ENZYME OVERVIEW Flashcards

Question

What are **enzymes**?

Answer 1

Biological catalysts that accelerate chemical reactions ## Footnote Enzymes are highly specific and can be reused in reactions.

Answer 2

* Acid/Base Catalysis * Covalent Catalysis * Electrostatic Catalysis ## Footnote Each method employs different mechanisms to lower activation energy.

Answer 3

Involves donation or acceptance of protons to facilitate reactions ## Footnote Acid catalysts increase reactive species concentration, while base catalysts deprotonate substrates.

Answer 4

Formation of transient covalent bonds between catalytic residues and substrates ## Footnote This stabilizes the transition state and reduces energy required for reactions.

Answer 5

Catalysis through electrostatic interactions between catalyst and substrate ## Footnote Charged residues stabilize charged transition states, lowering activation energy.

Answer 6

reused ## Footnote This characteristic allows enzymes to participate in multiple reactions.

Answer 7

cellular processes, metabolic pathways, and maintaining homeostasis ## Footnote They are essential for life and biological functions.

Answer 8

Bringing substrates close together enhances the likelihood of successful collisions ## Footnote Increases the probability of reacting molecules being in close proximity, promoting efficient catalysis.

Answer 9

Proper alignment of reacting molecules facilitates the formation of the transition state ## Footnote Correct orientation enhances the likelihood of the reaction proceeding, contributing to enzyme catalysis.

Answer 10

* Inorganic ions * Non-protein molecules ## Footnote Examples include metal ions like Mg2+ or Zn2+, which stabilize enzyme structure, participate in substrate binding, or facilitate catalysis.

Answer 11

* Organic, non-protein molecules ## Footnote Examples include vitamin-derived coenzymes like NAD+ or coenzyme A (CoA), which carry and transfer chemical groups, aiding in various enzymatic reactions.

Answer 12

* Each enzyme has an optimal pH for activity * pH affects the ionization state of amino acid side chains ## Footnote Excessive acidity may denature enzymes, altering their three-dimensional structure, and pH changes can inhibit or activate certain enzymes.

Answer 13

TRUE ## Footnote pH levels influence enzyme specificity and activity.

Answer 14

Each enzyme has an optimal temperature for activity ## Footnote Maintaining the appropriate temperature is crucial for sustaining enzyme activity and preventing denaturation.

Answer 15

Multiple interacting binding sites ## Footnote Ligand binding at one site influences subsequent bindings.

Answer 16

Enhances subsequent bindings due to conformational changes ## Footnote It involves the influence of ligand binding at one site on the affinity of subsequent ligands.

Answer 17

Inhibits further bindings, impacting the affinity of subsequent ligands ## Footnote This phenomenon is vital in understanding complex molecular interactions.

Answer 18

Independent binding ## Footnote It measures cooperative binding.

Answer 19

Negative cooperativity ## Footnote A coefficient above 1 indicates positive cooperativity.

Answer 20

Positive cooperativity ## Footnote This reflects enhanced binding affinity due to previous ligand interactions.

Answer 21

Substrate Concentration ## Footnote [S] is a key variable in determining the rate of enzymatic reactions.

Answer 22

Enzyme Concentration ## Footnote [E] is crucial for understanding the dynamics of enzyme activity.

Answer 23

Transition State ## Footnote [ES] is the enzyme-substrate complex formed during the reaction.

Answer 24

Enzymes decrease the activation energy ## Footnote This stabilization of the transition state facilitates the reaction.

Answer 25

Increased saturated enzymes → Vmax ## Footnote This indicates that all active sites of the enzyme are occupied.

Answer 26

E + S «ES → E + P ## Footnote This represents the conversion of substrate to product via the enzyme.

Answer 27

A substance that acts as a biological catalyst ## Footnote Enzymes alter the rate of chemical reactions without altering themselves.

Answer 28

Substance that acts upon the active site of the enzyme ## Footnote The substrate is the reactant that the enzyme acts upon.

Answer 29

Enzyme perfectly binds to its substrate molecule ## Footnote This complex is essential for the catalytic process.

