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Biomolecules > Metabolic Pathways > Flashcards

Metabolic Pathways Flashcards

1
Q

1 g of carbohydrate is equal to what kcal

A

1 kcal

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2
Q

increases the chemical reaction significantly

A

catalyst

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3
Q

are the biochemicals that come together and interact at the beginning of the
process such that they are converted into one or more different biochemicals

A

reactants

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4
Q

temporary state wherein they become or processed futher

A

intermediates

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5
Q

reactants can become ___ if the next step is a branching point

A

common intermediates

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6
Q

refer to a chemical that participates as one of the starting chemicals in a
chemical reaction that produces other substance(s).

A

precursor

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7
Q

” is used more specifically to refer to a
chemical compound preceding another in a metabolic pathway.

A

precursor

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8
Q

e types of proteins that play an important role in metabolism by catalyzing the
individual reactions in metabolic pathways.

A

enzymes

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9
Q

Enzymes that catalyze the first reaction in a metabolic pathway are sometimes subject to
___ control by the concentration of the end product of the metabolic pathwa

A

allosteric

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10
Q

” is a word used in chemistry generally (not just biochemistry) to refer to chemicals
that affect the rate (speed) of chemical reactions by participating in the reaction(s) but in
such a way that itis not consumed by the reaction itself.

A

catalyst

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11
Q

, the presence of a
___ may be necessary for a reaction to occur to any meaningful extent under certain
conditions

A

catalyst

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12
Q

are compounds that are neither the initial (starting) chemicals in a pathway or
“process”, nor the end-products used directly or secreted by the cell, nor catalysts (that
participate in but are not used-up by the reactions)

A

intermediates

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13
Q

are compounds
that are formed as temporary “steps” in the overall chemical process

A

intermediates

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14
Q

are compounds that occur at branching points in metabolic
pathways.

A

common intermediates

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15
Q

are compounds that are produced by metabolic
reactions that do not go on to participate in a subsequent reaction in the metabolic pathway.

A

end products

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16
Q

The concentration of the end products of a metabolic pathway often regulates the rate of the
reaction that produces them, i.e. effectively a ___ that prevents over-production

A

feedback loop

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17
Q

inhibition or activation of an enzyme by a small regulatory molecule that interacts at a site other than the active site

A

allosteric control

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18
Q

is a form of negative feedback by which metabolic pathways can be controlled.

A

end product inhibition

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19
Q

Some branching points in metabolic pathways are sometimes called

A

cross-over points

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20
Q

s refer to a stage in a metabolic pathway at which an intermediate
(usually a molecule or part of a molecule), could proceed to change in more than one
possible way, i.e. it could follow two or more possible “(metabolic) pathways”.

A

branching points

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21
Q

The “pathway” followed (next change undergone) by the intermediate is usually the one of
most immediate benefit to the cell, that “decision” being determined by the activity of
____ present around the intermediate.

A

enzyme

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22
Q

is a position at which at least two “paths” intersect

A

junction

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23
Q

implies that the intersection is particularly important, i.e.
one at which decisions taken about which on-going paths to follow from that point onwards
may change depending on circumstances and have important consequences.

A

key junction

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24
Q

are substances (usually compounds) that participate in metabolism processes
and are either produced during metabolism reactions or are “constituents of” i.e. parts that
make-up, foods taken into the body - then broken-down via the digestive
processes

A

metabolites

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25
Q

are therefore among the chemicals included in metabolic pathways.
They are often intermediates between reactants and end-products.

A

metabolites

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26
Q

metabolites that are molecules that are essential for an organism’s growth, development, and reproduction:

A

primary metabolites

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27
Q

metabolites that are organic compounds produced by organisms that are not essential for the organism’s growth, development, or reproduction.

A

secondary metabolites

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28
Q

is the descriptive term used to refer to some metabolic pathways or parts
of metabolic pathways that take the form of repeated ‘cycles’ in which product(s) of the
individual metabolic reactions in the sequence become the reactants, i.e. the “starting
chemicals”, for the next metabolic reaction in the sequence.

