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Clinical Chemistry (CC 1) > (F) L1: Enzymes (Part 1) > Flashcards

(F) L1: Enzymes (Part 1) Flashcards

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1
Q

Enzymes hasten chemical reactions in (organic/inorganic) matter as they are biologic catalysts

A

Organic

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2
Q

TOF: Enzymes are capable of catalyzing multiple chemical reactions which serve as the basis for their classification

A

False (single/limited amount)

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3
Q

Enzymes are large molecules found (inside/outside) the cell

A

Inside

Note: They are involved in the processes within the cell

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4
Q

Increased membrane permeability allows enzymes to (enter/exit) the blood

A

Enter

Note: This allows for their measurement in the lab

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5
Q

TOF: Enzymes are measured directly (their absolute value in the blood sample)

A

False (measured in terms of activity)

Note: You don’t measure how much enzyme is present in the sample

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6
Q

Enzymes appear in serum after cellular (growth/injury)

A

Injury

Note: They also appear after cellular degeneration or from storage areas

It’s because they are found INSIDE the cell

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7
Q

If enzymes are found in the serum, it most likely correlates to what?
A. Organ damage
B. Organ regeneration
C. Organ transplant

A

A. Organ damage

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8
Q

Enzymes are specific for their what in order to convert it into a defined product?

A

Substrates

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9
Q

Enzymes tend to react with a number of substrates which can lead to what reaction?

A

Cross-reactivity

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10
Q

What do you call the reaction wherein an enzyme only reacts with one substrate?

A

Absolute Reaction

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11
Q

This is a water-free cavity where the substrate interacts/binds with

A

Active Site

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12
Q

This is a cavity other than the prior site which binds regulator molecules

A

Allosteric Site

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13
Q

In order to catalyze certain reactions, enzymes are required to first bind to a substrate which produces what complex?

A

Enzyme-Substrate (ES) Complex

Note: Only then will the enzyme release/produce a product

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14
Q

This refers to when enzymes stay intact after the synthesis of products

A

Reusability of the enzyme

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15
Q

Factors Affecting Enzymatic Reactions

In enzyme concentrations, the higher the concentration, the (faster/slower) the reaction

A

Faster

Note: A higher # of enzymes can accomodate more substrates

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16
Q

Factors Affecting Enzymatic Reactions

This principle states that when the substrate concentration reaches its maximal value, higher concentration substrates no longer result in increased rate of reaction

A

Saturation Kinetics

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17
Q

Factors Affecting Enzymatic Reactions

S1: The rate of reaction will decrease when additional substrates are added
S2: When all enzymes are occupied, the additional substrates will remain functional and the rate of reaction will remain steady

Which among the statements is true?

A

Both are false

S1: Will increase
S2: Substrates will be deemed useless

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18
Q

Cofactors

  • These are your second substrates
  • A higher value of this signifies an increased reaction velocity
  • Is in combination with a cofactor and apoenzyme
  • Is essential for absolute enzymatic activity

e.g. NAD and NADP

A

Coenzyme

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19
Q

Cofactors

Which among the 2 is the inactivated enzyme and the active enzyme?

A. Holoenzyme
B. Apoenzyme

A
  1. Inactivated = Apoenzyme
  2. Activated = Holoenzyme
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20
Q

Cofactors

What is formed when:
Cofactor + Apoenzyme + Coenzyme

A

Holoenzyme

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21
Q

Cofactors

The more coenzyme present, the (higher/lower) the velocity of the reaction

A

Higher (meaning “faster”)

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22
Q

Cofactors

Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP) are considered?

A. Apoenzymes
B. Holoenzymes
C. Coenzymes

A

C. Coenzymes

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23
Q

Cofactors

  • These are inorganic ions (Ca, Zn, Cl, Mg, and K)
  • They alter the spatial configuration of the enzyme for proper binding
  • Are mostly electrolytes
A

Activators

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24
Q

Cofactors

  • These are inorganic ions attached to a molecule
  • Can act as enzymes themselves even though they aren’t called as such
  • e.g. Catalase and Cytochrome Oxidase
A