Answer 30

A substance that suppresses the activity of the enzyme ## Footnote Inhibitors can decrease the rate of enzymatic reactions.

Answer 31

Substrate concentration at which the reaction rate is half of the maximum reaction rate ## Footnote It measures E + S binding affinity and indicates the affinity of an enzyme for its substrate.

Answer 32

Higher affinity ## Footnote Km values indicate how tightly an enzyme binds to its substrate.

Answer 33

KM = Kz + K-1 ## Footnote This formula is used to calculate the Michaelis Constant.

Answer 34

No, it is independent of [E] ## Footnote Km remains constant regardless of enzyme concentration.

Answer 35

½ V max ## Footnote This indicates the point at which the reaction rate is half of its maximum.

Answer 36

Max reaction rate with excess [S] and [E] functioning at maximum capacity ## Footnote Vmax occurs when all active sites are bound to substrate, indicating enzyme saturation.

Answer 37

Vmax will double ## Footnote This relationship shows that Vmax is directly proportional to enzyme concentration.

Answer 38

As [S] increases, the rate of reaction approaches Vmax ## Footnote The graph shows that the rate of reaction increases until it reaches maximum velocity.

Answer 39

All active sites are bound to substrate (enzyme is saturated) ## Footnote This indicates that increasing substrate concentration further will not increase the reaction rate.

Answer 40

The rate of enzymatic reactions, specifically the relationship between reaction rate (velocity) and substrate concentration ## Footnote The equation is V = (vmax [S])/(Km+[S]).

Answer 41

V = (vmax [S])/(Km+[S]) ## Footnote This equation describes enzyme reaction rate and kinetic behavior.

Answer 42

The number of substrate molecules converted per second ## Footnote Kcat = vmax/[ET].

Answer 43

Decreased kcat ## Footnote This indicates that higher enzyme concentration can lead to lower catalytic rates.

Answer 44

The effectiveness of a catalyst in accelerating chemical reactions ## Footnote It is measured by Kcat.

Answer 45

In M's' ## Footnote Increased Km leads to decreased catalytic efficiency.

Answer 46

The tendency for dissociation of enzyme and substrate ## Footnote High Ka indicates less binding, while small Ka indicates high affinity.

Answer 47

High affinity because smaller concentration of substrate is required to saturate 50% of the enzyme available ## Footnote This is represented by the equation [ES] -> [E] + [S].

Answer 48

Ka = [E][S]/[ES] ## Footnote This equation helps to understand the binding dynamics between enzyme and substrate.

Answer 49

* Inhibitor competes with substrate for the active site * Resembles substrate structure ## Footnote Competitive inhibitors reduce the rate of substrate binding and are reversible, often overcome by increasing substrate concentration.

Answer 50

* Reduces the rate of substrate binding * Decreased affinity to substrate (Km) * No change in Vmax ## Footnote Competitive inhibitors block the enzyme from substrate binding.

Answer 51

* Inhibitor binds specifically to the enzyme-substrate complex * Binding occurs after substrate binding ## Footnote Uncompetitive inhibitors do not affect substrate binding but reduce the efficiency of catalysis.

Answer 52

* Increased affinity to substrate (Km) * Decreased Vmax * Renders enzyme-substrate complex catalytically inactive ## Footnote Uncompetitive inhibitors affect the enzyme's ability to catalyze reactions.

Answer 53

* Inhibitor binds to an allosteric site on the enzyme * Alters the enzyme's conformation ## Footnote Noncompetitive inhibitors change the enzyme shape, affecting catalytic activity independent of substrate concentration.

Answer 54

* Decreases catalytic activity * No change in Km * Decreased Vmax ## Footnote Noncompetitive inhibitors can bind to either the enzyme or the enzyme-substrate complex with identical affinity.

Answer 55

Inhibitor binds to the enzyme at the active site or an allosteric site ## Footnote Affinity for both the free enzyme and the enzyme-substrate complex.

