Download lecture CH23 chem131pikul

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CHAPTER 23: Metabolism & Energy Production
Learning Objectives:
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CH 23 Homework:
End of Chapter problems: 20, 22, 24, 26, 28, 32, 34, 36, 40, 42, 46, 48,
50, 52, 56, 60, 64, 74(
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Metabolism
Definition
• Metabolism is the sum of all the chemical
reactions that take place in an organism.
• Catabolism is the breakdown of large
molecules into smaller ones; energy is
generally released during catabolism.
Anabolism is the synthesis of large
molecules from smaller ones; energy is
generally absorbed during anabolism.
• Often, the process is a series of
consecutive reactions called a metabolic
pathway, which can be linear or cyclic.
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Metabolism
P(
Overview
Stage [1] – Digestion
Stage [2] – Formation of Acetyl CoA
Stage [3] – The Citric Acid Cycle
Stage [4] – Electron Transport Chain
& Oxidative Phosphorylation
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Metabolism
Stage [1] – Digestion
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Metabolism
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Stage [2] – Formation of Acetyl CoA
S(
Metabolism
Stage [3] – The Citric Acid Cycle
• The citric acid cycle is based in the
mitochondria, where the acetyl CoA is
oxidized to CO2.
• The cycle also produces energy stored as
a nucleoside triphosphate and the reduced
coenzymes.
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Metabolism
T(
Stage [4] – Electron Transport Chain
& Oxidative Phosphorylation
• Within the mitochondria, the
electron transport chain and
oxidative phosphorylation
produce ATP (adenosine 5 triphosphate).
• ATP is the primary energycarrying molecule in the body
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Definition
ATP
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Hydrolysis: Energy Released
ATP
• Hydrolysis of ATP cleaves 1 phosphate group.
• This forms ADP and hydrogen phosphate (HPO42!),
FIRST
PAGES
releasing 7.3 kcal/mol
of energy.
757
ATP AND ENERGY PRODUCTION
O
−O
ATP AND ENERGY PRODUCTION
P
O
O
O−
P
O−
FIRST PAGES
O
P
−O
P
O−
O
P
O−
O
P
O−
O
CH2
N
N
−O
P
O−
H2O
N
O
O
N
+
O−
N
O
N
O
NHOH
2
O
O
N
O
This bond is broken.
O
NH2
NH2
This bond is broken.
O
P
O
CH2
N
757
O
NHOH
2
ATP
O
−O
O
N
OH
NADP
O
N
+
O−
OH
N
−O
P
OH
−
O
Pi
O
N
O P O CH2
O
Any process, such asP walking,
running, swallowing,
orNbreathing, is fueled by the release
−O
−
−
+ most
P OH member of a group
O of ATP to ADP. ATP is the
O
from the hydrolysis
prominent
of “high-energy” molecules, reactive molecules that release energyO−by cleaving a bond during
OH
OH
OH
OH
hydrolysis. Because ATP contains four negatively charged oxygen atoms in close proximity, the
electronic
repulsion of the like charges drives
ATP
ADP the hydrolysis to ADP,Piwhich has fewer negatively
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oxygens and therefore less electronic repulsion.
Any process, such as walking, running, swallowing, or breathing, is fueled by the release
• The reverse
reaction,
phosphorylation,
adds
a phosphate
group
ADP, forming ATP.
of energy from the hydrolysis
of ATP
to ADP.
ATP is the most
prominent
member
of atogroup
Phosphorylation
requiresthat
7.3release
kcal/mol
of energy.
of “high-energy” molecules,
reactive molecules
energy
by cleaving a bond during
hydrolysis. Because ATP contains four negatively charged oxygen atoms in close proximity, the
CH2
O
N
N
+
Hof
2Oenergy
NH2
This bond is formed.
NH
O−
O−
O−
coupled
reaction.
(b)
TP AND ENERGY PRODUCTION
+
OH
This bond is broken.
fructose
O−
H O
+
757
O−
2
How much energy is released
in the coupled reaction?
OH
OH
NH2
N
O
P
OH
−
O
OH
Energy change
HPO42−ATP
+
−
fructose 6-phosphate
+
H2O
NH2
+3.8ADP
kcal/mol
N
N
Pi
N
O
O
Any process, such as walking,
running,
swallowing, or breathing, is fueled by the release
Phosphorylation:
Energy
Absorbed
−
−
O member of a group
of
energy
from
the
hydrolysis
of
ATP
to
ADP.
prominent
P
O
CH2 ATP
O
P
O
O P O P O P O CH2
N
O
O is theNmost N
Write the equation for the hydrolysis
of
ATP
to
ADP
(Section
23.3A).
Add
together
the
substances
in
−
of
“high-energy”
molecules,
reactive
molecules
that
release
energy
by
cleaving
−
−
−
−
−
+
O P OH a bond during
+ H2O
O
O
O
O
O
this equation and the given hydrolysis.
equation
to
give
the
net
equation—that
is,
the
equation
for
the
coupled
Because ATP contains four negatively charged oxygen atoms in close
proximity, the
O−
reaction. To OH
determine
energy
change,
add
together
the energy
changes
each
step.
