L1,Citric acid cycle
L2,Electron transport and oxidative
hosphorylation
L3,Photosynthesis
Section L Respiration and Energy
? Role
? Location
? The cycle
? Energy yield
? Regulation
? Biosynthetic pathways
Citric acid cycle
Role
? The citric acid柠檬酸 cycle,also known as the
TCA (tricarboxylic acid三羧酸 ) cycle or Krebs
cycle (after its discover in 1993),is used to
oxidize the pyruvate formed during the glyco-
lytic breakdown of glucose into CO2 and H2O,
The cycle is a major energy source in the form
of ATP and also produces precursors for many
biosynthetic pathways,
Location
? The citric acid cycle occurs
within the mitochondria of
eukaryotes and the cytosol of
prokaryotes,
The cycle
? Step 1,Oxidation of fuel molecules to acetyl CoA
? A major source of energy is glucose which is
converted by glycolysis into pyruvate,Pyruvate
dehydrogenase (a complex of three enzymes and five
coenzymes ) then oxidizes the pyruvate (using NAD+
which is reduced to NADH ) to form acetyl CoA and
CO2 since the reaction involves both an oxidation and
a loss of CO2,the process is called oxidative
decarboxylation,
Acetyl-CoA
? The cycle carries out the oxidation
of acetyl groups from acetyl CoA to
CO2 with the production of four
pairs of electrons,stored initially in
the reduced electron carriers NADH
and FADH2
The citric acid cycle
Cycle mode
EIGHT STAGES
? The citric acid cycle has eight stages,
? (1)Production of citrate from oxaloacetate (草
酰乙酸 ) and acetyl CoA (catalyzed by citrate
synthase)
? COOH CH3 CH2-COOH
? CO + CO HO-C-COOH
? CH2 S CH2-COOH
? COOH CoA
Citrate formation
Isomerization (异构化作用 )of citrate to
isocitrate (catalyzed by aconitase 顺乌头酸酶 )
? CH2-COOH CH2-COOH
? HO-C-COOH H-C-COOH
? CH2-COOH HO-CH-COOH
Isocitrate formation
Oxidation of isocitrate to α –ketoglutarate（ α-酮
戊二酸,catalyzed by isocitrate dehydrogenase;
the reaction requires NAD+ ）
? COOH COOH
? CH2 CH2
? H-C-COOH CH2
? HO-C-H CO
? COOH COOH
NAD+ NADH+H+
CO2
α –ketoglutarate
? Oxidation of α –ketoglutarate to succinyl CoA
(catalyzed by the α –ketoglutarate dehydrogenase
complex ; the reaction requires a NAD+ )
Step 4
? Conversion of succinyl CoA to succinyl [catalyzed by
succinyl CoA synthetase; the reaction requires
inorganic phosphate and GDP(orADP)]
Step5
Succinyl-CoA
? Oxidation of succinyl to fumarate (catalyzed by succinyl
dehydrogenase; the reaction involves FAD),
Step 6
malonate
Hydration of fumarae to malate苹果酸
(catalyzed by fumarase 延胡索酸酶 )
Oxidation of malate to oxaloacetate (catalyzed by
malate dehydrogenase; the reaction requires NAD+ )
Step 8
Whole pathway
Oxaloacetate formation
? Oxidation of NADH and FADH2 produced
by the citric acid cycle
? The NADH and FADH2 produced by the
citric acid cycle are reoxidized and the
energy released is used to synthesize
ATP by oxidative phosphorylation
Energy yield
? For each turn of the cycle,10 ATP
molecules are produced,one directly
from the cycle and 9 from the re-
oxidation of the three NADH and one
FADH2 molecules produced by the
cycle oxidative phosphorylation,
Regulation
? The citric acid cycle is regulated at the
steps catalyzed by citrate synthase,
isocitrare dehydrogenase and α–
keoglutarate dehydrogenase via feedback
inhibition by ATP,citrate,NADH and
succinyl CoA,and stimulation of isocitrare
dehydrogenade by ADP,
Pyruvate dehydrogenase
? Pyruvate dehydrogenase is inhibited
by acetyl CoA and NADH,In addition,
