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Biochemistry > Metabolism (General) > Flashcards

Metabolism (General) Flashcards

1
Q

Active holoenzymes are formed from
____________ in the presence of
_________.
a. Cofactors; proteins
b. Proteins; cofactors
c. Apoenzymes; cofactors
d. Apoenzymes; proteins
e. Apoenzymes; inactive holoenzymes

A

c. Apoenzymes; cofactors

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2
Q

Define Metabolism

A

the entire network of chemical reactions carried out by living cells

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3
Q

Define Metabolites

A

small molecule intermediates in the degradation and synthesis of polymers

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4
Q

Catabolic reactions

A

Degrade molecules to create smaller molecules and energy

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5
Q

Anabolic reactions

A

synthesize molecules for cell maintenance, growth and reproduction

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6
Q

Metabolic Pathways

A
  • branched and interconnected (networked)
  • Networking is arbitrary and driven by chemical logic
  • Catabolic reactions generate energy and anabolic reactions use energy
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7
Q

Cell Organelles and Metabolic Functions:

1- Mitochondria
2-Cytosol
3- Lysosomes
4- Golgi Complex
5- Endoplasmic reticulum
6- Peroxisomes (plants)

A

1- Mitochondrion: TCA cycle, Oxidative Phosphorylation, fatty acid oxidation, Amino acid breakdown

2- Cytosol: Glycolysis, Fatty acid biosynthesis, gluconeogenesis

3- Lysosomes: Degradation of cell components
Nucleus-DNA replication, Transcription, RNA processing

4- Golgi Complex: Synthesis of membrane components

5- Endoplasmic reticulum: Synthesis of proteins

6- Peroxisomes (plants): Oxidative reactions in plants

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8
Q

The metabolism of the four major groups of biomolecules will be considered:

A

Carbohydrates
Lipids
Amino Acids
Nucleotides

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9
Q

Flux

A

flow of material through a metabolic pathway which depends upon:
(1) Supply of substrates (2) Removal of products (3) Pathway enzyme activities

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10
Q

Feed-back inhibition:

A

Product of a pathway controls the rate of its own synthesis by inhibiting an early step (usually the first “committed” step (unique to the pathway)

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11
Q

Feed-forward activation:

A

Metabolite early in the pathway activates an enzyme further down the pathway

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12
Q

Interconvertible enzyme activity can be rapidly and reversibly altered by..

A

covalent modification

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13
Q

Three types of compounds are produced that mediate the release of energy

A

(1) Acetyl CoA
(2) Nucleoside triphosphates (e.g. ATP)
(3) Reduced coenzymes (NADH, FADH2, QH2)

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14
Q

Oxidative phosphorylation

A

is the process by which the potential is coupled to the reaction: ADP + Pi —> ATP

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15
Q

ΔG=ΔH–TΔS

A

Gibbs free energy

Cells must work within the laws of thermodynamics

There are three cases
∆G < 0: the reaction proceeds as written
∆G = 0: the reaction is at equilibrium
∆G > 0: the reaction runs in reverse

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15
Q

ΔG=ΔH–TΔS

A

Gibbs free energy

Cells must work within the laws of thermodynamics

There are three cases
∆G < 0: the reaction proceeds as written
∆G = 0: the reaction is at equilibrium
∆G > 0: the reaction runs in reverse

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16
Q
  • Has 3 phosphoryl groups
  • Hydrolysis releases large amount energy
  • Energy release is accompanied by transfer of phosphoryl group to another compound
  • Hence, biologically important molecule
A

ATP-A High Energy Intermediate

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17
Q

Formation of glucose 6-phosphate from glucose is an example of ——– reaction

A

Coupled Reactions

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18
Q

Formation of ATP from ADP is an example of ——– reaction

A

Coupled Reactions

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19
Q

Metabolic Pathways that occurs in Cytosol

A

Glycolysis

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20
Q

Metabolic Pathways that occurs in Mitochondria

A

Oxidative Phosphorylation

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21
Q

Operation of different metabolic pathways at different compartments occurs in ———— cells