Answer 56

Alters enzyme conformation, affecting substrate binding and catalysis ## Footnote The impact on substrate binding depends on the inhibitor's preference.

Answer 57

* Noncompetitive: no change in Km * Competitive: changes Km ## Footnote TPC Tip: noncompetitive has no change in Km, while competitive just changes Km.

Answer 58

Pivotal in modulating metabolic pathways, exerting control over cellular activities ## Footnote Example: Digestive enzymes of the pancreas.

Answer 59

Trypsinogen ## Footnote Once in the intestines, it is modified by enterokinase to the active form trypsin.

Answer 60

A regulatory process where a molecule binds to an enzyme at a site other than the active site ## Footnote Binding induces a conformational change in the enzyme, reducing its catalytic activity.

Answer 61

Fine-tuning metabolic pathways and maintaining cellular homeostasis ## Footnote Controls enzymatic activity in response to various signals.

Answer 62

Covalently modified enzymes undergo alterations in their structure through the formation of chemical bonds ## Footnote This modification can significantly impact enzyme activity and function.

Answer 63

Some molecules irreversibly bind to the enzyme's active site, inactivating it, resembling substrate molecules ## Footnote Example: Aspirin irreversibly inhibits cyclooxygenase enzymes involved in inflammation.

Answer 64

Addition of methyl groups to amino acids can alter enzyme activity, impacting processes like gene expression and signal transduction ## Footnote Example: Methylation of histone proteins by histone methyltransferases regulates gene expression.

Answer 65

Acetyl groups are added to enzymes, affecting their charge and structure, influencing activity and protein-protein interactions ## Footnote Example: Acetylation of histones by histone acetyltransferases modulates chromatin structure and gene transcription.

Answer 66

Attachment of sugar molecules can modulate enzyme stability, function, and recognition in cellular processes ## Footnote Example: Addition of sugar moieties to insulin influences its stability and activity in regulating blood glucose.

Answer 67

Addition of phosphate groups by kinases can activate or deactivate enzymes, regulating cellular pathways ## Footnote Example: Phosphorylation of glycogen phosphorylase activates it in the glycogenolysis pathway.

Answer 68

Enzymatic cleavage of proteins can activate or inactivate enzymes, influencing their function and cellular processes ## Footnote Example: Activation of digestive enzymes like trypsin through proteolytic cleavage in the pancreas.

Answer 69

Addition of a phosphate group to an enzyme ## Footnote Phosphorylation can activate or deactivate enzymes.

Answer 70

Addition of an adenyl group to an enzyme ## Footnote This modification can affect enzyme activity.

Answer 71

Addition of a uridine group to an enzyme ## Footnote Uridylylation can influence enzyme function.

Answer 72

Addition of ADP ribose to an enzyme ## Footnote This modification typically activates enzymes.

Answer 73

Addition of a methyl group to an enzyme ## Footnote Methylation can modulate enzyme activity.

Answer 74

Covalent modification ## Footnote Various modifications like phosphorylation or adenylation can activate enzymes.

Answer 75

Covalent modification ## Footnote Modifications such as ADP-ribosylation can enhance enzyme activity.

Answer 76

* Regulatory molecules * Cofactors * Compartmentalization ## Footnote These factors help regulate the metabolism of a cell.

Answer 77

* Activators: molecules that increase enzyme activity * Inhibitors: molecules that decrease enzyme activity ## Footnote These regulatory molecules can bind to enzymes and affect their function.

Answer 78

An inhibitor binds to the active site, blocking substrate binding ## Footnote Competitive inhibitors compete with the substrate for the enzyme's active site.

Answer 79

An inhibitor binds to a different site, blocking enzyme function without blocking substrate binding ## Footnote Noncompetitive inhibitors can bind to the enzyme regardless of whether the substrate is present.

Answer 80

FALSE ## Footnote Noncompetitive inhibitors prevent the enzyme from functioning, regardless of substrate levels.

Answer 81

Regulation where a molecule binds to an enzyme at a site other than the active site ## Footnote This can involve either activation or inhibition of enzyme activity.