this enzyme is inactivated by
phosphorylation,a reaction catalyzed
by pyruvate dehydrogenase kinase,
Pyruvate dehydrogenase
? A high ratio of NADH/ NAD+,acetyl
CoA/CoA or ATP/ADP stimulates ph-
osphorylation of pyruvate dehydro-
genase and so inactivates this enzyme,
Pyruvate inhibits the kinase,Removal
of the phosphate group (dephospho-
rylation) by a phosphatase reactivates
pyrucate dehydrogenase,
mode
Biosynthetic pathways
? Amino acids,purines 嘌呤 and
pyrimidines 嘧啶,porphyrins 卟啉,
fatty acids and glucose are all
synthesized by pathways that use
citric acid intermediates 中间体 as
precursors,
1,Overview
2,Redox potential
3,Electron transport from NADH
4,Formation of H+ gradient
5,Electron transport from FADH2
6,Electron transport inhibitors
Electron transport and Oxidative
phosphorylation
Overview
7,Oxidative phosphorylation
8,ATP synthase as a rotatory engine
9,Coupling and respiratory control
10,Uncouplers
11,Reoxidation of cytosolic NADH
Overview
Electron transport and oxidative
phosphorylation re-oxidize NADH and
FADH2 and trap the energy released as
ATP,In eukaryotes,electron transport
and oxidative phosphorylation occur in
the inner membrane of mitochondria
whereas in prokaryotes the process
occurs in the plasma membrane,
mode
Redox potential
? The oxidation-reduction potential,E,
(or redox potential) is a measure of
the affinity of a substance for
electrons and is measured relative to
hydrogen,
Redox potential
? Oxidation-reduced reactions involve
the transfer of electrons,In the
oxidation-reduction reactions,
? NADH+H++1/2O2 = NAD++H2O
Oxidation form
redox potential
? For biological systems,the standard
redox potential for a substance (E0') is
measured under standard conditions,
at pH7,and is expressed in volts,
? The standard free energy change of a
reaction at pH7,ΔG0‘,can be readily
calculated from the change in redox
potential E0' of the substrates and
products,
? ΔG0'＝－ nFΔE0'
redox potential
? NADH+H++1/2O2 NAD++H2O
? ΔE0' = + 1.14V
? ΔG0' = - nFΔE0 '
? ΔG0' = - 52.6 kcal mol-1
Electron transport from NADH
? NADH + H++1/2O2 NAD++H2O
? ΔG0 ' = - 52.6kcal mol-1
? And the synthesis of ATP
? ADP + PI + H+ ATP + H2O
? ΔG0 ' = +7.3kcal mol-1
overview
structure
constitute
ATP
NAD
FAD
FeS protein
Chain
UQ
Cytochrome
Oxidation
complexIII and IV
Electron transport 1
Electron transport 2
Electron transport
from FADH2
Electron transport inhibitors
? Rotenone 鱼 藤 酮 and amytal 阿密妥
inhibit electron transport at NADH
dehydrogen-ase,antimycin 抗霉素 A
inhibits the cyto-chrome bc1
complex,and cyanide 氰化物 (CN- ),azide
叠氮物 (N-3 ) and carbon monoxide(CO) all
inhibit cytochrome oxidase,
chain
Formation of an H+ gradient
? The change in redox potential along the chain is
a measure of the free energy change at each step,
At the steps involving NADH dehydrogenase,the
cytochrome bc1 complex and cytochrome
oxidase,the free energy change is large enough
to pump H+ ions across the inner mitochondrial
membrane,from the mitochondrial matrix into the
intermembrane space,to create an H+
gradient.Therefore,each of these complexes is
an H+ pump driven by electron transport,
The Chemiosmotic Theory
Peter Mitchell
proposed in
1961,
PROTON PUMP
The principal features
? (1)As electrons pass through the electron
transport chain,protons are transported
from the matrix and released into the
intermembrane space,As a result,an