A

Eukaryotic cells

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22
Q

All of the reactions take place in the same compartment but localized to different areas

A

prokaryotic cells

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23
Q

Compartmentalization of metabolic processes permits:

A
  • separate pools of metabolites within a cell
  • simultaneous operation of opposing metabolic paths
  • high local concentrations of metabolites
  • coordinated regulation of enzymes

Example: fatty acid synthesis enzymes (cytosol), fatty acid breakdown enzymes (mitochondria)

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23
Q

Compartmentalization of metabolic processes permits:

A
  • separate pools of metabolites within a cell
  • simultaneous operation of opposing metabolic paths
  • high local concentrations of metabolites
  • coordinated regulation of enzymes

Example: fatty acid synthesis enzymes (cytosol), fatty acid breakdown enzymes (mitochondria)

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24
Q

Compartmentalization is ————-specific

A

tissue and organ

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25
Q

Gluconeogenesis and detoxification occurs in which organ?

A

Liver

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26
Q

Storage of triglycerides occurs in which tissue?

A

Adipose tissue

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27
Q

LDH Type M present in…

A

skeletal muscle and liver

-Pyruvate to Lactate

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28
Q

LDH Type H present in…

A

heart muscle

-Lactate to Pyruvate

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29
Q

Organisms extract energy from ——– to drive energy-consuming reactions

A

external sources

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30
Q

T or F
Cells are not static

A

T
cell components are continually synthesized and degraded
(i.e. undergo turnover)

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31
Q

Organisms or cells maintain specific internal concentrations of…

A

inorganic ions, metabolites and enzymes

32
Q

Three Metabolic Pathways and they are……

A

(a) Linear
(b) Cyclic
(c) Spiral pathway

33
Q

———————— permit control of energy input and output

A

Multiple-step pathways

34
Q

Catabolic multi-step pathways provide energy in ——————

A

smaller stepwise amounts

35
Q

———- occur in multi-step pathways

A

Control points

36
Q

Metabolism is ———– to permit organisms to respond to changing conditions

A

highly regulated

37
Q

Most Metabolic pathways are….

A

irreversible

38
Q

Metabolic fuels:

A

(1) Carbohydrates: provide energy
(2) Proteins: provide amino acids for protein synthesis and some energy
(3) Fats: triacylglycerols provide energy and also lipids for membrane synthesis

39
Q

Active holoenzymes are formed from
____________ in the presence of
_________.
a. Cofactors; proteins
b. Proteins; cofactors
c. Apoenzymes; cofactors
d. Apoenzymes; proteins
e. Apoenzymes; inactive holoenzymes

A

c. Apoenzymes; cofactors

40
Q

Because coenzymes are specific for
the chemical groups that they accept
and donate, they are referred to as
a. Cofactors
b. Reactive centers
c. Activator ions
d. Group-transfer reagents
e. All of the above

A

d. Group-transfer reagents

41
Q

Ca2+ or Mg2+ are most likely to be
part of ___________, while Zn2+ or Fe2+
are present in _______________.
a. Metal-activated enzymes;
metalloenzymes
b. Metalloenzymes; metal-activated
enzymes
c. Cofactors; coenzymes
d. Coenzymes; cofactors
e. Apoenzymes; holoenzymes

A

a. Metal-activated enzymes;
metalloenzymes

42
Q

Coenzymes which must return to
their original form after each
catalysis are called
a. Prosthetic groups
b. Cosubstrates
c. Metabolite coenzymes
d. Vitamin coenzymes
e. All of the above

A

e. All of the above

43
Q

Intermediary metabolism is the term
applied to reactions that
_______________.
a. degrade molecules
b. synthesize large molecules such
as proteins
c. convert glucose to pyruvate
d. involve low molecular weight
metabolites

A

d. involve low molecular weight
metabolites

44
Q

Which statement is not true about
catabolic pathways?
a. They have a net release of
energy.
b. They have a net consumption of
ATP.
c. They liberate smaller molecules
from larger ones.
d. They include the citric acid
cycle.