OHthe overall
OH hydrolysis
OH to for
electronic
repulsion
of
the
like
charges
drives
the
ADP,
which
has
fewer
negatively
• Phosphorylation is the reverse reaction, where
charged oxygens and therefore less electronic repulsion.
O
O
O
ATP N
Analysis
Solution
ATP
ADP
a phosphate
group is added to ADP, forming
ATP
Pi
a. The coupled equation shows
overall
reaction
that combines
phosphorylation
of fructose
• The the
reverse
reaction,
addsthe
a phosphate
group to ADP,
forming ATP.
requiring
7.3
ofphosphorylation,
energy.
Any process,
such
askcal/mol
walking, running,
orenergy.
breathing, is fueled by the release
Phosphorylation
requires swallowing,
7.3 kcal/mol of
and the hydrolysis
of ATP.
of energy from the hydrolysis of ATP to ADP. ATP is the most prominent member of a group
Cross out
compounds
that
appear
of “high-energy” molecules,NH
reactive
molecules
that
release energy
bybond
cleaving
a bond during
NH2
This
ison
formed.
2
both sidescharged
of the reaction
arrows.
hydrolysis. Because ATP contains four negatively
oxygen atoms
in close proximity, the
N
N
N 2− drives the hydrolysis to ADP, which has fewer negatively
N
of the+likeHPO
charges
O
O
O
O
Oelectronic
[1] repulsion
fructose
fructose
6-phosphate
+ H2O
4
charged
oxygens
and
therefore
less
electronic
repulsion.
−
−O
N
O P O P O P O CH
P O P O CH
2
O−
N
O
Phosphorylation requires 7.3 kcal/mol of energy.
OH
Coupled reaction:
−O
P
OH
fructose
NH2
ADP
+
ATP
fructose 6-phosphate
This bond is formed.
P
b. The overall energy change is the sum of thei energy changes for each step:
N
N
+3.8 kcal/mol + (–7.3) kcal/mol
–3.5reactions,
kcal/mol.ATP
O of energy.
O is a transporter
O
O
By way of=these
O
O
O−
P
O
CH
2
O
PROBLEM
23.3
O
−
N
O
2
N
−
−+
ATP + +H2O
ADP
HPO 2−
HPO42− adds a phosphate
O−group
Oto
O • The[2]
reverse reaction, phosphorylation,
ADP,Oforming ATP. 4
−
N
N
+
−O
P
O
P
O
P
OH
O
NH
ATP 2
N
• Energy
in ATP
when
it is synthesized from ADP.
2− is absorbed and stored
−
−
−
HPO4
O
O
O
N
N
+
H2O
The phosphorylation of glucose
to glucose
1-phosphate
requires
5.0 to
kcal/mol
of energy. This
• Energy
is released
when ATP is
hydrolyzed
ADP.
unfavorable
the equation
for the
OH reaction
OH can be driven by the hydrolysis of ATP to ADP. (a) WriteOH
OH
Figureenergy
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summarizes
and energy
changes that occur when ATP is synthesized
coupled reaction. (b) How much
is releasedthe
in reactions
the coupled
reaction?
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Pi
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and hydrolyzed.
As we learned in Section 6.2, whenATP
energy is released in a reaction, the
2–
glucose
+ change
HPO4 is reportedglucose
1-phosphate
+ H2so
O the energy change for ATP hydrolysis
energy
as a negative
(–) value,
By way of these reactions, ATP is a transporter of energy.
is –7.3 kcal/mol. When energy is absorbed in a reaction, the energy change is reported as a
positive (+) value, so the energy change for the phosphorylation of ADP is +7.3 kcal/mol. The
• Energy
absorbed
stored in ATP
it isdrawn
synthesized
ADP.
Coupled reactions
that is
use
ATP orand
coenzymes
arewhen
often
usingfrom
a combination
of horizontal
synthesis of ATP with HPO42– is the reverse of ATP hydrolysis, and the energy changes for
• Energy
released when
ATP is
hydrolyzed
to products
ADP.
and curved arrows.
Theisprincipal
organic
reactants
and
are
drawn
from
left
to right with
such reactions are equal in value but opposite in sign.
a reaction arrow as usual, but additional compounds like ATP and ADP are drawn on a curved
Figure 23.4 summarizes the reactions and energy changes that occur when ATP is synthesized
arrow. This technique
is meant
organic
substrates
of isthereleased
reaction,
making
and
hydrolyzed.
Asto
weemphasize
learned
in the
Section
6.2,
when energy
in awhile
reaction,
the
Coupled
Reactions
ATP
it clear that other
materials
neededas23.4
for
theATP
reaction
to occur.
energy
change isare
reported
a negative
(–) value,
so the
energy change for ATP hydrolysis
Figure
Hydrolysis
and
Synthesis
is –7.3 kcal/mol. When energy is absorbed in a reaction, the energy change is reported as a
Energy change
ADP for ATP
OPO
O
positive (+) value, so
the32−
energy change
the phosphorylation
of ADP is +7.3 kcal/mol.
