1. Lecture 12 Energy Conversion: Mitochondria and Chloroplasts

2. 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

3. Chemiosmotic coupling

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

5. Mitochondria move along MT
Mitochondrial plasticity

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

7. 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

8. Oxidative phosphorylation
ATP synthase
Respiratory enzyme complexes

9. 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

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

11. 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!

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

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

15. 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

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

17. A dividing mito

18. Various sizes of mitochondrial genomes
Nucleoids: similar to bacterial DNA
circular
,000 nt

19. Suggested evolutionary
pathway for the origin
of mitochondria

20. 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

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

22. 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

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

24. 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