1. Mitochondria and Energy Conversion
Chapter 6
Mitochondria and Energy Conversion

2. The sun is the ultimate source of energy all organisms and cells

3. ATP- “the free-energy currency”
Every day, we build bones, move muscles, think, and perform many other activities with our bodies. All of these activities are based upon energy .
ATP: The Perfect Energy Currency for the Cell ?

4. Mitochondria- the power plants of ATP
Mitochondria are double layer membrane-enclosed organelles distributed through the cytosol of most eukaryotic cells. Their main function is the conversion of the potential energy of food molecules into ATP. So mitochondria are also called “the powerhouse” of the cell.
In addition to supplying cellular energy, mitochondria are involved in cell death, as well as the control of the cell cycle and cell growth.

5. Outline of Mitochondria
Brief History of Mitochondria studies
Mitochondrial morphology and Structure
Cellular respiration and Energy Conversion
Mitochondria and cell death
Mitochondria and diseases

6. Brief History of Mitochondria studies
Richard Altmannin 1894, established them as cell organelles and called them "bioblasts".
The term "mitochondria" was coined by Carl Benda in 1898.
Leonor Michaelis discovered Janus green can be used as a supravital stain for mitochondria in 1900.
In 1913 particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called "grana".
The first high resolution micrographs appeared in 1952, replacing the Janus Green stains .
The popular term "powerhouse of the cell" was coined by Philip Siekevitz in 1957.

7. Mitochondrial Morphology and Structure
I. Shape, size & number
Mitochondria are often flexible, rod-shaped organelles that are about 0.5 to 1μm in girth and as much as 7 μ m in length. Mitochondria vary considerably in size & shape.
Their number correlate with the metabolic activities of the cell.

8. II Ultrostructure and Functional Localization
1. Outer membrane
2. Inner membrane
3. Inter membrane space
4. Translocation contact site   
 5.Matrix
6. Cristae

9. II Ultrostructure and Functional Localization

10. II Ultrostructure and Functional Localization

11. 1. Outer membrane
contains many complexes of integral membrane proteins that form channels through which a variety of molecules and ions move in and out of the mitochondrion. we called it porins. These porins form channels that allow molecules 5000 Daltons or less in molecular weight to freely diffuse from one side of the membrane to the other.

12. 2. Inner membrane
The inner membrane, which encloses the matrix space, is folded to form cristae. The area of the inner membrane is about five times as great as the outer membrane.
This membrane is richly endowed with cardiolipin, a phospholipid that possesses four, rather than the usual two, fatty acyl chains. The presence of this phospholipid in high concentration makes the inner membrane nearly impermeable to ions, electrons, and protons.
The inner membrane has a very high protein-to-phospholipid ratio (about 4:1 by weight).
Impermeable to most charged molecules

13. Inner membrane contains three major types of proteins:
① those that carry out the oxidation reactions of the respiratory chain
NADH dehydrogenase
Cytochrome b-c1
Cytochrome oxidase
② ATP synthetase
③ specific transport proteins

14. 4. Translocation contact site
3. Inter membrane space
contains several enzymes that use the ATP that passes out of the matrix to phosphorylate other nucleotides.
4. Translocation contact site
TOM(Translocon of the outer membrane)
TIM(Translocon of the inner membrane)

15. 5. Matrix
contains hundreds of different enzymes including those required for
①the oxidation of pyruvate and fatty acids
②the citric acid cycle.
It also contains small amounts of mitochordrial DNA genome, special mitochondrial ribosomes, tRNAs and various enzymes that required for the expression of the mitochondrial genes.

16. Chemical composition:
The outer membrane consists of 40% lipids and 60 percent proteins.  
The inner membrane is made up of 20% lipids and 80% proteins.  The electron transport enzymes, proton secreting proteins are virtually buried in the core of the inner membranes. 
Mitochondrial matrix also consists of a wide variety of enzymes. There are more than 120 kinds of enzymes of mitochondrial.
Mitochondrial matrix also contains DNA, RNA molecules.

17. The mitochondrial genome

18. The human mitochondrion contains 5-10 identical molecules of DNA
The human mitochondrion contains 5-10 identical molecules of DNA. Mitochondrial DNA(mtDNA) are circular, double-stranded structures of molecules in higher eukaryotes. They encode their own mRNA, rRNA and ribosomal proteins, tRNAs and a few mitochondrial proteins.
Each mitochondrion consists of 16’569 base pairs carrying the information for 37 genes.
but only 13 of these code for polypeptides, the remainder being the 2 ribosomal subunits and 22 types of transfer RNA.
However, most of the proteins in the mitochondrion are encoded in nucleus by nuclear DNA, synthesized in cytosol, and subsequently transported into the mitochondrion.

19. Because the growth and proliferation of mitochondria are controlled by both nuclear genome and it’s own genome. Mitochondria are usually called semiautonomous organelle.

20. The transport protein into Mitochondria
Mitochondrial proteins are first fully synthesized as precursor proteins in the cytosol and then translocated into mitochondria by a posttranslational mechanism.

21. 1. Translocation into the Mitochondrial Matrix Depends on a Signal Sequence and Protein Translocators

22. 2. Mitochondrial Precursor Proteins Are Imported as Unfolded Polypeptide Chains.
Mitochondrial precursor proteins do not fold into their native structures after they are synthesized; instead, they remain unfolded through interactions with other proteins in the cytosol(hsp70).

23. 3. Mitochondrial Proteins Are Imported into the Matrix at Contact Sites That Join the Inner and Outer Membranes

24. N-terminal signal sequence is recognized by receptors of TOM; The protein is translocated across both Mit membranes at or near special contact sites.

