MITOCHONDRIA ,STRUCTURE ,Mt DNA ,PROTEIN TRANSPORT,ETC,OXIDATIVE PHOSPHORYLATION

introduction, structure , functions,how proteins are transported into mitochondria,functions,electron transport chain,oxidative phosphorylation with animated videos

1. MITOCHONDRIA LOKESH PANIGRAHI M.Sc. BIOTECHNOLOGY 1 ST YEAR

2. CONTENTS INTRODUCTION MORPHOLOGY STRUCTURE FUNCTIONS ELECTRON TRANSPORT CHAIN OXIDATIVE PHOSPHORYLATION

3. Mitochondria are small granular or filamentous bodies which are present in the cytoplasm of eukaryotic cell and also known as the “ power house of the cell “

4. Introduction First observed by kolliker as granular structures in the straited muscles Flemming named them as fila Richard altman named them as bioblast The name mitochondria was coined by carl benda Michaelis used the supravital stain janus green as a vital dye

5. Mitochondria... Double membrane bound organisation They are energy converting organelles Present in all eukaryotic cells They are sites of aerobic respiration Mito – thread Chondrion - granule like Power house of the cell Mitochondria are semi autonomous organelle because they have their own genetic materials

6. Why do an organel contain DNA of its own..??

7. ENDO SYMBIOTIC THEORY

8. Endo symbiotic theory Endo means one inside the other symbiosis means living together Mitochondria and chloroplast were originally prokaryotes that came to live inside of other cells thereby creating a symbiotic relationship

9. Evidence to support endosymbiotic theory... Self replicating like bacteria Divide by binary fusion like bacteria Inner layer is similar in composition to bacteria Mito DNA is structurally similar to bacterial DNA Ribosomes,enzymes and transport systems are similar to bacteria Same size as bacteria Protein synthesis is inhibited by a variety of antibiotics is similar to that of bacteria

10. Morphology... Size -  0.05 – 1.0 µm in diameter. Length - 1 – 10 µm long Shape - Bean shaped , in fibroblast it is elongated and thread like. Number - it vary from cell to cell ex: In rat liver it may be few to 5oo In sea urchins it may be from 13000 to 14000 Location – cell with high energy requirements ex: sprem cell , muscle etc.,

11. Structure... Outer membrane Inner membrane Intermembrane space Cristae Matrix

12. OUTER MEMBRANE Simple phospholipid bilayer . Fairly smooth It encloses the mitochondrion. Containing protein structures called porins . porins allows the free passage for various molecules into the intermebrane space of the mitochondria

13. INNER MEMBRANE Is freely permeable only to oxygen, CO₂ , H₂O . Inner membrane is convoluted forming folds called cristae Impermeable to many solutes due to high content of phospholipid called cardiolipin The cristae generally increases the inner membrane surface area The two faces of membrane are referred to as the matrix side (N –side) and the cytosolic side (P –side)

14. Inter membrane space...  It is also known as Perimitochondrial space . The space between inner membrane and outer membrane . It has high proton concentration . . Proteins present, participate in ATP synthesis

15. MATRIX Gel like consistency Dense ,homogenous 2/3rd of total protein of mitochondria Mitochondria have: - enzymes , ribosomes ,DNA ,mRNA ,granules ,fibrils ,tubules. Major enzymes include enzymes involved in: -Synthesis of nucleic acid and proteins -Fatty acid oxidation -TCA CYCLE (except succinate dehydrogenase )

16. CRISTAE Inner membrane is thrown up into a series of folds called cristae (animals ) or tubuli or microvilli (plants) which expand its surface area , enhancing its ability to produce ATP. cristae is covered with this inner membrane spheres called stalked particles or knobs or heads.

17. Mitochondrial division Divide by binary fusion Similar to bacteria It is mediated by a conserved, large dynamic- related GTPase called DnmI (in yeast , DrpI (in mammals) These proteins aggregates in ring or spiral like structures around the outer surface of mitochondria at regions where mitcochondria soon to divide

18. Site of several metabolic reactions ... Outer membrane : Oxidation of epinephrine Degradation of tryptophan Elongation of fatty acid Inner membrane : oxidative phosphorylation Matrix : Kreb’s cycle Beta oxidation Detoxification of ammonia in urea cycle Storage of calcium ions

19. MITOCHONDRIAL DNA  Small, Double stranded ,covalently closed ,circular molecule. It is made up of one heavy strand and one light strand Occurs in multiple copies. It has 16569 bp . Most usually remains attached to inner mitochondrial membrane. Stores biological info required for growth and multiplication of mitochondria. Can undergo replication and duplication. and it is different from that of nuclear DNA

20. MITOCHONDRIAL DNA Mitochondrial DNA is inherited meternally Heteroplasmy and replicative segreegation : mitochondial DNA vary from one person to another person of same species Different stop codons are present in the mitochondrial DNA : AGA AAG but not UGA High mutation rate And it is totally under the control of the nuclear DNA

21. Why mitochondrial DNA is inherited meternally ..??

22. Mitochondrial DNA is inherited meternally because Female ovum has nucleus as well as mitochondria and male sperm has only nucleus in their head region Mitochondria is present only in the tail region of sperm for their motility but not in head region So when they fuse nuclear from both the parents will fuse but the mitochondrial DNA will only come from female but not from male

