Mitochondria

Mitochondria are membrane-bound cell organelles (mitochondrion, singular), known as the power house of the cell that generate most of the chemical energy needed to power the cell's biochemical reactions. Mitochondria generates most of the cell's supply of adenosine triphosphate (ATP), by a process called
“oxidative phosphorylation”.

1. Anup Muni Bajracharya

2. Mitochondria
•Mitochondria (singular, mitochondrion)
•Greek,mitos, "thread", and,chondrion,
"granule"or "grain-like".
•are typically tubular or rod-shaped organelles
•found in the cytoplasm of most cells
•produces enzymes for the metabolic conversion
of food to energy.
•called the 'powerhouse of the cell' as they
produce about 90% of the chemical energy that
cells need to survive.
•generate most of the cell's supply ofadenosine
triphosphate (ATP), by a process called
“oxidative phosphorylation”.

3. History
•The mitochondria were first observed by Kollikerin 1850
as granular structures in the striated muscles of insects.
•In 1882 Flaming named the mitocondriaas Fila
•In 1890, Richard Altmannnamed this organelle as
Bioblast.
•The present name mitochondria was given by Benda .
•In 1912 Kingsburrysuggested that oxidation reactions
mediated by mitochondria are normal cellular process.
•Otto Warbergis father of respirometry who isolated large
granule , mitochondria and showed that these granules
contained enzyme catalyzing oxidative cellular reactions.

4. History

5. Structure of Mitochondria
•Morphologically mitochondria may be in the form of
filaments or small granules.
•These may assume rod-like shape called
chondriosomeswhich may enlarge or aggregate to
form massive spheroid bodies called
chondriospheres.

6. Localisation/Position
•Mitochondria are present in all eukaryotic
cells.
•They move autonomously in the cytoplasm, so
they generally have uniform distribution in the
cytoplasm, but in many cells their distribution
is restricted.
•The distribution and number of mitochondria
can be correlated with type of function the
cell performs.

7. Localisation/Position
•Mitochondria lie freely in cytoplasm, possessing power of
independent movement and may take the form of filaments.
•In some cells they can move freely,
•In others they are located permanently near the region of the cell
where more energy is needed.
•E.g., in the rod and cone cells of retina mitochondria are located in
the inner segment,
•in cells of kidney tubules they occur in the folds of basal regions
near plasma membrane,
•in neurons they are located in the transmitting region of impulse,
•in certain muscle cells (e.g. diaphragm), mitochondria are grouped
like rings or bracers around the I-band of myofibril.
•Mitochondria are particularly numerous in regions where ATP-
driven osmotic work occurs,e.g.,brush border of kidney proximal
tubules.

8. Number
•varies from cell to cell and from species to
species.
•A few algae and some protozoan have only
single mitochondria.
•Their number is related to the activity, age
and type of the cell.
•Growing, dividing and actively synthesizing
cells contain more mitochondria than the
other cells.
•In Amoeba (Chaos chaos), there may be as
many as 50,000 mitochondria.
•In rat liver cells, these are few in number,
about 1000 to 1600. Some Oocytes contain
as many as 3, 00,000 mitochondria.
Mitochondrion from
the amoeba Chaos
carolinensis,

9. Shape and size
•may be filamentous or granular in shape
•may change from one form to another depending
upon the physiological conditions of the cells.
•Thus, they may be of club, racket, vesicular, ring or
round-shape.
•Eg-granular in primary spermatocyte or rat, or club-
shaped in liver cells.
•Size:Normally mitochondria vary in size from 0.5 μm
to 2.0 μmand, therefore, are not distinctly visible
under the light microscope. Sometimes their length
may reach up to 7 μm.

10. Structure
•Each mitochondrion is bound by two highly specialized
membranes
•Inner and the outer membrane
•The membranes are made up of phospholipids and
proteins.
•The space in between the two membranes is called the
inter-membrane space which has the same
composition as the cytoplasm of the cell.
•Inner and the outer membrane is separated by a 6–8
nm wide space.

