Mitochondria are membrane-bound organelles found in eukaryotic cells that produce energy through respiration. They were first observed by Richard Altmann and named by Benda. Mitochondria have an outer and inner membrane, with cristae extending inward from the inner membrane. They contain their own DNA and ribosomes. Mitochondria play key roles in cellular metabolism and energy production.

1. BY
N.VIJAY

2.  Mitochondria are membrane bound cell organelles found in
most eukaryotic cells .
 It was first identified as “BIOBLASTS” by RICHARD
ALTMANN.
 BENDA coined the term mitochondria.
 In Greek ‘mitos’ means filament and ‘chondros’ means
granules

3.  They are believed to be derived from endo-symbiotic
prokaryotes.
 They are described as power houses of the cell
 It is a semi autonomus cell organelle.

4. Shape :
 These are filamentous or granular.
 They appear spherical to ellipsoid .
 They exhibit pleiomorphic appearance.
Size :
 Approximately 1µm thick and 1-3 µm long.
 Width 0.5 µm ( relatively constant).
 Length may vary ( maximum 7µm)

5. Distribution :
 They are uniformly distributed throughout the cytoplasm
where the energy is required.
Number :
 A plant cell may contain hundreds or thousands of
mitochondria.
 Their number varies depending upon the cell type and stage
of development .
 Ex : The central cells of maize root cap have approximately
200 when young and 2000 – 3000 at matured stage.

6. Mitochondrion is composed of :
 Outer mitochondrial membrane
 Inter membrane space
 Inner mitochondrial membrane
 Cristae
 Matrix

8.  It has a protein to phospholipid ratio of 1 : 1
 It contains large numbers of integral proteins called PORINS
 It associates in a structure called ‘MAM’
( MITOCHONDRIA ASSOCIATED ER MEMBRANE
 It is permeable to small molecules .

9.  It is also called as PERIMITOCHONDRIAL SPACE.
 It is the space between the outer and inner membranes.
 The concentrations of small molecules such as ions and
sugars is same as that of cytosol.
 In this space,the protein composition is different from that of
the cytosol.


10.  It is a highly convoluted membrane.
 It is much larger in area than the outer membrane.
 It folds into cristae that extend deeply into the matrix.
 It has a very high protein to phospholipids ratio of 3 : 1
 It contains 1/5 th of total protein of mitochondrion.
 It is highly impermeable to all molecules.

11. It contains proteins with 5 types of functions :
 those perform the redox reactions of oxidative
phosphorylation
 ATP-synthase
 Specific transport proteins
 Protein import machinery
 Mitochondria fission and fusion protein

12.  The inner membrane is compartmentalized into numerous
cristae.
 They are studded with small round bodies known as ‘F1
Particles’ or ‘Oxysomes’
 These particles have a spherical head about 9 nm in diameter
linked to the membrane by a short stalk.

14.  It is the space enclosed by the inner membrane.
 It contains about 2/3rd of the total protein in a mitochondrion.
 It is important in the production of ATP with the aid of ATP-
synthase.
 It contains a highly concentrated mixture of hundreds of
enzymes,special mt-ribosome,t-RNA and mt-DNA.

15.  These are smaller than those in the cytoplasm.
 They are 70s type and are composed of large sub units ( 50s )
and a small sub unit ( 30s ).
 The large sub unit contains two r-RNA molecules, one of 23s
and other of 5s.
 The small sub unit contains one r-RNA molecule of 16s.
 All these r-RNA molecules are coded by mitochondrial DNA.

16. Mt-DNA :
 Circular DNA of 16.6 kb
 Double stranded DNA
 Absence of histone proteins
 Multiple copies are present in nucleoid
 It encodes the enzymes required for oxidative
phosphorylation and mitochondrial electron transport.

17. The two DNA strands are different in base composition .
 H-strand (heavy) of high base composition
 L-strand (light) of low base composition
D-LOOP :
 It is a short region ( 1121bp) on DNA.
 It is a DNA triple helix contains two overlapping copies of
H-strand
 It is the site where most of the replication is controlled.
 No non coding DNA is present outside of the D-loop.

19.  The origin of replication for the H-strand is in the D-loop and
it is initiated by an RNA primer.
 After the new H-strand is about 2/3 complete ,the L-strand
origin of replication is uncovered.
 The L-strand origin is on the old H-strand ; it is uncovered
when the old H-strand is displaced by DNA polymerase
synthesizing the new H-strand.
 The L-strand origin folds into a stem loop structure which
acts as a primer and replication of the L-strand begins
 Replication can be said to be bi-directional.

20.  It produces ATP through respiration and regulate cell
metabolism.
 Chemical reactions of Krebs cycle takes place in
mitochondria
 Bio-genesis of mitochondrial ribosomes takes place in the
matrix.

21.  Participate in photo respiration in C3 plants .
 Glyoxalate cycle occurs in the matrix.
 It stores calcium a contribution process for cell
homeostasis

22.  They are single membrane bound cell organelles .
 They were first identified by CHRISTIAN DE DUVE.
 They are spherical in shape
 They are 0.2-1.7µm in size
 It consists of finely granular matrix

24.  Leaf peroxisomes :
◦ Catalyzes oxidation of side product of CO2 fixation in
photorespiration
 Glyoxysomes :
◦ Converts fatty acid in seed lipids into sugars needed for
growth in the young plant

25.  Detoxifying cell by degradation of H2O2 produced by the
perioxisomal oxidases.
 Leaf peroxisomes are involved in photo respiration
( Glycolate pathway)
 Breaking down fatty acids during germination of fat storing
seeds ( Glyoxylate cycle)
 They were involved in conversion of fixed nitrogen into
ureides for N-export