Lecture 12 Energy Conversion: Mitochondria and Chloroplasts

Chemiosmotic coupling: the common pathway used by mito, chloroplasts and procaryotes ATP (chemi) Membrane transport (osmotic) Large amount of internal membrane in mitochondria and chloroplasts

Chemiosmotic coupling

Electron transport processes High-energy Low-energy Photosystems: drive electrons in opposite directions Electron transport chain

Mitochondria move along MT Mitochondrial plasticity

MT wind along axoneme in development and then disappears and mito fuse… Fixed in position

Biochemical fractionation of purified mito Study different proteins in each compartment Process large numbers of mito at the same time Low osmotic strength Cristae of the inner membrane unfold Outer membrane (no folds) break

Oxidative phosphorylation ATP synthase Respiratory enzyme complexes

F0F1 ATPase, 500 kd F1 Lollipop head Proton causes rotation and rubbing Of two sets of proteins against each Other: rotating stalk proteins and Head proteins F0F1 ATPase, 500 kd F1 Lollipop head >100 ATPs Per minute

Reversible coupling device ATP synthase can also function in reverse to hydrolyze ATP and pump H+ Reversible coupling device

Plastids A proplastid from a root tip cell of a bean plant Three amyloplasts (leucoplasts) or starch- Storing palstids in a root tip cell of soybean Purine and pyrimidine synthesis, aa synthesis FA synthesis All take place in plastids!

Inner membrane is not folded Electron transport chains, photosystems, ATP synthase are present in thylakoid membrane

ATP synthase protrudes from into the matrix from the inner mitochondrial membrane ATP synthase Protrudes From the thylakoid Membrane into The stroma

Carbon fixation reactions (dark reactions): Photosynthesis Photosynthestic electron transfer reactions (light reactions): Chlorophyll engergizes an electron using Light energy Electron comes from H2O and O2 is a by-product ATP synthesis and NADPH Carbon fixation reactions (dark reactions): Ribulose bisphosphate carboxylase

The antenna complex and photochemical reaction center in a photosystem “Funnel”

A dividing mito

Various sizes of mitochondrial genomes Nucleoids: similar to bacterial DNA circular 6000-300,000 nt

Suggested evolutionary pathway for the origin of mitochondria

Human mitochondria genome: 16,569 nt. Sequenced in 1981. Dense gene packing--not much regulatory sequences Relaxed codon usage--only 22 tRNA (30 in cytosol), many tRNAs recognize any one of the four Nt in the third (wobble) position 3. Variant genetic code-- 4 of the 64 codons have different meanings

More than 20 chloroplast genomes have been sequenced Similarity to bacteria is striking

In higher animals, the progeny contain only maternal mito. In 2/3 higher plants, chloroplasts are also maternally inherited In other plants, pollen chloroplasts enter the zygote-biparental-variegation

Mitochondria import lipids Chloroplasts make their own Mito converts imported lipids To cardiolipin (inner membrane)

Summary Chemiosmotic coupling and electron transport Mitochondria are plastic and can be motile Oxidative phosphorylation and ATP synthase Plastids and chloroplasts Photosynthesis, antenna and reaction center Mitochondrial and chloroplast genomes Inheritance of organelle genomes and biosynthesis