A

b. They have a net consumption of
ATP.

45
Q

A distinct set of metabolic
reactions is called a reaction
________________.
a. microcosums
b. cycle
c. pathway
d. mechanism

A

c. pathway

46
Q

Consider the synthesis of a
biopolymer in which the addition of
successive monomers occurs by the same
kind of reaction(s). The synthesis of
the polymer is a ________ pathway.
a. linear
b. cyclic
c. spiral
d. branched

A

c. spiral

47
Q

Which statement is false about
most metabolic pathways?
a. Most pathways are reversible
under physiological conditions.
b. Pathways serve to increase the
efficiency of energy transfers.
c. The rates of pathway reactions
vary to respond to changing
conditions.
d. The enzymes that catalyze
reactions in metabolic pathways
generally catalyze only a single
step.

A

a. Most pathways are reversible
under physiological conditions.

48
Q

The flow of material through a
metabolic pathway is called the
________.
a. current
b. degree of amplification
c. cascade effect
d. flux

A

d. flux

49
Q

The flow of material through a
reaction pathway usually depends on
________________.
a. control at several steps in the
pathway
b. control of the first step of the
pathway
c. covalent modification of the
enzyme that catalyzes the reaction
d. feed-forward activation

A

a. control at several steps in the
pathway

50
Q

For a step in a reaction pathway
to serve as a control point it should
be ____________.
a. irreversible
b. endergonic
c. far from equilibrium
d. both a and c
e. all of the above

A

d. both a and c

51
Q

Ten people are sitting in a row.
Their objective is to whisper a secret
from one person to the next all the
way down the row. The first person
whispers the secret to the second
person who passes the secret to the
third person and so on. After
whispering to the third person, the
second person in the row notices the
ninth person has fallen asleep in
their chair, so she gets up, goes down
the row and shakes person nine awake.
This example is similar to ________.
a. allosteric control
b. positive cooperativity
c. feed-forward activation
d. negative modulation

A

c. feed-forward activation

52
Q

Which is usually the slowest way
to regulate a reaction in a metabolic
pathway?
a. allosteric modulation
b. covalent modification
c. changing the enzyme
concentration
d. all of the above are usually
equally as fast

A

c. changing the enzyme
concentration

53
Q

The ultimate product of complete
oxidation of carbohydrates is
__________.
a. carbon dioxide
b. acetyl CoA
c. pyruvate
d. acetate ion

A

a. carbon dioxide

54
Q

Which distinguishes a steady state from an equilibrium?
a. In a steady-state the
concentrations of intermediates
vary; in an equilibrium they do
not.
b. A steady-state requires constant
removal of product and
replenishment of reactant; an
equilibrium does not.
c. Steady-state and equilibrium are
not distinguishable. They are two
terms for the same thing.
d. Steady-states apply only to
irreversible reactions. Equilibrium
reactions must be reversible.

A

b. A steady-state requires constant
removal of product and
replenishment of reactant; an
equilibrium does not.

55
Q

Calculate Delta G
0’ for the
reaction shown if the mass action
ratio, Q, is 5.3 x 102 M
-1 and Delta G
is 46 kJ/mol at a temperature of 298
K. (R = 8.315 J/K-mol)
ADP + Pi –> ATP
a. 30 kJ/mol
b. -30 kJ/mol
c. 61 kJ/mol
d. -61 kJ/mol

A

a. 30 kJ/mol

56
Q

A reaction that best serves as a
control point for regulation
_______________.
a. is a near equilibrium reaction
b. has a large positive Delta G
c. is metabolically irreversible
d. follows Michaelis-Menton
kinetics

A

c. is metabolically irreversible

57
Q

The amount of energy recovered
as ATP can be estimated by measuring
free energy of hydrolysis of
a. Phosphoester I bond in ATP
b. Phosphoanhydride bonds in ADP
c. Phosphoester bond I ADP
d. Phosphoanhydride bonds in ATP
e. All of the above

