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Plant Physiology > CHAPTER 2: Plant Cell and Enzymes > Flashcards

CHAPTER 2: Plant Cell and Enzymes Flashcards

1
Q

constitute about 30% of the total dry weight of typical plant cells.

A

protein

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2
Q

Proteins and amino acids represent about __ to ___ of the dry weight of the living cell.

A

60 to 70%

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3
Q

If we exclude inert materials, such as the cell wall and starch, which can account for up to ___ of
the dry weight of some cells

A

90%

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4
Q

Major function of proteins in metabolism is to serve as

A

enzymes

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5
Q

greatly increase the rates of biochemical reactions, making life possible

A

enzymes, biological catalysts

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6
Q

Do enzymes change when they participate themselves in processes?

A

They do not change

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7
Q

Enzymes participate
in these reactions but are not themselves ____changed in the process.

A

fundamentally

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8
Q

Enzymes have been called the

A

“agents of life”

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9
Q

The most important features of enzymes are their (2)

A

specificity
catalytic efficiency

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10
Q

Feature of enzyme which permits them to distinguish among very similar molecules

A

specificity

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11
Q

____ are _____ where continuous
synthesis and degradation of molecules happen and hasten by catalysts

A

plants cells
metabolic machineries

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12
Q

Enzymes has the ability to discriminate between similar molecules results from the fact that the first step in enzyme catalysis is the formation of

A

tightly bound, noncovalent complex between the enzyme and the substrate(s)— the enzyme–substrate complex

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13
Q

Enzymes are unique in the ____ ___ ___ they bring about, orders of magnitude greater than those effected by other catalysts

A

large rate enhancements t

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14
Q

enzymes will convert about a thousand molecules of substrate to product in__, while some will convert as many as a _____

A

1 s
million

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15
Q

large protein molecules that increases the rates of chemical reaction without themselves undergoing change

A

Enzyme

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16
Q

Enzyme do not change the position of the _______ ____ but rather increase the reaction rate

A

chemical equilibrium

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17
Q

Two remarkable aspects of enzymes as catalysts:

A

-increasing the reaction rates from 109 to 1020 times
-extremely specific

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18
Q

Enzyme as catalyst are extremely effective by increasing the reaction
rates from ______ to ___ times

A

10^9 to 10^20 times

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19
Q

Enzyme as catalyst are_____, that is, each of them speeding up only __ or ____

A

extremely specific

one particular reaction or class of reactions

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20
Q

Enzymes function at _____ and ________ and usually in a
narrow pH range near _____

A

ambient temperature
atmospheric pressure
neutrality

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21
Q

few enzymes are able to function under ___

A

extremely harsh conditions

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22
Q

protein-degrading enzyme of the stomach (has a pH optimum
around ____)

A

pepsin

2.0

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23
Q

from hyperthermophilic (“extreme heat-loving”) archaebacterium Pyrococcus furiosus; oxidizes H2 at a temperature optimum greater than 950C; the presence of this enzyme in Pyrococcus enables them to grow optimally at 1000C.

A

hydrogenase

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24
Q

hydrogenase – from hyperthermophilic (“extreme heat-loving”) archaebacterium

A

Pyrococcus furiosus

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25
Q

Enzymes are usually named after their __ by the addition of the suffix ____

A

substrates

“-ase”

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26
Q

each enzyme has been named in a systematic fashion, on the basis of the reaction it catalyzes, by the

A

International Union of Biochemistry

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27
Q

the versatility of enzymes reflects their properties as

A

proteins

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28
Q

enzymes are

A

biological catalyst

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29
Q

enzymes are biological catalyst ; they ___ the rate of chemical reactions by taking place ____ without themselves undergoing any change

A

increase

within living cells

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30
Q

reactants of enzyme catalyzed reactions are called as ___ and each enzyme is quite specific in character

A

substrate

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31
Q

enzymes are made of ___with occasional ___ part

A

proteins
non-protein

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32
Q

non-protein component of enzymes

A

cofactors

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33
Q

without cofactors, enzymes will lack their

A

catalytic activity

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34
Q

the protein or polypeptide portion of the enzyme is called

A

apoenzyme

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35
Q

some ____ cannot catalyze a reaction without its ____ and vice versa

A

apoenzyme

cofactor

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36
Q

some cofactors can either be ____ or ____ in nature

A

organic or metallic

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37
Q

____are called as coenzymes which are transiently associated with the
apoenzyme and are themselves changed in the reaction