The
ATP Hydrolysis2–
ATP +
H2O
ADP + HPO42−
−7.3 kcal/mol
synthesis of ATP with HPO4− is the reverse of ATP hydrolysis, and
the
energy
changes
for
CH
C COO
CH3 C COO−
such reactions 2are equal in value but opposite in sign.
2−
ATP Synthesis
phosphoenolpyruvate
ADP
+
HPO4
pyruvate
+
ATP
H2O
+7.3 kcal/mol
Energy is released.
Figure are
23.4pairs
ATP Hydrolysis
and Synthesis
PROBLEM
• Coupled23.4
reactions
of reactions
that occur
Energy is absorbed.
together.
Write each of the following reactions using curved arrow symbolism.
Energy change
• The energy
released
by toone
is absorbed
the
other
reaction.
2−
Hydrolysis
HPO
+ reaction
H2O
ADPandby
+ADP
−7.3
kcal/mol23.1)
4
a. reaction of ATP
fructose
with ATPATP
form
fructose
6-phosphate
(Sample
Problem
b. reaction of glucose with ATP to form glucose
6-phosphate and ADP
2−
ATP energetically
Synthesis
ADP unfavorable
+ HPO4
ATPwith
+ a favorable
H2O
+7.3 kcal/mol
• Coupling an
reaction
one that
releases more energy than the amount required
is
common
in
biological
Energy is released.
Energy is absorbed.
reactions.
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H2O
OH
ADP
N
CH2
O
+
+
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Coenzymes
Oxidation & Reduction
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Coenzymes
VP(
Coenzyme A
• Coenzyme A (HS-CoA) is neither an oxidizing
nor a reducing agent.
• When the thioester bond is broken, 7.5 kcal/mol
of energy is released.
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Citric Acid
Cycle
Overview
• The citric acid cycle produces high-energy compounds
for ATP synthesis in stage [4] of catabolism.
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Citric Acid
Cycle
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Overview
VS(
Citric Acid
Cycle
Steps 1 - 4
• Step [1] reacts acetyl CoA with oxaloacetate to form
citrate, and it is catalyzed by citrate synthase.
• Step [2] isomerizes the 3o alcohol in citrate to the 2o
alcohol in isocitrate; it is catalyzed by aconitase.
• Step [3] isocitrate loses CO2 in a decarboxylation reaction
catalyzed by isocitrate dehydrogenase. Also, the 2o alcohol
of isocitrate is oxidized by the oxidizing agent NAD+ to form
the ketone !-ketoglutarate and NADH
• Step [4] releases another CO2 with the oxidation of !ketoglutarate by NAD+ in the presence of coenzyme A to
form succinyl CoA and NADH. Catalyzed by !-ketoglutarate
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dehydrogenase
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Citric Acid
Cycle
Steps 5 - 8
• Step [5] the thioester bond of succinyl CoA is hydrolyzed to
form succinate, releasing energy that converts GDP to GTP.
• Step [6] succinate is converted to fumarate with FAD and
succinate dehydrogenase; FADH2 is formed.
• Step [7], water is added across the C=C; this transforms
fumarate into malate, which has a 2o alcohol.
• Step [8], the 2o alcohol of malate is oxidized by NAD+ to
form the ketone portion of oxaloacetate and NADH. The
product of step [8] is the starting material for step [1].
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Citric Acid
Cycle
Overall Reaction
The main function of the citric acid cycle is to
produce reduced coenzymes (NADH and FADH2).
These molecules enter the electron transport chain
and ultimately produce ATP.
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Electron
Transport
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Definition
• The electron transport chain is a multistep
process using 4 enzyme complexes (I, II, III and IV)
located along the mitochondrial inner membrane.
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Electron
Transport
Electron Transport Chain
• The reduced coenzymes (NADH and FADH2) are
reducing agents, and can donate e! when oxidized.
• NADH is oxidized to NAD+ and FADH2 is oxidized
to FAD when they enter the electron transport
chain.
• The e! donated by the coenzymes are passed
down from complex to complex in a series of
redox reactions, which produces some energy.
• These e! and H+ react with inhaled O2 to form water.
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ATP Synthesis
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Oxidative Phosphorylation
• The electron transport chain provides the energy
to pump H+ ions across the inner membrane
of the mitochondria.
• The concentration of H+ ions in the inter membrane
space becomes higher than that inside the matrix
creating a potential energy gradient.
• To return to the matrix, H+ ions travel through a
channel in the ATP synthase enzyme (catalyzes
phosphorylation of ADP to ATP).
• The energy released as the H+ ions return to the
matrix is the energy stored in the ATP molecule.
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ATP Synthesis
Oxidative Phosphorylation
• Each NADH entering the electron transport chain
produces enough energy to make 2.5 ATPs.
• Each FADH2 entering the electron transport chain
produces enough energy to make 1.5 ATPs.
• The citric acid cycle produces overall:
3 NADH x 2.5 ATP = 7.5 ATP
1 FADH2 x 1.5 ATP = 1.5 ATP
1 GTP =
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ATP Synthesis
1 ATP
10 ATP
;P(
Oxidative Phosphorylation
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