25. ATP Hydrolysis and a H+ Gradient are Used to Drive Protein Import into Mitochondria.

26. Proper folding ensure the maturation of Mitochondria proteins.
After the initial interaction with mitochondrial hsp70, many imported proteins are passed on to another chaperone protein, mitochondrial hsp60 that facilitates its folding by binding and releasing it through cycles of ATP hydrolysis.

27. Protein Transport into the Inner Mitochondrial Membrane and the Intermembrane Space Requires Two Signal Sequences

28. Origin and replication of mitochondria
Origin of mitochondria
Many of the features of the mitochondrial genetic system resemble those found in prokaryotes like bacteria. This has strengthened the theory that mitochondria are the evolutionary descendants of a prokaryote that established an endo-symbiotic relationship with the ancestors of eukaryotic cells early in the history of life on earth.

29. Mitochondria replication
Mitochondria replication much like bacterial cells. When they get too large, they undergo fission. This involves a furrowing of the inner and then the outer membrane as if someone was pinching the mitochondrion. Then the two daughter mitochondria split.

30. II Cellular respiration and Energy Conversion
Cellular respiration is the process of oxidizing food molecules to carbon dioxide and water. The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.
The process occurs in two phases:
Glycolysis: the breakdown of glucose to pyruvic acid
oxidation of pyruvic acid to carbon dioxide and water

31. Pathway of oxidation I: Glycolysis
The series of reaction by which 1 molecule of glucose is converted to 2 molecule of pyruvic acid
Yield: 2 ATP+ 2NADH2
Characteristics:
Does not require oxygen
Takes place in cytosol

32. II: Conversion of pyruvic acid to acetyl CoA.
2 pyruvic acid acetyl CoA (coenzyme A)
Yield: 2 NADH2
takes place in matrix of mitochondria

33. III: Citric Acid Cycle( Krebs cycle, TCA cycle). Characteristics:
Requires the presence of Oxygen (aerobic)
takes place in the inner membrane of the mitochondria.
2FADH2+ 6NADH2+ 2 ATP
The electrons of NADH and FADH2 are transferred to the respiratory chain

34. 1ATP

35. IV: Electron transport system and oxidative phosphorylation
The electron (hydrogen) transport chain is the final pathway for all electrons removed from substrate molecules during oxidation; consists mainly of enzymes of the cytochrome group.

36. Molecular basis of oxidative phosphorylation: A The Respiratory Chain
The respiratory chain consists of 3 complexes of integral membrane proteins
the NADH dehydrogenase complex
the cytochrome c reductase complex
the cytochrome c oxidase complex
and two freely-diffusible molecules
ubiquinone (coenzyme Q)
cytochrome c
that shuttle electrons from one complex to the next.

38. Molecular basis of oxidative phosphorylation:
B. 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 3:3:1:1:1
F0: 1a：2b：12c

39. Proton translocation through F0 drives ATP synthesis by F1: Binding Change Model and rotational catalysis
Boyer proposed in 1979

40. Electron-transport and oxidative phosphorylation

41. C. Mitchell’s Chemiosmotic theory
NADH and FADH2 carry protons (H+) and electrons (e-) to the electron transport chain located in the membrane.
The respiratory enzyme complexes couple the energetically favorable transport of electrons to the pumping of H+ out of the matrix and creates an electrochemical gradient or proton motive force.
As the accumulating protons follow the electrochemical gradient back across the membrane through an ATP synthase complex, the movement of the protons (proton motive force) provides energy for synthesizing ATP from ADP and phosphate.

44. Summary of glucose Oxidation.
Oxidative phosphorylation is the mechanism by which the free energy of electron is used to convert ADP to ATP :
Each pair of electron in NADH2 generates 3 ATP
Each pair of electron in FADH2 generates 2 ATP
(1) Glycolysis:
2*2H 2NADH2,each yielding 3ATP(total:6ATP)
(2) Oxidation of pyruvic acid to acetyl CoA
2*2H 2NADH2,each yielding 3ATP (total: 6ATP)
(3)Oxidation of acetyle COA in Citric acid cycle.
2*2H 2FADH2,each yielding 2ATP
6*2H 6NADH2,each yielding 3ATP
(total: 22ATP)

45. Glucose + 6 O2 6 CO2 +6H2O +38ATP+heat
The total yield of ATP is 34 ATP, about 90% of all the ATP generated by the oxidation of 1 glucose.
Thus the complete oxidation of 1 glucose generates a grand total of 38 ATP (adding 2ATP produced directly during glycolysis and 2ATP during TCA cycle).
Glucose + 6 O CO2 +6H2O +38ATP+heat

46. Mitochondria and Apoptosis
Induction phase
Effector phase
Degradation phase
Xiaodong Wang, Ph.D

47. Mitochondrial Disease
Mitochondrial diseases are the result of either inherited or spontaneous mutations in mtDNA or nDNA which lead to altered functions of the proteins or RNA molecules in mitochondria.
mtDNA mutation
Mitochondrial dysfunction
Mitochondrial-based diseases

48. Characteristics of mitochondrial disease
Mitochondrial mutations have a high ratio.
maternal inheritance
Thresholel effect

49. 1 diseases caused by mtDNA mutation
Leber hereditary optic neuropathy
Parkinson’s diseases

50. Parkinson’s Disease Named after English doctor James Parkinson
Affects 1-2% of individuals over 60 years old
Motor syndrome
Akinesia失去活动能力
Rigidity僵硬
Tremor震颤
imbalance
Handwriting of a person affected by PD in Lectures on the diseases of the nervous system by Charcot (1879). The original description of the text states "The strokes forming the letters are very irregular and sinuous, whilst the irregularities and sinuosities are of a very limited width. (...) the down-strokes are all, with the exception of the first letter, made with comparative firmness and are, in fact, nearly normal — the finer up-strokes, on the contrary, are all tremulous in appearance (...)."

51. Summary