A

organic cofactors

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38
Q

dehydrogenation reaction
-nicotinamide adenine dinucleotide (NAD+)
-flavin adenine dinucleotide (FAD)

A

NADH and FADH2

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39
Q

metal ion cofactors such as Fe, Mo, Cu, and Zn are sometimes referred to as

A

metal activators

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40
Q

their non-protein co-factors that are more or less permanently associated with the enzyme protein are called

A

prosthetic groups

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41
Q

the compound on which the enzyme works and whose reaction is being speed up is called the

A

substrate

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42
Q

the substrate usually binds to the enzyme surface while it undergoes the reaction on a specific portion called the

A

active site

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43
Q

can also be found on active sites

A

coenzymes

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44
Q

enzymes are able to catalyze or speed up particular reactions because they _____required to initiate the reaction

A

lower the amount of activation energy

45
Q

catalysis occurs at the active site which is composed of the__ and ___

A

binding site and the catalytic group

46
Q

site of the enzyme where the substrate molecules bind and
undergo the chemical reaction

A

active site

47
Q

active site of an enzyme contains ___ ____ ____ ____ that form temporary bonds with the substrate

A

specific amino acid residues

48
Q

active site of the enzyme occupies ____ of the total volume of the
enzyme

A

~10 – 20%

49
Q

active site is the most important part of the enzyme that catalyzes the

A

chemical reactions

50
Q

he active site of the enzyme contains only __ to ____

A

three to four amino acids

51
Q

location of substrates binding with the enzyme; one of the two
components of the active site of the enzyme; bind and orient substrate molecules

A

binding site

52
Q

location where the catalysis of the chemical reaction occurs in the
enzyme

A

catalytic site

53
Q

the _____in the catalytic site of the enzyme are responsible
for catalyzing the chemical reaction

A

amino acids

54
Q

catalytic site ____ the activation energy of the chemical reaction

A

reduces

55
Q

____ is one of the two main components of the active site of an enzyme

A

catalytic site

56
Q

the main function of an enzyme is to catalyze a chemical reaction under

A

physiological conditions

57
Q

refers to a location on a macromolecule or cellular structure at which chemical
interaction with a specific active substance takes place temporarily binds with the substrate binds and orients the substrate

A

binding site

58
Q

refers to a portion of an enzyme molecule at which the actual reaction proceeds and is considered to consist of one or more residues or atoms in a spatial arrangement catalyzes the reaction of the substrate reduces the chemical activation energy

A

catalytic site

59
Q

Six major classifications of enzymes

A

-(HOT ILL)
-hydrolases
-oxidoreductases
-transferases

-isomerases
-lyases
-ligases/synthetases

60
Q

The suffix – ase identifies a ____ as an enzyme

A

substance

61
Q

The type of reaction catalyzed is often noted with a

A

prefix

62
Q

The substrate is often

A

noted

63
Q

Enzyme Naming (3)

A
  1. The suffix – ase identifies a substance as an enzyme.
  2. The type of reaction catalyzed is often noted with a prefix.
  3. The substrate is often noted. -
64
Q

enzymes are ___ ____protein catalysts for each enzyme has its own uniquely shaped active site which is specific to certain type of substrate

A

highly specific

65
Q

accordingly, two model were proposed that showed how specific enzymes are including the (2)

A

Induced-Fit Model

66
Q

a model for enzyme-substrate interaction in which the active site of the enzyme does not
completely fit to the substrate

A

induced fit model

67
Q

Enzyme-substrate interaction in which the active site of the enzyme completely fits with the substrate

A

lock and key model

68
Q

induced fit model was suggested by

A

Daniel Koshland

69
Q

lock and key model was suggested by

A

Emil Fischer

70
Q

The active site of the enzyme does not completely fit with the substrate in the

A

induced fit model

71
Q

active site of the enzyme precisely fits with the substrate in the

A

lock and key model

72
Q

In this model, the active site of the enzyme has to undergo a conformational change to improve binding

A

induced fit model

73
Q

model that describes the specificity of the active site of the enzyme to a particular substrate.

