do enzymes affect activation energy?

A

Enzymes lower the activation energy required for a reaction to proceed.

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11
Q

How does temperature affect reaction rates?

A

Heat is an inefficient means of speeding up reactions since it simply is a means of increasing the random jostling of molecules.

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12
Q

What are the six classes of enzymes? Over The HILL

A

Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, and Ligases.

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13
Q

What do oxidoreductases catalyze?

A

Oxidation-reduction reactions.

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14
Q

What do transferases do?

A

Transfer functional groups from one molecule to another.

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15
Q

What do hydrolases catalyze?

A

Hydrolytic cleavage.

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16
Q

What do lyases catalyze?

A

Removal of a group from or addition of a group to a double bond, or other cleavages involving electron rearrangement.

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17
Q

What do isomerases catalyze?

A

Intramolecular rearrangement.

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18
Q

What do ligases catalyze?

A

Reactions in which two molecules are joined.

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19
Q

What are cofactors and coenzymes?

A

Non-protein molecules that help enzymes function.

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20
Q

Give examples of cofactors.

A

Inorganic molecules like Mg2+, Zn2+, Mn2+.(Metal ions)

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21
Q

Give examples of coenzymes.

A

Small organic molecules, often derivatives of vitamins (e.g., thiamin, riboflavin, niacin, biotin).

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22
Q

What is a holoenzyme?

A

Enzyme + Co-enzyme.

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23
Q

What is an apoenzyme?

A

Enzyme alone.

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24
Q

What are the two models of enzyme-substrate binding?

A

Lock & Key Model and Induced Fit Model.

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25
What happens when substrates enter the active site of an enzyme?
The enzyme changes shape to embrace the substrates, following the induced fit model.
26
How are substrates held in the active site?
Substrates are held in the active site by weak interactions such as hydrogen bonds and ionic bonds.
27
What is the function of the active site and the R groups of amino acids in catalysis?
They lower activation energy (Ea) by: Acting as a template for substrate orientation. Stressing and stabilizing the transition state. Providing a favorable microenvironment. Participating directly in the reaction.
28
What happens to substrates during enzyme-mediated catalysis?
Substrates are converted into products through enzymatic reaction.
29
What happens after products are released from the enzyme?
The enzyme's active site becomes available for new substrate molecules, allowing the reaction cycle to continue.
30
Describe the Lock and Key theory.
It implies that the binding site for a substrate on the enzyme is a rigid
31
Describe the Induced Fit theory.
It assumes that the enzyme is flexible, and after substrates bind, the conformation of the protein changes so that a stable binary complex form
32
List four mechanisms of catalysis.
Active sites are able to: Orient substrate in proper orientation so as new bonds are formed Stretch the substrate so as bonds are broken maintain conducive physical environment participate directly in the rxn
33
What is the active site?
The site of catalysis on an enzyme.
34
What is the role of the rest of the enzyme?
Supporting the active site Controlling reaction rates Attaching to other things
35
Besides binding to the substrate(s), what else does induced fit allow the enzyme to do?
Provides a subtle application of energy (e.g., "bending" chemical bonds) that causes the substrate(s) to destabilize into the transition state.
36
What does induced fit serve to do?
Bring specific functional groups on the enzyme into the proper position to catalyze the reaction.
37
What does the conformational change in induced fit permit?
Formation of additional weak bonding interactions in the transition state.
38
What do properly positioned catalytic functional groups do once a substrate is bound to an enzyme?
Aid in the cleavage and formation of bonds by a variety of mechanisms, including general acid-base catalysis, covalent catalysis, and metal ion catalysis
39
What is enzyme saturation, and how does it affect reaction rate?
Enzyme saturation occurs when all active sites of an enzyme are occupied by substrate molecules. Once saturation is reached, increasing substrate concentration does not increase the reaction rate further because no more active sites are available.
40
What is non-specific inhibition of enzyme activity?
It refers to factors that affect enzyme activity broadly, such as temperature and pH, rather than specific inhibitors binding to the enzyme.
41
What are some factors that influence enzyme activity?
Temperature, pH, enzyme stability, and changes in the enzyme’s structure.
42
How does temperature affect enzyme activity?
Low temperatures reduce enzyme fluidity and reaction rates, while high temperatures cause denaturation and loss of function.
43
What happens to an enzyme when it is denatured?
Its shape is altered, preventing it from binding to substrates properly, which stops its catalytic activity.
44
Why does enzyme activity decrease at low temperatures?
Enzymes become less fluid, reducing their ability to interact with substrates effectively.
45
How does pH influence enzyme activity?
It affects the ionization of R groups, which can change the enzyme's shape and function.
46
What happens to enzyme activity at an extreme pH?
The enzyme may lose its shape, reducing or stopping its ability to catalyze reactions.
47
What is the optimal pH for most enzymes?
It varies, but typically around neutral for human enzymes, while some (e.g., pepsin) function best in acidic conditions.
48
What is meant by "turnover rate" in enzymology?
It refers to the number of substrate molecules converted to product per enzyme molecule per second.
49
What is an inhibitor?
A substance that binds to an enzyme and interferes with its activity.
50
What are the two ways an inhibitor can interfere with enzyme activity?
1. Prevent formation of the ES complex. 2. Prevent ES breakdown to E + P.
51
What are the two classes of inhibitors?
Irreversible and Reversible Inhibitors.
52
How do irreversible inhibitors bind to enzymes?
Through covalent bonds (binds irreversibly).
53
How do reversible inhibitors bind to enzymes?
Through non-covalent interactions (disassociates from enzyme).
54
How do competitive inhibitors work?
They bind to the active site of the enzyme, preventing the substrate from binding.
55
How can the effects of competitive inhibition be reversed?
By increasing the substrate concentration.
56
How do non-competitive inhibitors work?
They bind to a different site on the enzyme (not the active site), changing the enzyme's shape so the substrate cannot bind.
57
Can non-competitive inhibition be reversed by increasing substrate concentration?
No, because the enzyme’s shape is altered, preventing substrate binding.
58
What happens to the rate of reaction when an inhibitor is present?
It decreases or stops depending on the type of inhibitor.
59
What type of inhibition is more likely to completely stop enzyme activity?
Non-competitive inhibition, since it changes the enzyme’s shape permanently.
60
What does a substrate need to do to bind to an enzyme?
It must have a complementary shape to the active site.
61
Why does increasing substrate concentration help in competitive inhibition?
Because more substrate molecules can outcompete the inhibitor for the active site.
62
What is an allosteric activator?
A molecule that binds to an allosteric site and stabilizes the enzyme in its active form, increasing catalysis.
63
How does an allosteric inhibitor affect enzyme activity?
It binds to an allosteric site, stabilizing the enzyme in its inactive form and decreasing catalysis.
64
What determines the effect of an allosteric interaction?
The binding constant and density of the effector.
65
How do allosteric activators and inhibitors regulate enzyme function?
They control the rate of an enzyme-catalyzed reaction by stabilizing either the active or inactive form.
66
What is cooperativity in enzyme function?
It is when the binding of a substrate to one subunit increases the activity of other subunits.
67
How does substrate binding affect an enzyme exhibiting cooperativity?
It locks all subunits in an active conformation, enhancing the enzyme’s activity.
68
How is cooperativity different from typical allosteric activation?
In cooperativity, the substrate itself acts as the activator by stabilizing the enzyme's active form.
69
What happens to an enzyme in its inactive form during cooperativity?
Binding of one substrate molecule helps shift the enzyme from an inactive to a stabilized active form.
70

biochemistry-introduction (4 decks)

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