electrical potential ψ and a proton
gradient ΔpH arise across the inner
membrane---the electrochemical proton
gradient,
Redox potential
? (2).Protons,which are present in the
intermembrane space in great excess,can
pass through the inner membrane and
back into the matrix down their
concentration gradient only through
special channels,As protons pass
through a channel,each of which contains
an ATP synthase activity,ATP synthesis
occurs,
Fig
Oxidative Phosphorylation
(1) Conception
The process whereby the energy
generated by the electron transport
chain is conserved by the
phosphorylation of ADP to yield ATP,
Process of Oxidative Phosphorylation
? I,The Chemical Coupling Hypothesis
? Key point,A high-energy intermediate
generated by the electron transport process
is used in a second reaction to drive the
formation of ATP from ADP and Pi,
Process
? Pi–O–CH2–CHOH–CHO + Pi
? Pi–O–CH2–CHOH–COO~Pi + ADP
? Pi–O–CH2–CHOH–COOH + ATP
Failed points
? The proposed intermediate has never
been identified,
? The hypothesis could not account for
several experimental findings,such as
uncoupler,entire inner mitochondrial
membrane,
Evidence supporting the Chemiosmotic
Theory
uncoupler,such as 2,4,-dinitrophenol
Ionophores,e.g,valinomycin and
thermogenin
FIG 1
Experiment 2
ATP synthase as a rotatory engine
? In 1964,Paul Boyer proposed the
conformational coupling hypothesis,
structure
Experiment 3
FoF1
? In 1970s,Paul Boyer has suggested
a Binding-change Mechanism on
the basis of detailed kinetic and
binding studies of the reactions
catalyzed by FoF1,
The principal features
? (1)The energy-requiring step is the
release of ATP from the enzyme (ATP
synthase) and binding of ADP and Pi,
? (2)The enzyme has three equivalent
adenine nucleotide binding sites.The
proton-motive force causes a
cooperative conformational change
during ATP synthesis,
Three conformation
? Three conformation
? L (loose-binding)
? ADP+Pi bind loosely to
? L site
? T (tight-binding)
? ATP occupies T site
? O (open)
? ATP dissociates from it
History
? In 1990s,Paul Boyer
complemented the mechanism
with rotational catalysis,
FIG
ATP synthase
? ATP synthase behaves as a rotating
molecular machine,
? The rotor (or revolving) component of the
machine consists of subunits ε,γ,and c12,
whereas subunits a,b2,δ,α3 and β3
comprise the stator (or stationary)
component,
Inhibitor of oxidative phosphorylation
? Fo is the portion of the ATP synthase and
sensitivity to oligomycin,
? Oligomycin inhibits proton passing through ATP
synthase and thus oxidative phosphorylation,
? (1) As electrons pass through the electron
transport chain,the electrochemical proton
gradient is established by proton pump across the
inner membrane of mitochondria,
? (2) Protons pass through a special channel in ATP
synthase and result in ATP synthesis by rotational
catalysis and cooperative conformational change
Coupling and respiratory control
? Electron transport is normally tightly
coupled to ATP synthesis; electrons do not
flow through the electron transport chain
to oxygen unless ADP is simultaneously
phosphorylaed to ATP,
Fig
respiratory control
? If ADP is available,electron transport
proceeds and ATP is made; as the ADP
concentration falls,electron transport slows
down,This process,called respiratory
control,ensures that electron flow occurs
only when ATP synthesis is required,