A

lock and key model

74
Q

The active site of the enzyme contains two components in the

A

induced fit model

75
Q

the active site of the enzyme contains a single entity in the

A

lock and key model

76
Q

model where there is a separate catalytic group in the enzyme

A

induced fit model

77
Q

model where there is no separate catalytic group in the enzyme

A

lock and key model

78
Q

Model where the active site of the enzyme is not static

A

induced fit model

79
Q

Model where the active site of the enzyme is static in

A

lock and key model

80
Q

transition state develops before the reactants undergo changes in the

A

induced fit model

81
Q

a transition state does not develop before the reactants undergo changes in the

A

lock and key model

82
Q

Catalytic group weakens the substrate bonds either by the nucleophilic or electrophilic attack in the

A

induced fit model

83
Q

the catalytic group does not weaken the substrate bonds in the

A

lock and key model

84
Q

describes the mechanism of nonaction over competitive inhibitors

A

induced fit model

85
Q

describes the specificity of the active site of the enzyme to a particular substrate

A

lock and key model

86
Q

_____ explains the specificity of enzyme action by comparing the
active site of an enzyme to a lock and the substrate to a key, however, this model
assumes that the enzyme is ___, ____

A

Lock-and-Key Model

rigid, three-dimensional body

87
Q

compares the active site to a glove and the substrate to a hand,
that is, like a glove to a hand that accommodates the shape of the substrate

A

Induced-Fit Model

88
Q

reaction rates depend on the number of ____ __ ____ between substrate and enzyme molecules, which in turn depends upon their concentrations

A

successful collisions

89
Q

Factors affecting the Enzyme Activity and Inhibition (3)

A

-Enzyme and Substrate Concentrations
-Temperature
-pH

90
Q

if we keep the concentration of the substrate constant, an increase in enzyme concentration would linearly increase the rate of enzyme activity

A

substrate

91
Q

if we keep the concentration of the _____ constant and increase the
concentration of the substrate, there is a different scenario since rate does not increase continuously

A

enzyme

92
Q

there is a point where the rate stays the same even with increase
substrate concentration called as th

A

saturation point

93
Q

at _____, substrate molecules are bound to all available active
sites of an enzyme

A

saturation point

94
Q

increasing _____increases the ____ with which the enzyme and substrate collide

A

substrate concentration

frequency

95
Q

Because of the increased collision of enzyme and substrate, enzyme-substrate complexed _______ and the rate of reaction ____

A

form more quickly

increases

96
Q

there is a limit as eventually there all the enzyme active sites are already occupied with substrate - the enzyme active sites become

A

saturated

97
Q

any further increase in substrate concentration has __ ____ ____ on the reaction rate

A

no further effect

98
Q

increasing the amount of _____also increases the _____ of with which the enzyme and substrate collide

A

enzyme
frequency

99
Q

some enzymes become_____as they won’t have any substrate to bind

A

redundant

100
Q

affects enzyme activity because of denaturation or the alteration of the three-dimensional structure of the enzyme

A

temperature

101
Q

Causes denaturation or alteration making the substrate not be able to fit to active sites

A

temperature

102
Q

influences the ionization of substrates, denaturation state, and presence of charged
and uncharged free amino or carboxyl groups in the enzyme

A

pH

103
Q

a neutral carboxyl group requires a ____ optimum while an uncharged amino group needs a ____ optimum

A

low pH

high pH

104
Q

any process that makes an active enzyme less active or inactive

A

inhibition

105
Q

Inhibition is any process that makes an active enzyme less active or inactive which is
accomplished by compounds known as

A

inhibitors

106
Q

Two types of Inhibitors:

A

-Competitive Inhibitors
-Non-competitive Inhibitors

107
Q

bind to the active site of an enzyme surface, thereby, preventing the real substrate to bin

A

-Competitive Inhibitors

108
Q

binds to some portion of the enzyme surface which may
sufficiently alters the tertiary structure of the enzyme so that its catalytic effectiveness is
slowed down

A

Non-competitive Inhibitors

109
Q

Both competitive and noncompetitive inhibitors are ____, but some compounds alter the structure of the enzyme permanently and thus, make it ___ _____.

A

reversible

irreversibly inactive

Plant Physiology (4 decks)

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