Metalloenzymes

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25
Q

These inhibit enzymatic reactions

A

Inhibitors

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26
Q

Types of Inhibitors

  • This assembles in the form of a substrate compatible with a specific enzyme allowing it to bind to the active site
  • It competes for the same site against the original substrate
  • The reaction is reversible
  • Can result to an excess in substrates
  • Can decrease the velocity of the reaction (Km)
A

Competitive Inhibitor

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27
Q

Types of Inhibitors

Refers to the the property of being able to be removed from the active site which gives the substrate a chance to retrieve its original site

A

Reversibility

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28
Q

Types of Inhibitors

Why do inhibitors result in an excess in substrate?
A. More substrates are released in the presence of inhibitors
B. Binding sites are occupied by the inhibitors
C. Binding sites select the inhibitors more than the substrates

A

B. Binding sites are occupied by the inhibitors

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29
Q

Types of Inhibitors

A graphical representation of saturation kinetics

A

Michaelis-Menten Curve

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30
Q

Types of Inhibitors

  • Refers to the substrate concentration at which the reaction velocity is half of the maximum level
  • It is constant for a specific enzyme and substrate under a defined reaction condition
  • An expression of the relationship between the velocity of an enzymatic reaction and substrate concentration
A

Michaelis-Menten Constant

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31
Q

Types of Inhibitors

  • Refers to the the relationship between the rate of reaction and the substrate
  • States that the rate of reaction will initially increase as more substrate is added but will later remain constant when the maximum level is reached
A

Saturation Kinetics

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32
Q

Types of Inhibitors

TOF: In the presence of competitive inhibitors, the velocity (Km) changes

A

True

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33
Q

Types of Inhibitors

  • This does not compete with the substrate since it targets the allosteric site
  • It alters the shape of the active site which prevents binding of the substrate thereby decreasing the reaction
  • The action is irreversible
A

Non-competitive Inhibitors

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34
Q

Types of Inhibitors

  • This binds to an ES complex rather than the enzyme
  • An increase in substrate leads to an increase in ES complexes thereby increasing inhibition
A

Uncompetitive Inhibitors

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35
Q

Types of Inhibitors

What type of inhibitor is this referring to?

Competes for the same site

A

Competitive

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36
Q

Types of Inhibitors

What type of inhibitor is this referring to?

Targets the allosteric site

A

Non-competitive

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37
Q

Types of Inhibitors

What type of inhibitor is this referring to?

Binds to an ES complex

A

Uncompetitive

38
Q

Types of Inhibitors

What type of inhibitor is this referring to?

The reaction is reversible

A

Competitive

39
Q

Types of Inhibitors

What type of inhibitor is this referring to?

The reaction is irreversibe

A

Non-competitive

40
Q

Types of Inhibitors

What type of inhibitor is this referring to?

It alters the shape of the active site

A

Non-competitive

41
Q

Factors Affecting Enzymatic Reactions

  • These are variations of one enzyme which provides minute changes in the characteristics of each
  • It provides the same catalytic reaction but has a slightly different molecular structure which varies in amino acid sequences
A

Isoenzymes

42
Q

Factors Affecting Enzymatic Reactions

TOF: Isoenzymes make it easier to isolate the activity of the target enzyme

A

False (more difficult)

Note: A single substrate may react with ALL of the isoenzymes making it non-specific

43
Q

Factors Affecting Enzymatic Reactions

TOF: Isoenzymes increase enzymatic activity

A

True

44
Q

Factors Affecting Enzymatic Reactions

S1: Isoenzymes have an indirectly proportional relationship with enzymatic activity
S2: Isoenzymes have a directly proportional relationship with the easiness of isolating the activity of the target enzyme

Which of these statements is false?

A

Both are false (reverse the relationships)

45
Q

Factors Affecting Enzymatic Reactions

What is the optimum temperature for enzymatic activity?

A

37ºC

Note: 25º, 30º, and 37º is the range of values

46
Q

Factors Affecting Enzymatic Reactions

At what temperatures are enzymes denatured resulting in a decreased rate of reaction?

A

40-50ºC

47
Q

Factors Affecting Enzymatic Reactions

At what temperatures are enzymes inactivated?

A

60-65ºC

48
Q

Factors Affecting Enzymatic Reactions

An increase in temperature increases the movement of what resulting in an increased rate of reaction?