Uncouplers
? (1),uncoupling agents
? (2),Ionic carrier
? (3),Thermogenin (uncoupling protein)
DNP
ADP transport
Reoxidation of cytosolic NADH
The glycerol 3-phosphate shuttle
Malate-aspartate shuttle
1,Overview
2,Location
3,Light harvesting in green plants
4,Photosystems I and II
5,Noncyclic photophosphorylation
6,Cyclic photophosphorylation
7,Bacterial photosynthesis
8,The dark reactions
9,The C4 pathway
L3 PHOTOSYNTHESIS
Overview
? Photosynthesis 光合作用 occurs in green
plants,algae and photosynthetic bacteria,
Its role is to trap solar energy and use
this to drive the synthesis of
carbohydrate from carbon dioxide and
water,
? H2O+CO2 light (CH2O) + O2
Overview
light reactions
? Photosynthesis
dark reactions
Photosynthesis
? The light reaction,which use light energy to
synthesize NADPH and ATP;
? The dark reactions,that use the NADPH and
ATP to synthesize carbohydrate from CO2
and H2O
Photosynthesis
Location
? In green plants and algae
photosynthesis takes place in
chloroplasts,The light reactions
occur in the thylakoid类囊体
membranes and the dark reactions
take place in the stroma 基质,
Fig 2
Location
? In photosynthetic bacteria the light
reaction take place in the bacterial
plasma membrane,or in
invaginations 内陷 of it
(chromatophores 载色体 ),
Light is harvesting in green plants
Sunlight is absorbed by chlorophyll
molecules,Chlorlphyll is a porphyrin in
which nitrogen atoms are coordinated to a
magnesium ion,
Green plants contain two types of
chlorophyll molecules,chlorophyll a and
chlorophyll b,
The capture of solar energy occurs in
photosystems,Each photosystem consists
of an antenna complex and a
photosynthetic,
Light spectrum
pigment
藻红蛋白
植醇
Pigment wavelength
藻红蛋白
藻青蛋白
Light absorb
Photosystems I and II
? Green plants and algae use two types of
photosystem called photosystemI (PSI) and
photosystem II (PSII)
? Plastoquinone 质体醌
? Plastocyanin 质体蓝素
? Ferredoxin 铁氧还蛋白
PSII and PSI
Z schem
Noncyclic photophosphorylation
? The formation of ATP via the joint
operation of PSI and PSII is called
noncyclic photophosphorylation,
ATP synthesis
Compare ATP synthesis
Comparing oxidative-phosphorylation
with photophosphorylation
? Site
? Proton pump
? Energy origin
? Proton gradient
? ATP synthesis
Cyclic photophosphorylation
When little NADP+ is available to
accept electrons,cyclic
photophosphorylation is used,
Photosystem I is only pathway,
ATP is only product,
mode
Bacterial photosynthesis
? It is similar to green plants in
cyanobacteria 蓝细菌,and accessory
pigments is phycobilins 藻胆素,
? In purple photosynthetic bacteria have
only a single photosystem reaction center,
? Electron donor is hydrogen sulfide and
electron acceptor is NAD+,
The dark reaction
?The dark reactions (also called the
carbon-fixation reactions) use the ATP and
NADPH produced by the light reactions to
convert carbon dioxide into carbohydrate,
?The key carbon fixation reaction is
catalyzed by a large enzyme called
ribulose bisphosphate carboxylase 核酮糖
二磷酸羧化酶 (often abbreviated to rubisco)
Calvin cycle
Synthesis of sucrose
? UDP-glucose + fructose 6-phosphate
Sucrose 6-phosphate + UDP
? Synthesis of starch 淀粉
? ADP-glucose,CDP-glucose,
? GDP-glucose
C4 Pathway
? Since it relies on CO2 transport via
four-carbon molecules,it is called
the C4 pathway
? Photorespiration 光呼吸
? C3 plants C4 plants
? Bundle-sheath 维管束
? Mesophyll 叶肉
? Phosphoglycolate 磷酸羟乙酸
