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

knowmatrix

Inner membrane(cristae)

Outer membrane

Intermembrane space

14_02_Mitochon_ATP.jpgMitochondrial diversity [Fig. 14-2]

Biochemical anatomy ofMitochondria [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 phosphor-ylation

14_04_NADH_electron.jpgNADH kickstarts electron transport chain in mitochondria

14_07_Mito_catalyze.jpgChemiosmotic theory (Paul Mitchell, 1960’s):

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 inter-membrane 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 makesmembrane permeable to H+

Chemiosmotic coupling: Experimental evidence

14_10_resp_enzy_comp.jpgElectron transport and H+ pumping in mitochondria

Lehninger Principles of Biochemistry

14_12_deltaV_deltapH.jpg

Electrochemical gradient (ΔμH+) = ΔV or ΔE + ΔpH

14_13_electroch_gradie.jpgOxidative phosphorylation [Fig. 14-13]

14_21_Redox_potential .jpg

Electrons flow from –ve to +ve redox potential carriers

Lehninger Principles of Biochemistry

Lehninger Principles of Biochemistry

14_24_Cytochrome_ox.jpg

Cytochrome oxidase: e- transport, O2 reduction and H+ pumping

O2 O2- OH. H2O2

Superoxide Hydroxyl free radical free radical

FO-F1 ATP synthase complex: Uses proton electrochemical gradient to make ATP [Fig. 14-14]

14_15_ATPsynthase2.jpgATP synthase/ ATPase: a reversible enzyme [Fig. 14-15]

ATP synthase/ATPase: World’s smallest rotary motor:Experimental evidence

Video pictures of rotation of the γ-subunit of ATP synthase

14_16_coupled_transpor.jpg

Transport across inner mitochondrial membrane

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]

14_30_3rd_compartmnt.jpg

Three membranes in chloroplast: the outer, the inner and thylakoid membranes

14_31_mito_chloroplas.jpg

Mitochondria vs. Chloroplasts

14_32_photsyn_react.jpg

Light and dark reactionsof photosynthesis occurin chloroplasts

14_33_Chlorophyll.jpg

Chlorophyll molecule

14_34_photosystem.jpg

A photosystem = a reaction center + an antenna

14_36_thylakoid_memb.jpg Electron transport and H+ pumping in chloroplast

Proton and electron circuitsIn thylakoids [Lehninger]

Photophosphorylation and NADP reduction [Fig. 14-37]

14_39_Carb_fix_cycle.jpg

The carbon fixation cycleor Calvin cycle Rubisco enzyme

-40% of total leaf soluble protein-Conc. In stroma: 4 mM

1. Carboxylation

2. Reduction

3. Regeneration

Fig. 1-21: origin of chloroplasts.

Early eukaryote

cyanobacterium

Early eukaryotic cell capable of photosynthesis

chloroplasts

Fig. 13-39: Phylogenetic tree based on rDNA sequences (Fig. 9-15, new book)

Mitochondrial genes are

shown in red. chloroplasts genes are

shown in green.

What organisms are mitochondrial or chloroplast genes most closely related to?