A

Molecules

49
Q

Factors Affecting Enzymatic Reactions

What is this principle: For every 10ºC increase, there is a two-fold increase (2x) in enzymatic activity

A

Temperature Coefficient (Q10)

50
Q

Factors Affecting Enzymatic Reactions

What is the optimum pH for enzymatic physiologic reactions?

A

Between 7-8

51
Q

Factors Affecting Enzymatic Reactions

An extreme pH level may result to the ff. EXCEPT:
A. Denaturation
B. Alteration of the covalent state of the enzyme
C. Structural changes
D. Changes in the charge of amino acid residues

A

B. (should be ionic state)

52
Q

Factors Affecting Enzymatic Reactions

These are used to stabilize the pH for enzymatic reactions

A

Buffers

53
Q

Factors Affecting Enzymatic Reactions

Complete the statements to make them true:
1. Storing enzymes at low temperatures will make them (reversibly/irreversibly) inactive
2. Refrigeration/freezing is an (ideal/undesirable) way of storing enzymes with the exception of LDH
3. Repeated thawing and freezing will result to (denaturation/inhibition)

A
  1. Reversibly
  2. Ideal
  3. Denaturation
54
Q

Factors Affecting Enzymatic Reactions

LDH is stored ideally at RT especially its coenzymes LD4 and LD5 as they are (heat-labile/cold-labile)

A

Cold-labile

Note: May lead to falsely decreased values

55
Q

Factors Affecting Enzymatic Reactions

Fill in the missing numerical values:
1. A prolonged preservation will require a temperature of atleast (blank)
2. Temperatures of (blank) to (blank) are the ideal storage temperatures for substrates and coenzymes

A
  1. -20ºC
  2. 2ºC to 8ºC
56
Q

Factors Affecting Enzymatic Reactions

When there is hemolysis, enzymes are released into the circulation and will result to a falsely (increased/decreased) enzyme concentration

A

Increased

57
Q

Factors Affecting Enzymatic Reactions

This factor refers to the example of the presence of TAGs which decreases enzyme concentration

A

Lactescence or Milky specimen

58
Q

Enzyme Nomenclature

  1. 1st Digit
  2. 2nd/3rd Digit
  3. 4th Digit

A. Serial number
B. Classification
C. Subclass

A
  1. B
  2. C
  3. A
59
Q

Enzyme Nomenclature

This was standardized by what organization?

A

Enzyme Commission (EC)

60
Q

Enzyme Nomenclature

Enzymes are classified according to the ff. EXCEPT:
A. Biochemical function
B. Substrate catalyzed
C. Class of reaction catalyzed
D. Activation energy

A

D. Activation energy

61
Q

Enzyme Classification

Function: The removal or addition of electrons (redox)
Examples: Cytochrome oxidase (CO), Lactate dehydrogenase (LDH), Malate dehydrogenase (MDH), Isocitrate dehydrogenase (ICD), and G6PD

A

Oxidoreductase

62
Q

Enzyme Classification

Function: The transfer of a chemical group other than hydrogen from one substrate to another
Examples: Creatine kinase (CK), Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), and Ornithine transcarbamylase (OTC)

A

Transferase

63
Q

Enzyme Classification

Function: The hydrolysis or splitting of a bond by the addition of water
Examples: Esterase, Acid phosphatase (ACP), Alkaline phosphatase (ALP), Chalcone synthase (CHS), and Lipase (LPS)

A

Hydrolase

64
Q

Enzyme Classification

Function: The removal of groups from substrates without hydrolysis with products containing double bonds
Examples: Glutamate decarboxylase, Pyruvate decarboxylase, Tryptophan decarboxylase, and Aldolase (ALD)

A

Lyase

65
Q

Enzyme Classification

Function: Catalyze the intramolecular arrangement of the substrate compound
Examples: Glucose phosphate isomerase and Ribose phosphate isomerase

A

Isomerase

66
Q

Enzyme Classification

Function: The joining of two substrate molecules coupled with the breaking of pyrophosphate bonds in ATP or similar compounds
Examples: Synthase

A

Ligase

67
Q

Enzyme Theories

  • Presented by Emil Fisher
  • The shape of the substrate must fit into the enzyme
A

Lock and Key Model

68
Q

Enzyme Theories

  • Presented by Kochland
  • The substrate binds to the active site of the enzyme (gives emphasis on the presence of the active site)
A

Induced Fit Theory

69
Q

Enzyme Kinetics

Greater amount of free energy in the substrate + lesser amount of free energy on the product = ?