C4 pathway 2
L2,Electron transport and oxidative
hosphorylation
L3,Photosynthesis
Section L Respiration and Energy
? Role
? Location
? The cycle
? Energy yield
? Regulation
? Biosynthetic pathways
Citric acid cycle
Role
? The citric acid柠檬酸 cycle,also known as the
TCA (tricarboxylic acid三羧酸 ) cycle or Krebs
cycle (after its discover in 1993),is used to
oxidize the pyruvate formed during the glyco-
lytic breakdown of glucose into CO2 and H2O,
The cycle is a major energy source in the form
of ATP and also produces precursors for many
biosynthetic pathways,
Location
? The citric acid cycle occurs
within the mitochondria of
eukaryotes and the cytosol of
prokaryotes,
The cycle
? Step 1,Oxidation of fuel molecules to acetyl CoA
? A major source of energy is glucose which is
converted by glycolysis into pyruvate,Pyruvate
dehydrogenase (a complex of three enzymes and five
coenzymes ) then oxidizes the pyruvate (using NAD+
which is reduced to NADH ) to form acetyl CoA and
CO2 since the reaction involves both an oxidation and
a loss of CO2,the process is called oxidative
decarboxylation,
Acetyl-CoA
? The cycle carries out the oxidation
of acetyl groups from acetyl CoA to
CO2 with the production of four
pairs of electrons,stored initially in
the reduced electron carriers NADH
and FADH2
The citric acid cycle
Cycle mode
EIGHT STAGES
? The citric acid cycle has eight stages,
? (1)Production of citrate from oxaloacetate (草
酰乙酸 ) and acetyl CoA (catalyzed by citrate
synthase)
? COOH CH3 CH2-COOH
? CO + CO HO-C-COOH
? CH2 S CH2-COOH
? COOH CoA
Citrate formation
Isomerization (异构化作用 )of citrate to
isocitrate (catalyzed by aconitase 顺乌头酸酶 )
? CH2-COOH CH2-COOH
? HO-C-COOH H-C-COOH
? CH2-COOH HO-CH-COOH
Isocitrate formation
Oxidation of isocitrate to α –ketoglutarate（ α-酮
戊二酸,catalyzed by isocitrate dehydrogenase;
the reaction requires NAD+ ）
? COOH COOH
? CH2 CH2
? H-C-COOH CH2
? HO-C-H CO
? COOH COOH
NAD+ NADH+H+
CO2
α –ketoglutarate
? Oxidation of α –ketoglutarate to succinyl CoA
(catalyzed by the α –ketoglutarate dehydrogenase
complex ; the reaction requires a NAD+ )
Step 4
? Conversion of succinyl CoA to succinyl [catalyzed by
succinyl CoA synthetase; the reaction requires
inorganic phosphate and GDP(orADP)]
Step5
Succinyl-CoA
? Oxidation of succinyl to fumarate (catalyzed by succinyl
dehydrogenase; the reaction involves FAD),
Step 6
malonate
Hydration of fumarae to malate苹果酸
(catalyzed by fumarase 延胡索酸酶 )
Oxidation of malate to oxaloacetate (catalyzed by
malate dehydrogenase; the reaction requires NAD+ )
Step 8
Whole pathway
Oxaloacetate formation
? Oxidation of NADH and FADH2 produced
by the citric acid cycle
? The NADH and FADH2 produced by the
citric acid cycle are reoxidized and the
energy released is used to synthesize
ATP by oxidative phosphorylation
Energy yield
? For each turn of the cycle,10 ATP
molecules are produced,one directly
from the cycle and 9 from the re-
oxidation of the three NADH and one
FADH2 molecules produced by the
cycle oxidative phosphorylation,
Regulation
? The citric acid cycle is regulated at the
steps catalyzed by citrate synthase,
isocitrare dehydrogenase and α–
keoglutarate dehydrogenase via feedback
inhibition by ATP,citrate,NADH and
succinyl CoA,and stimulation of isocitrare
dehydrogenade by ADP,
Pyruvate dehydrogenase
? Pyruvate dehydrogenase is inhibited
by acetyl CoA and NADH,In addition,