11. Outer Membrane
•The outer membrane, composed of about half lipid and half
protein
•contains porinsthat render the membrane permeable to
molecules having molecular weights as high as 10,000 dalton.
•the outer membrane of mitochondria is similar to the outer
membrane of gram-negative bacteria.
•The outer membrane is smooth unlike the inner membrane
•It has a large number of special proteins called porinsthat allow
molecules of 5000 daltonsor less in weight to pass through it.
•It is completely permeable to nutrient molecules, ions, ATP and
ADP molecules.

13. Inner membrane
•The inner membrane is much less permeable, than the outer membrane.
•It has about 20 percent lipid and 80 percent protein.
•The surface area of the inner membrane is greatly increased by a large
number of infoldings, or finger like projections called cristae
•Cristae that protrude into the matrix,orcentral space, increasing the
surface area for the complexes.
•It contains the complexes of the electron transport chain and the ATP
synthetasecomplex
•It is permeable only to oxygen, carbon dioxide and water and is made up
of a large number of proteins that play an important role in producing ATP,
and also helps in regulating transfer of metabolites across the membrane.
•In general, the cristae of plant mitochondria are tubular, while those of
animal mitochondria are lamellar or plate-like.

14. Matrix
•Theinner membraneencloses
a space filled with a fluid
calledmatrix. Or
•The space between the cristae
called the inner chamber is
filled with a gel like material
termed the mitochondrial
matrix.
•It contains proteins, lipids,
some ribosomes, RNA, one or
two DNA molecules and
certain fibrils, crystals and
dense granules

15. Cristae
•The inner mitochondrial membrane bears plate like infoldingscalled
the cristae.
•They extend inwards to varying degrees, and may fuse with those
from the opposite side, dividing the mitochondrion into
compartments.
•The active cells may have numerous cristae whereas the inactive cells
may have only a few. The cristae have in them a narrow intra-crista
space. It is continuous with the inter-membrane space.
•The cristae greatly increase the inner surface of the mitochondrion to
provide enough space for housing enzyme assemblies.
•The cristae also allow for expansion or swelling of mitochondria under
different metabolic and environmental conditions.
In cells of the proximal parts of the kidney tubules, the cristae are longitudinal
folds parallel to the long axis of mitochondrion.
In many protozoans, in insect flight muscles cells and in adrenal endocrine cells
the cristae are tubular.
Cristae are lamellar in hepatocytes.
In heart muscle cells cristae are zig-zag. They also vary in number.

16. Oxysomes
•The inner mitochondrial
membrane bears minute
regularly spaced particles
known as the inner membrane
subunits or
•elementary particles (EP) or
•oxysomes.
•An oxysomeconsists of three
parts-
•a rounded head piece or F1
subunit joined by a short stalk
to a base piece or F0 subunit
located in the inner membrane.
•There may be 100,000 to
1000,000 oxysomesin a single
mitochondrion.

17. Chemical composition
Mitochondria are found to contain
65 to 70 per cent proteins,
25 to 30 per cent lipids,
0.5 per cent RNA and
small amount of the DNA.
lipid contents -around 90 per cent
phospholipids (lecithin and cephalin),
5 per cent or less cholesterol and
5 per cent free fatty acids and triglycerides.
The outer mitochondrial membrane
has typical ratio of 50 per cent
proteins and 50 per cent
phospholipids of ‘unit membrane’.
However, it contains more unsaturated
fatty acids and less cholesterol.
The inner membrane is rich in one
type of phospholipid, called
cardiolipinwhich makes this
membrane impermeable to a variety
of ions and small molecules (Na+, K+,
Cl-, NAD+,AMP, GTP, CoA and so on).

18. Function of mitochondria
FOOD
DIGESTION
SIMPLER FORMS
(Glucose, Aminoacids, Fattyacids)
RELEASES NADH2, FADH2
SENT TO MITOCHONDRIA
OXIDATIVE PHOSPHORYLATION
The most important function of the mitochondria is
to produce energy.
'power house' of the cell
Different pathways

19. •It is important to maintain proper concentration of
calcium ions within the various compartments of the
cell.
•Mitochondria help the cells to achieve this goal by
serving as storage tanks of calcium ions.
Function of mitochondria

20. •Mitochondria help in the building of certain
parts of the blood, and hormones like
testosterone and estrogen.
•Mitochondria in the liver cells have enzymes
that detoxify ammonia.
Function of mitochondria