Note: Free energy = kinetic energy

A

Increased chemical reaction

70
Q

Refers to the ability of an enzyme to react to a specific substrate

A

Enzyme Specificity

71
Q

Enzyme Specificity

  • It combines with only one substrate and catalyzes only one reaction
  • The most preferred as it directly measures the target enzyme/substrate
A

Absolute Specificity

72
Q

Enzyme Specificity

This combines with all the substrates in a chemical group

A

Group Specificity

73
Q

Enzyme Specificity

This reacts with specific chemical bonds

A

Bond Specificity

74
Q

Enzyme Reactions

  • This depends on enzyme concentration
  • Methods of determining these are expensive hence the preference for the other kind of reaction
A

Zero-order

75
Q

Enzyme Reactions

  • Is directly proportional to substrate concentration
  • e.g. a decrease in the number of substrate indicates a decrease in the number of enzymes
A

First-order

76
Q

General Methods of Assay

  • Enzymes will be measured once on a designated time
  • Reactants will first be combined, then a reaction will take place on a designated time
  • The reaction will be stopped and measured
A

Fixed Time (Endpoint Method)

77
Q

General Methods of Assay

Multiple measurements are done and is more preferred over fixed time

A

Continuous Monitoring (Kinetic Assay)

78
Q

Units for Enzymatic Activity

  • The conventional unit
  • 1 micromole of substrate per minute (umol/min)
A

International Unit (IU or U)

79
Q

Units for Enzymatic Activity

  • 1 mole of substrate per second (mol/sec)
  • 1 IU = 16.7 or 17 of this unit
  • 1 of this unit = 0.06 IU/L
A

Katal Unit (KU)

80
Q

TOF: Since most laboratories utilize the enzyme itself in measuring enzyme levels, the units for enzymatic activity focuses more on its concentration

A

False (amount of substrate)

Remember: Enzymes are quantified based on their activity rather than absolute values

81
Q

Enzymes are quantified based on their activity which depends on the ff. EXCEPT:

A. A change in substrate concentration
B. A change in product concentration
C. A change in apoenzyme concentration

A

C. (must be coenzyme)

82
Q

Units used to report enzyme levels are called as?

A

Activity Units

Must consider a change in pH, temperature, substrate, etc.

83
Q

Causes of Elevated Plasma Levels

Impaired removal of enzymes from (serum/plasma) which may be related to renal function

e.g. Amylase is freely-filtered in the kidneys therefore damage in the kidneys may cause problems regarding its removal

A

Plasma

84
Q

Causes of Elevated Plasma Levels

(Increased/Decreased) cell membrane permeability

A

Increased

85
Q

Causes of Elevated Plasma Levels

Increase in the production of (cells/stimulating hormones) such as malignancies and the like

A

Cells (↑ cells = ↑ enzymes)

86
Q

Causes of Elevated Plasma Levels

(Increased/Decreased) cell turnover/apoptosis

A

Increased

Note: Early destruction may lead to increased enzymes in the circulation

87
Q

Causes of Elevated Plasma Levels

Decreased (clearance/release) of enzymes from the circulation may be related to renal function

A

Clearance

88
Q

Causes of Elevated Plasma Levels

(Cell/Tissue) necrosis and degeneration due to external factors

A

Tissue

89
Q

Familiarize with the 10 factors affecting enzymatic reactions

A
  1. Enzyme concentration
  2. Substrate concentration
  3. Cofactors
  4. Inhibitors
  5. Isoenzymes
  6. Temperature
  7. Hydrogen ion concentration (pH)
  8. Storage
  9. Hemolysis
  10. Lactescence/milky specimen
90
Q

Familiarize with the 6 causes of elevated plasma enzyme levels

A
  1. Impaired removal of enzyme from plasma
  2. Increased permeability of cell membrane
  3. An increase in the number of cells or the production of cells such as malignancies and the like
  4. An increase in the normal cell turnover or apoptosis
  5. Decreased clearance of enzymes from the circulation
  6. Tissue necrosis and degeneration

Clinical Chemistry (CC 1) (22 decks)

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