A

metabolic cycles

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29
Q

metabolic cycles include

A

Krebs TCA Cycle
Calvin cycle
Urea cycle

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30
Q

” is a point at which many “pathways” meet. These could be routes, wires,
lines of communication or similar e.g. as used in the context of air-travel or information
technology

A

hub

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31
Q

can therefore be thought of as a location at which many metabolic
processes occur, enabling substances such as molecules, e.g. reaction intermediates, to
transfer between reaction processes on an as-needed basis.

A

metabolic hub

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32
Q

example of metabolic hubs in the body

A

krebs TCA cycle
liver

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33
Q

generally modify biochemicals via a series of small steps (stages in the process) rather
than a single chemical reaction

A

metabolic pathways

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34
Q

Minor adjustments can be made to the structure of the molecules.
Energy is released / used in manageable quantities.

what characteristic of metabolic pathway

A

metabolic pathways generally modify biochemicals via a series of small steps

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35
Q

Many balances - i.e. requirements for specific enzymes - keep the rate of metabolic processes in
check.

what characteristic of metabolic pathways

A

each step in a metabolic pathway is a chemical rxn that can catalyze a specific enzyme

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36
Q

Benefit: The biochemical reactions at each stage of a metabolic pathway are more likely to proceed (that is,
continue to happen) because the products of that particular reaction do not accumulate because they go on
to participate in the next step in the metabolic pathway … which changes them into other biochemical(s).

what characteristic of metabolic pathways

A

chemical equilibrium may never be reached because the products of reactions do not continue to exist in that form due to participation of nexts step

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37
Q

one that is not part of a metabolic pathway but is
considered entirely on its own - the meaning of “isolated”. In that case only a certain proportion of the
reactants may be converted into the products of the reaction due to a natural “equilibrium” situation at which
a certain proportion of the total matter concerned is in the form of the reactants and a certain
(other) proportion in the form of the products of the reaction

A

isolated chemical rxn

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38
Q

Benefit: Accumulation of concentrations of biomolecules that are the reactants of a step in a metabolic
pathway can help to increase the rate (i.e. the “speed”) of the process. This is related to the above
considerations of “equilibrium”.

what metabolic pathway characteristic

A

Steps in a metabolic pathway tend to be arranged in physical space such that the product of one reaction is
in the right place to become a reactant (or “precursor”) in the next step in the sequence.

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39
Q

is the metabolic pathway that converts glucose C6H12O6, into pyruvic acid, CH3COCOOH

A

glycolysis

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40
Q

does glycolysis require oxygen?

A

no

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41
Q

an ancient metabolic pathway

A

glycolysis

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42
Q

parallel pathway of glycolysis

A

pentose phosphate pathway

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43
Q

what metabolic pathway, occur in the oxygen-free conditions of the Archean oceans, also in the absence of enzymes, catalyzed by
metals

A

glycolysis
pentose phosphate pathway

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44
Q

two phases of glycolysis

A

investment phase
yield phase

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45
Q

The first step is phosphorylation of glucose by a family of enzymes called ___ to form glucose 6-phosphate (G6P).

A

hexokinase

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46
Q

This reaction consumes ATP, but it acts to keep the glucose concentration low, promoting continuous transport of glucose into
the cell through the plasma membrane transporters.

A

conversion of glucose to glucose 6-phosphate

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47
Q

In addition, the conversion of glucose to glucose-6 phosphate blocks the glucose from leaking out because ___

A

the cell lacks
transporters for G6P, and free diffusion out of the cell is prevented due to the charged nature of G6P

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48
Q

why free diffusion of glucose 6-phosphate is not possible

A

charged

49
Q

Glucose may
alternatively be formed from the ____ or hydrolysis of intracellular starch or glycogen.

A

phosphorolysis

50
Q

Glucose may
alternatively be formed from the phosphorolysis or hydrolysis of intracellular ___ or ___.

A

starch
oxygen

51
Q

is a biochemical process that breaks down chemical bonds in a compound using inorganic phosphate

A

phosphorolysis

52
Q

In animals, an isozyme of hexokinase called ___ is also used in the liver, which has a much lower affinity for glucose
(Km in the vicinity of normal glycemia), and differs in regulatory properties

A

glucokinase

53
Q

The different substrate affinity and alternate
regulation of this enzyme are a reflection of the role of the liver in maintaining blood sugar levels.

A

glucokinase

54
Q

G6P is then rearranged into fructose 6-phosphate (F6P) by what enzyme

A

glucose phosphate isomerase

55
Q

can also enter the
glycolytic pathway by phosphorylation at this point.

