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Enzymes Flashcards

1
Q

What are enzymes?

A

Biological catalysts that speed up chemical reactions in living organisms.

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2
Q

True or False: Enzymes are consumed in the reactions they catalyze.

A

False

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3
Q

What is the active site of an enzyme?

A

The region on the enzyme where substrate molecules bind and undergo a chemical reaction.

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4
Q

Fill in the blank: Enzymes are typically _____ in structure.

A

proteins

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5
Q

What is the role of substrates in enzymatic reactions?

A

Substrates are the reactants that enzymes act upon.

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6
Q

What is the Lock and Key model?

A

A model of enzyme action that suggests the enzyme’s active site is specifically shaped to fit a particular substrate.

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7
Q

What is the Induced Fit model?

A

A model of enzyme action that proposes the active site changes shape to better fit the substrate upon binding.

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8
Q

What factors can affect enzyme activity?

A

Temperature, pH, substrate concentration, and enzyme concentration.

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9
Q

True or False: Enzymes can function at a wide range of temperatures.

A

False

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10
Q

What is enzyme specificity?

A

The ability of an enzyme to select and catalyze only one or a few specific substrates.

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11
Q

What is a cofactor?

A

A non-protein molecule that assists enzymes in catalyzing reactions.

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12
Q

What are coenzymes?

A

Organic molecules that act as cofactors, often derived from vitamins.

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13
Q

Fill in the blank: The _____ is the measure of the rate at which an enzyme catalyzes a reaction.

A

enzyme activity

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14
Q

What is enzyme inhibition?

A

A process in which a molecule binds to an enzyme and decreases its activity.

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15
Q

True or False: Competitive inhibitors bind to the active site of the enzyme.

A

True

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16
Q

What is a non-competitive inhibitor?

A

An inhibitor that binds to an enzyme at a site other than the active site, reducing its activity regardless of substrate concentration.

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17
Q

What is allosteric regulation?

A

The regulation of an enzyme’s activity through the binding of molecules at sites other than the active site.

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18
Q

What is the effect of temperature on enzyme activity?

A

Enzyme activity typically increases with temperature up to an optimum point, after which it decreases.

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19
Q

Fill in the blank: The _____ is the pH level at which an enzyme is most active.

A

optimal pH

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20
Q

What is enzyme denaturation?

A

The process in which an enzyme loses its functional shape due to factors like extreme pH or temperature.

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21
Q

What is the Michaelis-Menten equation used for?

A

To describe the rate of enzymatic reactions with respect to substrate concentration.

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22
Q

What does Vmax represent in enzyme kinetics?

A

The maximum rate of reaction when the enzyme is saturated with substrate.

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23
Q

What is Km in enzyme kinetics?

A

The substrate concentration at which the reaction rate is half of Vmax.

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24
Q

What happens to enzyme activity at low substrate concentrations?

A

The reaction rate increases linearly with an increase in substrate concentration.