A

d. Phosphoanhydride bonds in ATP

58
Q

ATP is the most commonly used
source of energy rich compounds in
cells because
a. It complexes with Mg2+
b. It has a higher free energy of
hydrolysis
c. Its products of hydrolysis are
more stable the ATP
d. It is used more often than other
nucleoside triphoshates
e. It engages in phosphoryl-group
transfers

A

d. It is used more often than other
nucleoside triphoshates

59
Q

Which of the following is not a
factor contributing to the large free
energy of hydrolysis of ATP?
a. Electrostatic repulsion of
oxygen atoms
b. Better solvation of products
than ATP itself
c. Complexes with Mg2+ or Mn2+ ions
d. Better stability of products
than ATP itself
e. Electrical sheilding of products
of hydrolysis

A

c. Complexes with Mg2+ or Mn2+ ions

60
Q

ATP can be used to activate a
substrate by
a. Phosphorylation
b. Adding a nucleotidyl group
c. Producing inorganic phosphate
d. Both a and b
e. a, b, and c

A

d. Both a and b

61
Q

A compound with a greater free
energy of hydrolysis than ATP is
a. Glucose 1-phosphate
b. Any phosphoester
c. Phosphoenolpyruvate
d. Acetyl CoA
e. All of the above

A

c. Phosphoenolpyruvate

62
Q

ATP is thermodynamically suited
as a carrier of phosphoryl groups in
animal cells because
a. It is stable under cell
conditions
b. It is not hydrolyzed in cells
without enzyme action
c. It is intermediate in grouptransfer potential
d. It can be produced from
phosphocreatine
e. All of the above

A

e. All of the above

63
Q

The formation of acetyl CoA is
brought to completion because
a. The standard free energy for the
first reaction is negative
b. The standard free energy for the
final reaction is negative
c. The product pyrophosphate is
readily removed by pyrophosphatase
d. The formation of an ADP
intermediate is negative
e. All of the above

A

c. The product pyrophosphate is
readily removed by pyrophosphatase

64
Q

The chemical energy generated by
oxidations cannot be captured by
a. NADH
b. NADP
c. FMN
d. FAD
e. Q

A

a. NADH

65
Q

When a reduction half-reaction
is __________ (negative, positive),
electrons flow to the more readily
reduced substance which is __________
(negative, positive) in value.
a. Negative; negative
b. Negative; positive
c. Positive; positive
d. Positive; negative

A

b. Negative; positive

66
Q

The biochemical reactions that
degrade molecules, such as nutrients,
are called anabolic reactions.
a. True
b. False

A

b. False

67
Q

A given cell type tends to
maintain relatively constant internal
concentrations of inorganic ions,
enzymes and metabolites.
a. True
b. False

A

a. True

68
Q

Metabolic pathways generally
have easily distinguished starting and
stopping points.
a. True
b. False

A

b. False

69
Q

Most metabolic reactions occur
continuously at a fixed rate.
a. True
b. False

A

b. False

70
Q

Phosphatases catalyze the
hydrolytic removal of phosphate
groups.
a. True
b. False

A

a. True

71
Q

Metal-activated enzymes may
require a metal ion or simply be
stimulated in the presence of the ion.
a. True
b. False

A

a. True

72
Q

Vitamin deficiency diseases are
a result of the lack of formation of
certain coenzymes.
a. True
b. False

A

a. True

73
Q

Phosphorylation of enzymes
involved in catabolic pathways usually
activates them.
a. True
b. False

A

a. True

74
Q

All enzymes require metallic
cations to achieve full catalytic
activity.
a. True
b. False

A

b. False

75
Q

All metabolic reactions occur in
the cytosol of cells.
a. True
b. False

A

b. False

76
Q

Reactions of most metabolic
pathways are in a state of equilibrium
and have a Delta G equal to zero.
a. True
b. False

A

b. False

77
Q

Protein catalysts rely
exclusively on the amino acid residues
for reactivity at the sites of action.
a. True
b. False

A

b. False

78
Q

Organic compounds are coenzymes
and cofactors while inorganic ions are
cofactors only.
a. True
b. False

A

b. False

Biochemistry (10 decks)

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