A

fructose

56
Q

The change in structure is an ____ , in which the G6P has been converted to F6P

A

isomerization

57
Q

This reaction is freely reversible under normal cell conditions

what step in glycolysis

A

conversion of F6P to G6P

58
Q

The change in structure is an isomerization, in which the G6P has been converted to F6P. The reaction requires an enzyme,
phosphoglucose isomerase, to proceed. This reaction is freely reversible under normal cell conditions. However, it is often
driven forward because of a low concentration of ___

A

F6P

59
Q

under
conditions of high F6P concentration, this reaction readily runs in reverse. This phenomenon can be explained through what principle

A

Le Chatelier principle

60
Q

Isomerization to a keto sugar is necessary for ____stabilization in the fourth reaction step

A

carbanion

61
Q

. Because the reaction catalyzed by _____
1 (PFK-1) is coupled to the hydrolysis of ATP (an energetically favorable step)

A

phosphofructokinase

62
Q

rate limiting step in glycolysis, a key regulatory point

A

phosphofructokinase coupled with the hydrolysis of ATP

63
Q

s necessary to allow the formation of two charged groups (rather than only
one) in the subsequent step of glycolysis, ensuring the prevention of free diffusion of substrates out of the cell.

A

second phosphorylation event

64
Q

The same reaction can also be catalyzed by pyrophosphate-dependent ____ (PFP or PPi-PFK), which is
found in most plants, some bacteria, archea, and protists, but not in animals

A

phosphofructokinase

65
Q

phosphofructokinase uses what phosphate donor instead of ATP

A

pyrophosphate

66
Q

is the conversion using phosphofructokinase reversible?

A

yes

67
Q

Destabilizing the molecule in the previous reaction allows the hexose ring to be split by aldolase into two triose
sugars: dihydroxyacetone phosphate (a aldose/ketose), and glyceraldehyde 3-phosphate (an aldose/ketose)

A

ketose
aldose

68
Q

two classes of aldolases

A

class I
class II

69
Q

aldolases present in animals nad plants

A

aldolases I

70
Q

aldolases present in fungi and bacteria

A

class II aldolases

71
Q

is a glycolytic enzyme that catalyzes the conversion of fructose 1-6-diphosphate to glyceraldehyde 3-phosphate and dihydroxy-acetone phosphate via the glycolysis metabolic pathway

A

aldolase

72
Q

The resulting carbanion is
stabilized by the structure of the carbanion itself via ___ charge distribution and by the presence of a charged ion
prosthetic group.

A

resonance

73
Q

rapidly interconverts dihydroxyacetone phosphate with glyceraldehyde-3-phosphate (GADP) that
proceeds further into glycolysis.

A

triosephosphate isomearase

74
Q

The second half of glycolysis is known as the

A

pay-off phase

75
Q

yield of pay-off phase of glucose

A

2 NADH
4 ATP

76
Q

The aldehyde groups of the triose sugars are oxidized/reduced, and inorganic phosphate is added to them, forming 1,3-
bisphosphoglycerate.

A

oxidized

77
Q

Hydrogen atom balance and charge balance are both maintained because the phosphate (Pi) group actually exists in the form
of a h

A

hydrogen phosphate anion

78
Q

an anion akin to inorganic phosphate may replace phosphate as a substrate to form 1-arseno-3-
phosphoglycerate.

A

arsenate

79
Q

As a consequence of bypassing this step, the molecule of ATP generated from 1-3
bisphosphoglycerate in the next reaction will not be made, even though the reaction proceeds. As a result, arsenate is an
___ of glycolysis

A

uncoupler

80
Q

This step is the enzymatic transfer of a phosphate group from 1,3-bisphosphoglycerate to ADP by

A

phosphoglycerate kinase

81
Q

what enzyme is used to turn G3P to 1,3-bisphosphoglycerate

A

gylceraldehyde 3-phoshpate dehydrogenase

82
Q

. This step, one of the two substrate-level phosphorylation steps,requires ADP; thus, when the cell has plenty of ATP (and little ADP), this reaction does not occur.

