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
1ST 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 SYMBIOTICTHEORY

8. Endosymbiotictheory
 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

14. OUTERMEMBRANE
 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

15. INNERMEMBRANE
 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)

16. Intermembranespace...
 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

17. 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)

18. 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.

19. Mitochondrialdivision
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

20. Siteofseveralmetabolicreactions...
 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

21. 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

22. 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

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

27.  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

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

29. Transportof 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

30. Transportof 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)

31. Transportof proteins
 TIM complex - outer membrane
 TOM complex - inner membrane
 MPP - in matrix
 SAM - outer membrane
 OXA - inner membrane

32. Transportof 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

36. 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)

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

38. GLYCOLYSIS

41. ELECTRONTRANSPORTCHAIN
 The ETC consists of five separate protein
complexes: Complex I , II, III, IV andV.
 The complexes I, II, III and IV are involved in
transportation of electrons to molecular
oxygen.
 The complexV is involved in the synthesis of
ATP.
 Each complex consists of certain prosthetic
groups
 Prosthetic groups are the electron carriers.

43. ComplexI
 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

45. CoenzymeQ
 Also known as ubiquinone
 Is a benzoquinone linked to a number of
isoprene units
 Q refers to the quinone chemical 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

46. COMPLEX II
 Also called as succinate dehydrogenase
 Entry gate for FADH
 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

48. 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.

50. 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

52. 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

55. Inhibitorsofelectrontransport
 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

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

57. OXIDATIVEPHOSPHORYLATION
 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

58. OXIDATIVEPHOSPHORYLATION-
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.

59. OXIDATIVEPHOSPHORYLATION-
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.