Download Energy Generation in Mitochondria and Chloroplasts

Chapter 6
Energy Generation in
Mitochondria and Chloroplasts
(1) Mitochondria: in all eukaryotic cells
The relationship between the structure and function of mit.
(2) Chloroplasts: in plant cells
The relationship between the structure and function of chl.
Mit: Oxidative phosphorylation→ ATP
Chl: Photosynthesis→ ATP+NADPH→ Sugar
1. Mitochondria and oxidative phosphorylation
A. Mitochondrial structure and function
™The size and number of mitochondria reflect
the energy requirements of the cell.
™Inner and outer mitochondrial membranes enclose
two spaces: the matrix and intermembrane space.
Outer membrane:
Contains channel-forming protein, called Porin.
Permeable to all molecules of 5000 daltons or less.
Inner membrane (Impermeability):
Contains proteins with three types of functions:
(1) Electron-transport chain: Carry out oxidation reactions;
(2) ATP synthase: Makes ATP in the matrix;
(3) Transport proteins: Allow the passage of metabolites
Intermembrane space:
Contains several enzymes use ATP to phosphorylate
other nucleotides.
Matrix: Enzymes; Mit DNA, Ribosomes, etc.
B. Specific functions localized within the Mit by
disruption of the organelle and fractionation
Localization of metabolic functions within the mitochondrion
Outer membrane:
Phospholipid synthesis
fatty acid desaturation
Fatty acid elongation
Inner membrane:
Electron transport
Oxidative phosphorylation
Metabolite transport
Marker:monoamine oxidase Cardiolipin/TPL(20%)
Marker:cytochrome oxidase
Matrix：
Pyruvate oxidation
Intermembrane space
TCA cycle
Nucleotide phosphorylation
ß oxidation of fats
Marker: adenylate kinase
DNA replication, RNA transcription,
Protein translation
Marker: MDH
2. Molecular basis of oxidative
phosphorylation
A. Molecular basis of oxidation: Electrontransport chain
B. Molecular basis of phosphorylation:
ATP synthase
™ The structure of the ATP synthase
F1 particle is the catalytic subunit;
The F0 particle attaches to F1 and is
embedded in the inner membrane.
F1: 5 subunits in
the ratio
3α:3β:1γ:1δ:1ε
F0: 1a：2b：12c
™F1 particles have ATP synthase activity
™ Proton translocation through F0 drives ATP synthesis
by F1: Binding Change Model and rotational catalysis
Boyer proposed in
1979, and was
greatly stimulated
by the publication
in 1994 of the
structure for F1
complex (X-ray)
from bovine heart
mitochondria
™Direct experimental evidence supporting the
rotational catalysis.
Japan researcher,
Nature 386: 300,
1997.
™ The ATP synthase is a reversible coupling device
™ Other roles for the proton-motive force in
addition to ATP synthase
Regulate for Ca2+
C. Mithchell’s Chemiosmotic theory (1961)
™The pH and electrical gradient resulting from
transport of protons links oxidation to phosphorylation.
™When electrons are passed to carriers only able to
accept electrons, the H+ is translocated across the inner
membrane.
More than 2¯1026 molecules (>160kg) of ATP per day in our bodies.
Electrons pass from NADH or FADH2 to O2, the terminal
electron acceptor, through a chain of carriers in the inner
membrane (FMN, Fe-S center, Heme group Fe, CoQ);
As electrons move through the electron-transport chain, H+ are
pumped out across the inner membrane, and form Proton
motive force;
Electrons move through the inner membrane via a series of
carriers of decreasing redox potential
A testable prediction followed
from Mitchell’s hypothesis
If not all the
detergent is
removed,
what will
happen?