this enzyme is inactivated by
phosphorylation,a reaction catalyzed
by pyruvate dehydrogenase kinase,
Pyruvate dehydrogenase
? A high ratio of NADH/ NAD+,acetyl
CoA/CoA or ATP/ADP stimulates ph-
osphorylation of pyruvate dehydro-
genase and so inactivates this enzyme,
Pyruvate inhibits the kinase,Removal
of the phosphate group (dephospho-
rylation) by a phosphatase reactivates
pyrucate dehydrogenase,
mode
Biosynthetic pathways
? Amino acids,purines 嘌呤 and
pyrimidines 嘧啶,porphyrins 卟啉,
fatty acids and glucose are all
synthesized by pathways that use
citric acid intermediates 中间体 as
precursors,
1,Overview
2,Redox potential
3,Electron transport from NADH
4,Formation of H+ gradient
5,Electron transport from FADH2
6,Electron transport inhibitors
Electron transport and Oxidative
phosphorylation
Overview
7,Oxidative phosphorylation
8,ATP synthase as a rotatory engine
9,Coupling and respiratory control
10,Uncouplers
11,Reoxidation of cytosolic NADH
Overview
Electron transport and oxidative
phosphorylation re-oxidize NADH and
FADH2 and trap the energy released as
ATP,In eukaryotes,electron transport
and oxidative phosphorylation occur in
the inner membrane of mitochondria
whereas in prokaryotes the process
occurs in the plasma membrane,
mode
Redox potential
? The oxidation-reduction potential,E,
(or redox potential) is a measure of
the affinity of a substance for
electrons and is measured relative to
hydrogen,
Redox potential
? Oxidation-reduced reactions involve
the transfer of electrons,In the
oxidation-reduction reactions,
? NADH+H++1/2O2 = NAD++H2O
Oxidation form
redox potential
? For biological systems,the standard
redox potential for a substance (E0') is
measured under standard conditions,
at pH7,and is expressed in volts,
? The standard free energy change of a
reaction at pH7,ΔG0‘,can be readily
calculated from the change in redox
potential E0' of the substrates and
products,
? ΔG0'＝－ nFΔE0'
redox potential
? NADH+H++1/2O2 NAD++H2O
? ΔE0' = + 1.14V
? ΔG0' = - nFΔE0 '
? ΔG0' = - 52.6 kcal mol-1
Electron transport from NADH
? NADH + H++1/2O2 NAD++H2O
? ΔG0 ' = - 52.6kcal mol-1
? And the synthesis of ATP
? ADP + PI + H+ ATP + H2O
? ΔG0 ' = +7.3kcal mol-1
overview
structure
constitute
ATP
NAD
FAD
FeS protein
Chain
UQ
Cytochrome
Oxidation
complexIII and IV
Electron transport 1
Electron transport 2
Electron transport
from FADH2
Electron transport inhibitors
? Rotenone 鱼 藤 酮 and amytal 阿密妥
inhibit electron transport at NADH
dehydrogen-ase,antimycin 抗霉素 A
inhibits the cyto-chrome bc1
complex,and cyanide 氰化物 (CN- ),azide
叠氮物 (N-3 ) and carbon monoxide(CO) all
inhibit cytochrome oxidase,
chain
Formation of an H+ gradient
? The change in redox potential along the chain is
a measure of the free energy change at each step,
At the steps involving NADH dehydrogenase,the
cytochrome bc1 complex and cytochrome
oxidase,the free energy change is large enough
to pump H+ ions across the inner mitochondrial
membrane,from the mitochondrial matrix into the
intermembrane space,to create an H+
gradient.Therefore,each of these complexes is
an H+ pump driven by electron transport,
The Chemiosmotic Theory
Peter Mitchell
proposed in
1961,
PROTON PUMP
The principal features
? (1)As electrons pass through the electron
transport chain,protons are transported
from the matrix and released into the
intermembrane space,As a result,an
