3. *
*A cellular organelle probably of
endosymbiotic origin that resides in the
cytosol of most nucleated (eurkaryotic)
cells.
* This organelle produces energy by
oxidising organic acids and fats with
oxygen by the process of oxidative
phosphorylation and generates oxygen
radicals (reactive oxygen species ROS
)as a toxic by-product
4. *
*Kallikar(1850) was first to describe muscle mito
which he called Sarcosome.
*Altman called them Bioblasts
*Flemming (1882)coined the word filia for them
*Benda(1897) introduced the term
Mitochondrion to designate thread like granules
7. *
* Each cell contains many mitochondria, each
of which contains multiple copies of 16.5-k-b
circular DNA molecule
*The mitochondrial genome is subject to a
number of peculiarities of inheritance
9. Outer membrane:
• The outer mitochondrial membrane, which encloses the
entire organelle, has a protein-to-phospholipid ratio similar
to that of the eukaryotic plasma membrane (about 1:1 by
weight)
• . It contains large numbers of integral proteins called
porins. These porin form channels that allow molecules
5000 Daltons or less in molecular weight to freely diffuse
from one side of the membrane to the other.
• Larger proteins can enter the mitochondrion if a signal
sequence at their N-terminus binds to a large multisubunit
protein called translocas of the outer membrane, which
then actively moves them across the membrane
10. Intermembrane space
• The intermembran space is the space between the outer
membrane and the inner membrane. It is also called as
Perimitochondrial space.
• Because the outer membrane is freely permeable to small
molecules, the concentrations of small molecules such as
ions and sugars in the intermembrane space is the same as
the cytosol.
• However, large proteins must have a specific signaling
sequence to be transported across the outer membrane, so
the protein composition of this space is different from the
protein composition of the cytosol
• One protein that is localized to the intermembrane space in
this way is cytochrome c
11. The inner mitochondrial membrane contains proteins with five
types of functions:
• Those that perform the redox reactions of oxidative
phosphorylation
• ATP synthase, which generates ATP in the matrix
•Specific transport proteins that regulate metabolite passage into
and out of the matrix
• Protein import machinery.
• Mitochondria fusion and fission protein.
Almost all ions and molecules require special membrane
transporters to enter or exit the matrix. Proteins are ferried
into the matrix via the translocase of the inner membrane
(TIM) complex or via Oxa1.
*
12. • The inner mitochondrial membrane is compartmentalized
into numerous cristae, which expand the surface area of the
inner mitochondrial membrane, enhancing its ability to
produce ATP.
• For typical liver mitochondria, the area of the inner
membrane is about five times as great as the outer membrane.
This ratio is variable and mitochondria from cells that have a
greater demand for ATP, such as muscle cells, contain even
more cristae.
• These folds are studded with small round bodies known as F1
particles or oxysomes. These are not simple random folds but
rather invaginations of the inner membrane, which can affect
overall chemiosmotic function.
One recent mathematical modeling study has suggested that the
optical properties of the cristae in filamentous mitochondria
may affect the generation and propagation of light within the
tissue.
*
13. • The matrix is the space enclosed by the inner membrane. It
contains about 2/3 of the total protein in a mitochondrion.
• The matrix is important in the production of ATP with the aid
of the ATP synthase contained in the inner membrane.
• The matrix contains a highly-concentrated mixture of
hundreds of enzymes, special mitochondrial ribosomes
tRNA, and several copies of the mitochondrial DNA genome.
Of the enzymes, the major functions include oxidation of
pyruvate and fatty acids, and the citric acid cycle.
• Mitochondria have their own genetic material, and the
machinery to manufacture their own RNAs and proteins A
published human mitochondrial DNA sequence revealed
16,569 base pairs encoding 37 total genes: 22 tRNA, 2
rRNA, and 13 peptide genes.
*
14. Function
•The most prominent roles of mitochondria are to produce the
energy currency of the cell, ATP (i.e., phosphorylation of
ADP), through respiration, and to regulate cellular metabolism.
•The central set of reactions involved in ATP production are
collectively known as the citric acid cycle, or the Krebs Cycle.
However, the mitochondrion has many other functions in addition
to the production of ATP.
• Regulation of the membrane potential
•Apoptosis-programmed cell death
• Calcium signaling (including calcium-evoked apoptosis)
• Regulation of cellular metabolism
• Certain heme synthesis reactions.
• Some mitochondrial functions are performed only in specific
types of cells. For example, mitochondria in liver cells contain
enzymes that allow them to detoxify ammonia, a waste product
of protein metabolism.
15. *
Nuclear Genome Mitochondrial Genome
Size 3200 Mb 16.6 kb
No. of different DNA
molecules
23 (in XX cells) or 24
(in XY cells); all linear
One circular DNA
molecule
Total no. of DNA
molecules per cell
46 in diploid cells, but
varies according to
ploidy
Often several
thousands (but variable
Associated protein Several classes of
histone & nonhistone
protein
Largely free of protein
No. of genes ~ 30 000 ~35-000 37
Gene density ~ 1/100 kb 1/0.45 kb
16. *
Repetitive DNA Over 50% of genome Very little
Transcription The great bulk of genes are
transcribed individually
Co-transcription of
multiple genes from both
the heavy and light strands
Introns Found in most genes Absent
% of coding DNA ~ 1.5% ~ 93%
Codon usage Slightly different see slide
Recombination At least once for each pair
of homologs at meiosis
No evidence for this
occurring naturally
Inheritance Mendelian for sequence on
X and autosomes; paternal
for sequence on Y
Exclusively maternal
17. *The membrane is smooth
*Protein content is roughly
equal to that of lipids
.
Enzymes-
* Monoamino oxidase
*NADH cytochrome
reductase
*Hexokinase2-
Glycerophosphate acyl
transferase
*Membrane bears larger
umber of F0-F1 particles
*Protein content is
80%while lipid is low
Enzymes-
*ATPase
*Succinic dehydrogenase
*Cytochrome oidase
*3-Hydroxy butyrate
dehydrogenase
*
18. An affected woman transmits the trait to
all her children. Affected men
(represented by squares do not pass
the trait to any of their offspring
Maternal genetic
transmission
19. *
*Most somatic cells 100-10,000
*Lymphocyte 1000
*Oocytes
100,000
*Sperm few
hundred
*No mitochondria in red cells and some
terminally differentiated skin cells
20. *
MERRF (Myoclonic Epilepsy with Ragged Red
Fibres
MELAS (Myopathy,Epilepsy Lactic
acidosis,Stroke-like episodes
LHON (Leber’s Hereditary Optic atrophy)
Kearn-Sayre (eye problems,heart
block,ataxia ie loss of coordination
Leigh syndrome(rare severe brain disease
in infancy,also heart problems)
21. *
Depends on:-
•High mutation rate (especially in
D loop region)
•Maternal transmission
•No recombination
This allows the origins of female ancestors to be deduced
22. *
*Many workers believe the
mitochondria of eukaryotic cell
to have arisen from a
prokaryotic cell which invaded
another eukaryotic cell in the
recent past.this assumption is
based on the fact that the mito
has a single ringed DNA
molecule like that of the
prokaryotic cell.