™Summary of the major activities during aerobic
respiration in a mitochondrion
NADH€O2: 3ATP/2e;
FADH2 €O2 : 2ATP/2e
Ø生物氧化产生ATP的统计：
一个葡萄糖分子经过细胞呼吸全过程产生多少ATP？
糖酵解：底物水平磷酸化产生 4 ATP（细胞质）
己糖分子活化消耗 2 ATP（细胞质）
产生 2NADH，经电子传递产生 3或 5 ATP
（线粒体）净积累 5 或 7 ATP
丙酮酸氧化脱羧：产生 2NADH（线粒体），生成 5 ATP
三羧酸循环：底物水平的磷酸化产生（线粒体）2 ATP；
产生 6NADH（线粒体），生成 15 ATP；
产生 2FADH2（线粒体），生成 3 ATP。
总计生成
30 或 32 ATP
3. Chloroplast and photosynthesis
A. The structure of Chloroplasts
B. Photosynthesis
C. The antenna complex and photochemical reaction
center in a photosystem
Light-dependent reaction: Electron transport in the
thylakoid membrane and noncyclic
photophosphorylation:
Cyclic photophosphorylation:
Changes in redox potential during photosynthesis.
™Carbon dioxide fixation and the synthesis of
carbohydrate in C3 plants (Calvin cycle)
The structure and function in C4 plants
CAM plants: CO2被2次固定，但只
需1种细胞（Mesophyll cell） crassulacean acid metabolism景天植物酸代谢
4. Organelle DNA and protein importing
A. Organelle DNA
™The size range of organelle DNA is similar to that of viral DNAs.
¾Mit DNA: from <6000bp (plasmodium falciparum) ～ >300000bp (some land
plants). DNA of Mit genome(in mammals) ≈16500bp(<0.001% of nuclear
genome) ; Chl genomes are about 10 times larger and contain about 120 genes.
¾Chl DNA: from 70000 to 200000bp (genome of land plants);
™Genes in mtDNA encode rRNAs, tRNAs, and some
mitochondrial proteins。
Human mt DNA: 16,569bp
2 rRNAs（16s and 12s RNA）, 22 tRNAs,
13 polypeptides: NADH reductase. 7 sub.
Cty b-c1 complex. 1 cytb
Cyt oxidase. 3 subunits
ATP synthase: 2 F0 sub
The organization of the liverwort(地钱) Chl genome
B. Mit and Chl have their own genetic systems
Mit and Chl are
organelles
semiautocephaly.
The synthesis of
mt proteins is
coordinated
C. The transport protein into Mit. And Chl.
™Tree proteins translocators in Mit membranes:
¾TOM, TIM,and OXA complex
are multimeric membrane protein,
that catalyze protein transport
across Mit membrane, TOM, TIM
stand for translocase of the outer
and inner Mit membranes
respectively.
¾TOM functions across the outer
membrane; TIM(TIM23 and
TIM22) function across the inner
membrane.
¾OXA mediates the insertion of
inner membrane proteins that are
synthesized within the Mit. OXA
also helps TOM and TIM to insert
some proteins into the matrix.
™Translocation of precursors to the matrix occurs at
the sites where the outer and inner membranes are
close together;
™The protein import by Mit:
N-terminal signal sequence is recognized by receptors of TOM;
The protein is translocated across both Mit membranes at or near
special contact sites.
™Only unfolded proteins can be imported into Mit;
¾Mit precursor proteins remain unfolded through interactions
with hsp70 chaperone proteins in the cytosol after they are
synthesized.
™ATP hydrolysis and H+ gradient are used to dtive
protein import into Mit
™Protein transport into the inner Mit membrane and
the intermembrane space requires two signal sequences
™Two signal
sequences are
required to
direct
proteins to
the Thylakoid
membrane in
Chl.
Translocation
into thylakoid
space or
thylakoid M can
occur by any
one of at least
four routes.
5. The proliferation and origin of Mit and Chl.
A. Organelle growth and division determine the
number of Mitochondria and Plastids in a cell
™Mit fission and fusion (a dividing Mit in a liver cell);
Dividing or Budding of Mit.
™Chloroplasts: dividing and formation of chloroplasts from
proplastids begins by the light-induced budding of the inner
membrane.
B. Origin: The endosymbiont theory
™Compare the ribosomal
RNA with the base sequence
of various bacterial rRNAs:
Purple bactria-Mitochondria
Cyanobacteria-Chloroplasts
Suggested evolutionary
pathway for the origin of
Mit.