BIOL 200 (Section 921)
Lecture # 8 (Unit 6)
June 28, 2006
UNIT 6: MITOCHONDRIA AND
CHLOROPLASTS
Reading:
• ECB 2nd ed. Chap 14, pp. 453-492 and related
questions, especially 14-3; 14-11B,C,E, H;14-13;
14-16.
• ECB 1st ed. Chap 13, pp. 407-442 and related
questions, especially 13-3; 13-11B,C,E, H;13-13;
13-17.
Learning objectives
1. Application of chemiosmotic theory to
understand the structure-function
relationships of the mitochondrial energy
transduction system.
2. Understand the role of electron transport
complexes in the establishment of
mitochondrial proton gradient
Unit 6: Mitochondria and chloroplasts [Chapter 14]
1
2
3
4
Fig. 14-3
Fig. 14-3: Mitochondrial
structures that you should
know
matrix
Inner membrane(cristae)
Outer
membrane
Intermembrane space
Mitochondrial diversity [Fig. 14-2]
14_02_Mitochon_ATP.jpg
Biochemical anatomy of
Mitochondria [Lehninger]
Fig. 13-2:
reduced carbon
compounds are
the fuel for the
mitochondria
When they get
“burned” or
oxidized, CO2 is
released.
Food in
Glycolysis in
cytoplasm
Citric acid
cycle in
matrix of
mitochondrion
Oxidative
phosphorylation
NADH kickstarts electron transport chain in mitochondria
14_04_NADH_electron.jpg
Chemiosmotic theory (Paul Mitchell, 1960’s):
14_07_Mito_catalyze.jpg
Coupling of electron transfer, proton pumping and ATP synthesis
14_05_generate_energy.jpg
Chemiosmotic process
Fig. 14-1: Mitchell’s chemiosmotic hypothesis
1. Electron transport
causes protons to be
exported to the intermembrane space.
2. Proton gradient is
harnessed by ATP
synthase to make ATP.
14_08_Uncoupl_agents.jpg
Uncouplers (e.g. DNP),
are H+ carriers and makes
membrane permeable to H+
Chemiosmotic coupling: Experimental evidence
Electron transport and H+ pumping in mitochondria
14_10_resp_enzy_comp.jpg
Lehninger Principles of Biochemistry
Electrochemical gradient (ΔμH+) = ΔV or ΔE + ΔpH
14_12_deltaV_deltapH.jpg
Oxidative phosphorylation [Fig. 14-13]
14_13_electroch_gradie.jpg
Electrons flow from –ve to +ve redox potential carriers
14_21_Redox_potential .jpg
Lehninger Principles of Biochemistry
Lehninger Principles of Biochemistry
Cytochrome oxidase: e- transport, O2 reduction and H+ pumping
14_24_Cytochrome_ox.jpg
O2 
O 2-

Superoxide
free radical
OH.
 H2O2
Hydroxyl
free radical
FO-F1 ATP synthase complex: Uses proton
electrochemical gradient to make ATP [Fig. 14-14]
ATP synthase/ ATPase: a reversible enzyme [Fig. 14-15]
14_15_ATPsynthase2.jpg
ATP synthase/ATPase: World’s smallest rotary motor:
Experimental evidence
Video pictures of rotation of the
γ-subunit of ATP synthase
Transport across inner mitochondrial membrane
14_16_coupled_transpor.jpg
Learning objectives
1. Application of chemiosmotic theory to
understand the structure-function
relationships of the chloroplast energy
transduction system.
2. Understand the role of electron transport
complexes in the establishment of
chloroplast proton gradient
Plastids are specialized for different functions.
• Chloroplasts are green plastids specialized for photosynthesis.
• Chromoplasts are plastids filled with orange or yellow
pigments that give colour to flowers and fruit.
• Amyloplasts are plastids that store starch in storage tissues
such as seeds, roots and stems. Amyloplasts in the root cap fall
to one side of a cell and signal gravity perception
• Etioplasts are plastids which develop in tissues in the dark and
lack pigments.
• Proplastids are a juvenile form of plastid that occurs in
embryos and apical meristems. They give rise to all other types
of plastids depending on requirements of each differentiated
plant cell.
Photosynthesis occurs in chloroplasts [Fig. 14-29]
Three membranes in chloroplast: the outer, the inner and thylakoid membranes
14_30_3rd_compartmnt.jpg
Mitochondria vs. Chloroplasts
14_31_mito_chloroplas.jpg
Light and dark reactions
of photosynthesis occur
in chloroplasts
14_32_photsyn_react.jpg
14_33_Chlorophyll.jpg
Chlorophyll molecule
A photosystem = a reaction center + an antenna
14_34_photosystem.jpg
Electron transport and H+ pumping in chloroplast
14_36_thylakoid_memb.jpg
Proton and electron circuits
In thylakoids [Lehninger]
Photophosphorylation and NADP reduction [Fig. 14-37]
The carbon fixation cycle
or Calvin cycle
1. Carboxylation
Rubisco enzyme
14_39_Carb_fix_cycle.jpg
-40% of total leaf soluble protein
-Conc. In stroma: 4 mM
3. Regeneration
2. Reduction
Fig. 1-21: origin of chloroplasts.
Early eukaryote
Early eukaryotic cell
capable of
photosynthesis
chloroplasts
cyanobacterium
Fig. 13-39: Phylogenetic tree based on rDNA
sequences (Fig. 9-15, new book)
What organisms are mitochondrial or
chloroplast genes most closely related to?
Mitochondrial
genes are
shown in red.
chloroplasts
genes are
shown in green.