electrical potential ψ and a proton
gradient ΔpH arise across the inner
membrane---the electrochemical proton
gradient,
Redox potential
? (2).Protons,which are present in the
intermembrane space in great excess,can
pass through the inner membrane and
back into the matrix down their
concentration gradient only through
special channels,As protons pass
through a channel,each of which contains
an ATP synthase activity,ATP synthesis
occurs,
Fig
Oxidative Phosphorylation
(1) Conception
The process whereby the energy
generated by the electron transport
chain is conserved by the
phosphorylation of ADP to yield ATP,
Process of Oxidative Phosphorylation
? I,The Chemical Coupling Hypothesis
? Key point,A high-energy intermediate
generated by the electron transport process
is used in a second reaction to drive the
formation of ATP from ADP and Pi,
Process
? Pi–O–CH2–CHOH–CHO + Pi
? Pi–O–CH2–CHOH–COO~Pi + ADP
? Pi–O–CH2–CHOH–COOH + ATP
Failed points
? The proposed intermediate has never
been identified,
? The hypothesis could not account for
several experimental findings,such as
uncoupler,entire inner mitochondrial
membrane,
Evidence supporting the Chemiosmotic
Theory
uncoupler,such as 2,4,-dinitrophenol
Ionophores,e.g,valinomycin and
thermogenin
FIG 1
Experiment 2
ATP synthase as a rotatory engine
? In 1964,Paul Boyer proposed the
conformational coupling hypothesis,
structure
Experiment 3
FoF1
? In 1970s,Paul Boyer has suggested
a Binding-change Mechanism on
the basis of detailed kinetic and
binding studies of the reactions
catalyzed by FoF1,
The principal features
? (1)The energy-requiring step is the
release of ATP from the enzyme (ATP
synthase) and binding of ADP and Pi,
? (2)The enzyme has three equivalent
adenine nucleotide binding sites.The
proton-motive force causes a
cooperative conformational change
during ATP synthesis,
Three conformation
? Three conformation
? L (loose-binding)
? ADP+Pi bind loosely to
? L site
? T (tight-binding)
? ATP occupies T site
? O (open)
? ATP dissociates from it
History
? In 1990s,Paul Boyer
complemented the mechanism
with rotational catalysis,
FIG
ATP synthase
? ATP synthase behaves as a rotating
molecular machine,
? The rotor (or revolving) component of the
machine consists of subunits ε,γ,and c12,
whereas subunits a,b2,δ,α3 and β3
comprise the stator (or stationary)
component,
Inhibitor of oxidative phosphorylation
? Fo is the portion of the ATP synthase and
sensitivity to oligomycin,
? Oligomycin inhibits proton passing through ATP
synthase and thus oxidative phosphorylation,
? (1) As electrons pass through the electron
transport chain,the electrochemical proton
gradient is established by proton pump across the
inner membrane of mitochondria,
? (2) Protons pass through a special channel in ATP
synthase and result in ATP synthesis by rotational
catalysis and cooperative conformational change
Coupling and respiratory control
? Electron transport is normally tightly
coupled to ATP synthesis; electrons do not
flow through the electron transport chain
to oxygen unless ADP is simultaneously
phosphorylaed to ATP,
Fig
respiratory control
? If ADP is available,electron transport
proceeds and ATP is made; as the ADP
concentration falls,electron transport slows
down,This process,called respiratory
control,ensures that electron flow occurs
only when ATP synthesis is required,
Uncouplers