23. How proteins are transported into mitochondria..??

24. Transport of proteins Mitochondrial proteins are synthesized by 80S cytosolic as well as 70S matrix ribosomes About 99% of mitochondrial proteins are encoded by nuclear genes and are synthesized as precursors on cytosolic ribosomes Proteins imported into mitochondria may be located in the outer membrabe , the intermembrane space ,the inner membrane or the matrix

25. Transport of proteins Before entering into the transport of proteins we should know the following 1.mitochondrial targeting signal sequence 2.TOM complex ( translocase of outer membrane) 3.TIM complex ( translocase of inner membrane) 4.Hsc ( cytosolic chaperons) 5.MPP (mitochondrial processing peptidase) 6.PAM ( presequence translocase associated motor) 7.OXA complex 8.SAM ( sorting and assembly machinery)

26. Transport of proteins TIM complex - outer membrane TOM complex - inner membrane MPP - in matrix SAM - outer membrane OXA - inner membrane

27. Transport of proteins 1. targeting of mitochondrial proteins 2. Mitochondrial targeting sequences 3. Targeting of mitochondrial proteins into the mitochondrial matrix 4. Targetting to inner membrane 5. Targetting to outer membrane

28. Functions... Energy transducer of the cell (synthesis of ATP) Krebs cycle in matrix ETC Phosphorylation - ATPase Storage and transport of ATP : the ATP that are produced as a result of cellular respiration are liberated through a transporter called adenine nucleotide translocase Enzymes required for the synthesis of lipids are present in the mitochondria Production of heat (non shivering thermogenesis )

29. FUNCTIONS Role in apoptosis ( programmed cell death). Synthesis of estrogen and testosterone. Role in neurotransmitter metabolism. Role on cholesterol metabolism . Role in heme synthesis .

30. GLYCOLYSIS

31. ELECTRON TRANSPORT CHAIN  The ETC consists of five separate protein complexes: Complex I , II, III, IV and V. The complexes I, II, III and IV are involved in transportation of electrons to molecular oxygen. The complex V is involved in the synthesis of ATP. Each complex consists of certain prosthetic groups Prosthetic groups are the electron carriers.

32. Complex I COMPLEX I - NADH Dehydrogenase Large multisubunit complex with about 40 polypeptide chains PROSTHETIC GROUPS : 1.) FMN 2.) FE-S center ( atleast six) NADH that is formed will enter at complex I After the transfer of electrons from complex I to coenzyme Q there is a net trasfer of 4 protons to the intermembrane space

33. Coenzyme Q Also known as ubiquinone Is a benzoquinone linked to a number of isoprene units Q refers to the quinone c hemical group It is the only electron carrier in the electron transport chain that is not a protein bound prosthetic group Fully oxidised – ubiquinone Q Fully reduced - ubiquinol QH2

34. COMPLEX II Also called as succinate dehydrogenase Entry gate for F ADH Succinate dehydrogenase (from the citric acid cycle) directs transfer of electrons from succinate to CoQ via FADH2. • Acyl-CoA dehydrogenase (from oxidation of fatty acids) also transfers electrons to CoQ via FADH2. No transfer of protons from matrix to the intermembrane space

35. COMPLEX III  Complex III ( cytochromes bc1) • Electron transfer from ubiquinol to cytochrome c. At the end of cytochrome III net transfer of 4 protons into the intermembrane space.

36. COMPLEX IV Combination of cytochromes a and a3, 10 protein subunits 2 types of prosthetic groups: 2 heme and 3 Cu ion • Electrons are delivered from cytochromes a and a3 to O2. At the end of complex IV, net transfer of 4 protons into the intermitochondrial space

37. COMPLEX V Also called as ATP synthase Embedded in the inner membrane Made up of F0 and F1 complexes F1 - 9 subunits F0 – 3 subunits The F0 subcomplex is composed of channel protein ‘C’ subunit to which F1 synthase is attached

38. Inhibitors of electron transport Rotenone –inhibits transfer of electrons through complex I Amobarbital – inhibits electron transport through complex I Antimycin – blocks electron transport at the level of the complex III Cyanide,azide and carbon monoxide bind with complex IV and inhibit the terminal transfer of electrons to oxygen

39. Piericidin –antibiotic block the transfer of elctrons at complex I by competing with Q

40. OXIDATIVE PHOSPHORYLATION The chemiosmotic theory, proposed by Peter Mitchell in 1961, postulates that the two processes are coupled by a proton gradient across the inner mitochondrial membrane so that the proton motive force caused by the electrochemical potential difference (negative on the matrix side) drives the mechanism of ATP 

41. OXIDATIVE PHOSPHORYLATION- CHEMIOSMOSIS As the electrons are transferred, some electron energy is lost with each transfer. This energy is used to pump protons (H+) across the membrane from the matrix to the innermembrane space. A proton gradient is established . 

42. OXIDATIVE PHOSPHORYLATION- CHEMIOSMOSIS The higher negative charge in the matrix attracts the protons (H+) back from the intermembrane space to the matrix. The accumulation of protons in the intermembrane space drives protons into the matrix via diffusion. Most protons move back to the matrix through ATPsynthase . ATP synthase uses the energy of the proton gradient to synthesize ATP from ADP + Pi.