A

glycolysis reaching a breakeven point of 2 ATP molecules synthesized

83
Q

enzyme to convert 1,3-bisphosphoglycerate to 3-phosphoglycerate

A

phosphoglycerate mutase

84
Q

next converts 2-phosphoglycerate to phosphoenolpyruvate

A

enolase

85
Q

This reaction is an elimination reaction involving an
elimination mechanism.

A

reaction of 2-phosphoglycerate to phosphoenolpyruvate

86
Q

A final substrate-level phosphorylation now forms a molecule of pyruvate and a molecule of ATP by means of the
enzyme

A

pyruvate kinase

87
Q

e, is a series of chemical
reactions that release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

A

citric acid cycle

88
Q

e is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either
by anaerobic respiration or aerobic respiration

A

TCA cycle

89
Q

Its central importance to many biochemical
pathways suggests that it was one of the earliest components of metabolism and may have originated abiogenically.

A

krebs cycle

90
Q

The cycle consumes ___(in the form of acetyl-CoA) and water, reduces NAD+
to NADH, releasing carbon dioxide.

A

acetate

91
Q

The cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+
to NADH, releasing ___ ___

A

carbon dioxide

92
Q

In eukaryotic cells, the citric acid cycle occurs in the

A

matrix of mitochondrion

93
Q

In prokaryotic cells, such as bacteria, which
lack mitochondria, the citric acid cycle reaction sequence is performed in the

A

cytosol

94
Q

In prokaryotic cells, such as bacteria, which
lack mitochondria, the citric acid cycle reaction sequence is performed in the cytosol with what gradient

A

proton gradient

95
Q

The
overall yield of energy-containing compounds from the TCA cycle

A

3 NADH
1 FADH2
one GTP

96
Q

is a key metabolic pathway that connects carbohydrate, fat, and protein metabolism.

A

citric acid cycle

97
Q

One of the primary sources of acetyl-CoA is from the breakdown of sugars by glycolysis which yield pyruvate that in turn is
decarboxylated by the ___ ___ complex generating acetyl-CoA

A

pyruvate dehydrogenase

98
Q

is the starting point for the citric acid cycle. A

A

acetyl coA

99
Q

e. Acetyl-CoA may also be obtained from
the oxidation of __ ___

A

fatty acids

100
Q

The citric acid cycle begins with the transfer of a two-carbon acetyl group from acetyl-CoA to the four-carbon
acceptor compound (____) to form a six-carbon compound (citrate)

A

oxaloaceatate

101
Q

The citric acid cycle begins with the transfer of a two-carbon acetyl group from acetyl-CoA to the four-carbon
acceptor compound (oxaloacetate) to form a six-carbon compound (____)

A

citrate

102
Q

The citrate then goes through a series of chemical transformations, losing two carboxyl groups as ___

A

CO2

103
Q

enzyme for conversion of Oxaloactetate + Acetyl coA + H2O to Citrate + CoA-SH

A

citrate synthase

104
Q

how many carbons does oxaloacetate have

A

4C

105
Q

citrate has how many carbons

A

6C

106
Q

enzyme for Citrate > isocitrate

A

aconitase

107
Q

enzyme for isocitrate > ketoglutarate

A

isocitrate dehydrogenase

108
Q

how many carbons does ketoglutarate have

A

5

109
Q

enzyme for ketoglutarate > succinyl coA

A

a-ketoglutarate dehydrogenase

110
Q

how many c does succincyl CoA have

A

4

111
Q

enzyme for succinyl coA to succinate

A

succinyl CoA synthethase

112
Q

enzyme for succinate > fumarate

A

succinate dehydrogenase

113
Q

enzyme for fumarate > malate with the help of H2O

A

fumarase

114
Q

enzyme for malate > oxaloacetate

A

malate dehydrogenase

115
Q

Mitochondria in animals, including humans, possess ___ succinyl-CoA synthetases: one that produces GTP from GDP, and
another that produces ATP from ADP

A

two

116
Q

what are the products of succinyl coA synthethases in animals

A

GTP from GDP
ATP from ADP

117
Q

. Plants have the type that produces what kind of succincyl coA synthethase

A

ATP

118
Q

The GTP that is formed by GDP-forming succinyl-CoA synthetase may be utilized by ___ ___ ____to form
ATP (the catalyzed reaction is GTP + ADP → GDP + ATP).

A

nucleoside disphosphate kinase

Biomolecules (23 decks)

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