? (1),uncoupling agents
? (2),Ionic carrier
? (3),Thermogenin (uncoupling protein)
DNP
ADP transport
Reoxidation of cytosolic NADH
The glycerol 3-phosphate shuttle
Malate-aspartate shuttle
1,Overview
2,Location
3,Light harvesting in green plants
4,Photosystems I and II
5,Noncyclic photophosphorylation
6,Cyclic photophosphorylation
7,Bacterial photosynthesis
8,The dark reactions
9,The C4 pathway
L3 PHOTOSYNTHESIS
Overview
? Photosynthesis 光合作用 occurs in green
plants,algae and photosynthetic bacteria,
Its role is to trap solar energy and use
this to drive the synthesis of
carbohydrate from carbon dioxide and
water,
? H2O+CO2 light (CH2O) + O2
Overview
light reactions
? Photosynthesis
dark reactions
Photosynthesis
? The light reaction,which use light energy to
synthesize NADPH and ATP;
? The dark reactions,that use the NADPH and
ATP to synthesize carbohydrate from CO2
and H2O
Photosynthesis
Location
? In green plants and algae
photosynthesis takes place in
chloroplasts,The light reactions
occur in the thylakoid类囊体
membranes and the dark reactions
take place in the stroma 基质,
Fig 2
Location
? In photosynthetic bacteria the light
reaction take place in the bacterial
plasma membrane,or in
invaginations 内陷 of it
(chromatophores 载色体 ),
Light is harvesting in green plants
Sunlight is absorbed by chlorophyll
molecules,Chlorlphyll is a porphyrin in
which nitrogen atoms are coordinated to a
magnesium ion,
Green plants contain two types of
chlorophyll molecules,chlorophyll a and
chlorophyll b,
The capture of solar energy occurs in
photosystems,Each photosystem consists
of an antenna complex and a
photosynthetic,
Light spectrum
pigment
藻红蛋白
植醇
Pigment wavelength
藻红蛋白
藻青蛋白
Light absorb
Photosystems I and II
? Green plants and algae use two types of
photosystem called photosystemI (PSI) and
photosystem II (PSII)
? Plastoquinone 质体醌
? Plastocyanin 质体蓝素
? Ferredoxin 铁氧还蛋白
PSII and PSI
Z schem
Noncyclic photophosphorylation
? The formation of ATP via the joint
operation of PSI and PSII is called
noncyclic photophosphorylation,
ATP synthesis
Compare ATP synthesis
Comparing oxidative-phosphorylation
with photophosphorylation
? Site
? Proton pump
? Energy origin
? Proton gradient
? ATP synthesis
Cyclic photophosphorylation
When little NADP+ is available to
accept electrons,cyclic
photophosphorylation is used,
Photosystem I is only pathway,
ATP is only product,
mode
Bacterial photosynthesis
? It is similar to green plants in
cyanobacteria 蓝细菌,and accessory
pigments is phycobilins 藻胆素,
? In purple photosynthetic bacteria have
only a single photosystem reaction center,
? Electron donor is hydrogen sulfide and
electron acceptor is NAD+,
The dark reaction
?The dark reactions (also called the
carbon-fixation reactions) use the ATP and
NADPH produced by the light reactions to
convert carbon dioxide into carbohydrate,
?The key carbon fixation reaction is
catalyzed by a large enzyme called
ribulose bisphosphate carboxylase 核酮糖
二磷酸羧化酶 (often abbreviated to rubisco)
Calvin cycle
Synthesis of sucrose
? UDP-glucose + fructose 6-phosphate
Sucrose 6-phosphate + UDP
? Synthesis of starch 淀粉
? ADP-glucose,CDP-glucose,
? GDP-glucose
C4 Pathway
? Since it relies on CO2 transport via
four-carbon molecules,it is called
the C4 pathway
? Photorespiration 光呼吸
? C3 plants C4 plants
? Bundle-sheath 维管束
? Mesophyll 叶肉
? Phosphoglycolate 磷酸羟乙酸
C4 pathway 2