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25
Fill in the blank: Enzymes that catalyze the transfer of functional groups are called _____ enzymes.
transferase
26
What is a hydrolase?
An enzyme that catalyzes the hydrolysis of a chemical bond.
27
What type of enzyme catalyzes oxidation-reduction reactions?
Oxidoreductases
28
Fill in the blank: Enzymes that catalyze the formation of isomers are called _____ enzymes.
isomerase
29
What is the role of ligases?
Enzymes that catalyze the joining of two molecules using ATP.
30
What is enzyme regulation?
The process of controlling enzyme activity to meet cellular needs.
31
True or False: Enzymes can only catalyze one type of reaction.
False
32
What is the significance of enzyme kinetics?
It helps in understanding how enzymes work and how their activity can be controlled.
33
Fill in the blank: The study of enzyme function and structure is known as _____ biology.
enzymology
34
What is a zymogen?
An inactive precursor of an enzyme that requires a biochemical change to become active.
35
What is the role of feedback inhibition in metabolic pathways?
To regulate the production of metabolites and prevent overproduction.
36
What are enzyme assays used for?
To measure enzyme activity and concentration.
37
Fill in the blank: Enzymes can often be _____ to enhance their stability and activity.
modified
38
What is the role of enzymes in digestion?
To break down food into smaller molecules that can be absorbed by the body.
39
What is a biocatalyst?
A natural catalyst, such as an enzyme, that accelerates a biochemical reaction.
40
What is enzyme immobilization?
A technique used to confine enzymes to a specific location, enhancing their function and stability.
41
What is the significance of enzyme-substrate complex?
It is the temporary complex formed when an enzyme binds to its substrate.
42
Fill in the blank: Enzymes are crucial for _____ processes in living organisms.
metabolic
43
what is a rate-limiting step
In multi-step reactions the step with the highest activation energy is the rate-limiting step. To speed up the overall reaction the rate of this step must be increased. Some reactions may have multiple steps with similarly high activation energies – all these steps are rate limiting.
44
Is haemoglobin an enzyme?
no
45
What is the name of an enzyme made from RNA?
ribozyme
46
Which of the following is not a coenzyme? A) NADH B) Fe2+ C) Haem D) NAD+
B
47
ADH catalyses the reaction: Ethanol + NAD+ ➔ Acetaldehyde + NADH Which is the substrate? A) Ethanol B) NAD+ C) Acetaldehyde D) NADH
A
48
Which of the following describes a holoenzyme? A) An enzyme with no substrate bound B) An enzyme with no cofactor bound C) An enzyme with a substrate bound D) An enzyme with a cofactor bound
D
49
what is a Holoenzyme
A catalytically active enzyme, including all necessary subunits, prosthetic groups, and cofactors.
50
what is a apoenzyme
The protein portion of an enzyme, exclusive of any organic or inorganic cofactors or prosthetic groups that might be required for catalytic activity.
51
what is ground state
The energy level of “resting” substrates or products
52
what is the equation that links Keq (equilibrium constant) to ΔG
ΔG = −RT ln Keq
53
does breaking bonds release or use up energy
uses energy
54
does making bonds release or use up energy
releases energy
55
how do enzymes help entopy reduction
Enzymes restrict movement of substrates (so decrease disorder/entropy) making it more likely that they will collide and react.
56
how do enzymes help the removal of solvation shell during a reaction
Dissolved substances are surrounded by water molecules that may block reaction sites. A substrate binding to an enzyme usually loses its associated water molecules
57
what is a solvation shell
layers of water molecules (or other solvent molecules) that interact with the substrate through hydrogen bonding or dipole interactions. This shell stabilizes the substrate but can block interactions between the substrate and the enzyme's active site.
58
what is the Michaelis-Menten equation
V0 = Vmax [S] / Km + [S]
59
what is Michaelis constant Km
Km = [S] when V0 = 1/2 Vmax
60
what are the 6 things Vmax is dependant on
1. Specific substrate 2. Specific conditions 3. pH 4. Temperature 5. [Enzyme] 6. Inhibitors
61
what are the 2 things Km is dependant on
1. pH 2. Inhibitors
62
How are Vmax and Km affected by [enzyme]?
Vmax is proportional to [enzyme] Km is independent of [enzyme]
63
define Turnover number (kcat)
equivalent to the number of substrate molecules converted to product in a given unit of time on a single enzyme molecule when the enzyme is saturated with substrate Units: s-1
64
what is Sequential mechanism vs ping-pong mechanism
sequential mechamism: All substrates must bind to the enzyme before any product is released. ping-pong mechanism: One substrate binds, and one product is released before the second substrate binds.
65
why is Lineweaver-Burk plot used (3 reasons)
plots data on a straight line instead of a curve by using double reciprocals 1. Straight line makes it easier to analyze data compared to the curved Michaelis-Menten plot. 2. Allows calculation of Km and Vmax from the slope and intercepts 3. Useful for identifying enzyme inhibition types, because: Different types of inhibition affect the slope and intercepts in distinct ways
66
how does asprin work as a enzyme inhibitor
blocks synthesis of prostaglandins: molecules that cause pain.
67
how does cyanide work as a enzyme inhibitor
inhibits cytochrome c oxidase: this blocks cellular respiration.
68
what is mixed inhibition
Mixed inhibition occurs when an inhibitor binds both to the enzyme and the enzyme-substrate complex, leading to a decrease in Vmax​ and a variable effect on Km.
69
How do lines on a Lineweaver-Burk plot behave in mixed, competitive, uncompetitive, noncompetitive inhibition?
mixed inhibition: Lines intersect at a point that is not on either axis. Competitive inhibition: Lines intersect on the Y-axis. Uncompetitive inhibition: Lines are parallel. Noncompetitive inhibition (a special case of mixed): Lines intersect on the X-axis.
70
what is irreversible inhibitors
Irreversible inhibitors strongly bind to or destroy a functional group on an enzyme that is essential for the enzyme’s activity, inactivating the enzyme.
71
what are suicide inactivators
molecules that are unreactive until they bind the active site of an enzyme and are converted into irreversible inhibitors. This is important in drug design.
72

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