Answer 82

Enzymes that have multiple active sites and are regulated by allosteric molecules ## Footnote These enzymes often play key roles in metabolic regulation.

Answer 83

Non-protein helper molecules required for enzyme activity ## Footnote Common cofactors include inorganic ions like iron and magnesium.

Answer 84

Organic molecules that assist enzymes, often derived from vitamins ## Footnote Examples include vitamin C, which acts as a coenzyme for collagen-building enzymes.

Answer 85

To store enzymes in specific cell parts for optimal function and to prevent damage ## Footnote This ensures enzymes are in the right environment to work effectively.

Answer 86

The end product of a metabolic pathway inhibits the key enzyme of that pathway ## Footnote This regulation helps maintain the right amount of product in the cell.

Answer 87

ATP acts as an allosteric inhibitor for enzymes in cellular respiration ## Footnote High ATP levels prevent further ATP production to avoid waste.

Answer 88

ADP acts as a positive allosteric regulator (activator) for some enzymes inhibited by ATP ## Footnote This helps increase enzyme activity when ATP levels are low.

Answer 89

* Competitive inhibitors * Noncompetitive inhibitors * Uncompetitive inhibitors ## Footnote Each type alters enzyme kinetics in distinct ways.

Answer 90

Enzyme kinetics ## Footnote It graphs reaction rate as a function of substrate concentration.

Answer 91

Amount of product produced per unit time at the start of the reaction ## Footnote It is measured when the enzyme and substrate are first combined.

Answer 92

The rate of reaction when the enzyme is saturated ## Footnote It indicates the maximum amount of product produced per unit time.

Answer 93

Substrate concentration giving a reaction rate of half Vₘₐₓ ## Footnote It measures an enzyme's affinity for its substrate.

Answer 94

FALSE ## Footnote Competitive inhibitors increase the apparent Kₘ but do not change Vₘₐₓ.

Answer 95

* Vₘₐₓ: Decreased * Kₘ: Unchanged ## Footnote Noncompetitive inhibitors reduce the effective concentration of functional enzyme.

Answer 96

* Vₘₐₓ: Decreased * Kₘ: Decreased ## Footnote They bind to the enzyme-substrate complex, reducing active complexes.

Answer 97

To visualize differences between kinetic parameters and types of inhibition ## Footnote It provides a linear transformation of the Michaelis-Menten equation.

Answer 98

1/Vₘₐₓ ## Footnote It indicates the maximum velocity of the reaction.

Answer 99

It gets closer to zero ## Footnote This is due to an increase in Kₘ.

Answer 100

Increased 1/Vₘₐₓ ## Footnote It reflects the decrease in Vₘₐₓ due to the inhibitor.

Answer 101

A mechanism where the binding of a molecule at one site affects the binding of other molecules at distant sites ## Footnote This can lead to changes in the enzyme’s shape or conformation, influencing its efficiency.

Answer 102

Cooperativity ## Footnote It is a form of regulation where the binding of a substrate to one site enhances or diminishes the affinity for additional substrate molecules.

Answer 103

Control enzymatic activity in response to fluctuations in substrate concentrations ## Footnote This allows enzymes to be highly sensitive to small changes in their environment.

Answer 104

A quantitative measure of the degree of cooperativity in a system ## Footnote It is derived from the Hill equation, which describes ligand binding to multi-subunit proteins.

Answer 105

Non-cooperative binding ## Footnote Each ligand binds independently of others, typical in enzymes with a single binding site.

Answer 106

Positive cooperativity ## Footnote The binding of one ligand increases the likelihood of additional ligands binding, resulting in an S-shaped substrate-binding curve.

Answer 107

Negative cooperativity ## Footnote The binding of one ligand decreases the affinity for subsequent ligands, flattening the substrate binding curve.

Answer 108

It allows rapid responses to changes in ligand concentrations ## Footnote This is crucial for the efficient function of enzymes like hemoglobin.

Answer 109

Fine-tunes enzyme activity ## Footnote It prevents excessive substrate binding.

ENZYME OVERVIEW Flashcards

(140 cards)