Brief introduction on mitochondria

1. CELL BIOLOGY.
MITOCHONDRIA.

2. ANIMAL CELL – MITOCHONDRIA.

3. INTRODUCTION.
 MITOCHONDRIA are important cell organelles,
essential for aerobic respiration of eukaryotic cell.
They are popularly called as “POWER HOUSES
OF CELL” because they are the centre of release of
energy.
 Mitochondria was first observed by Kolliker in
1880.

4. Two mitochondria from mammalian lung tissue displaying
their matrix and membranes as shown by electron
microscopy.

5. LOCATION.
 Mitochondria are found in nearly all eukaryotes.
They vary in number and location according to cell
type.
 A single mitochondrion is often found in
unicellular organisms.
 Conversely, numerous mitochondria are found in
human liver cells, with about 1000–2000
mitochondria per cell, making up 1/5 of the cell
volume.

6. STRUCTURE.
 The size & shape of mitochondria varies. They are
small rod- shaped or spherical structures present
in the cytoplasm of the cells which show aerobic
respiration. The shape depends upon the
physiological condition of the cell.
 SIZE:- The size of the mitochondria may vary
from cell to cell. Usually, it is 0.2µ to 1.0µ in
diameter. 2 to 8µ in length.

7. MORPHOLOGY.
 Each mitochondrium is bounded by 2 membranes, the outer &
inner membrane.
 These membranes are lipo-proteinic in nature.
 In between the 2 membranes, there is a space called as peri-
mitochondrial space of 80A° width.
 The outer membrane is 60-75 A° thick, it forms outer covering.
 The inner membrane is 50-70 A° thick, it forms a number of finger-
like or plate-like infolding into the cavity of mitochondria called as
CRISTAE.
 This cavity is filled with fine granular mitochondrial matrix,
which is gel – like & contains proteins, lipids, circular DNA
molecules, 70s ribosomes & certain granules.

8. MORPHOLOGY.
 Under high resolving power of electron microscope
studies have shown numerous stalked knob – like
projections, called as elementary particles or
oxysomes or F̥ - F1 particles or Racker’s
particles, on the inner membrane & cristae.
 Each particle consists of a base, stalk & a head.
They contain all enzymes involved in ETC &
enzymes for oxidative phosphorylation. Hence,
these are called as electron transport particles
(ETP).

9. Structure of Mitochondria.

10. CHEMICAL COMPOSITION.
 The chemical composition of the mitochondria varies
in different animal and plant cells.
 Enzymes of outer membrane:- Mono amine oxidase,
kynurenine hydroxylase, fatty acid Co ligase etc. These
are involved in mitochondrial lipid synthesis & in the
conversion of lipid substrate into forms that are
subsequently metabolized in the matrix.
 Enzymes of inter-membrane space:- It contains
several enzymes that use ATP passing out of the matrix
to phosphorylate other nucleotides. The main enzymes
are adenylate kinase & nucleoside diphosphokinase.

11. CHEMICAL COMPOSITION.
 Enzymes of inner membrane:- Enzymes of inner
membrane are the enzymes of electron transport
pathways – nicotinamide adenine dinucleotide
(NAD), flavin adenine dinucleotide (FAD),
diphosphopyridine nucleotide dehydrogenase, ATP
synthetase, succinate dehydrogenase etc.
 Enzymes of mitochondrial matrix:- Malate
dehydrogenase, isocitrate dehydrogenase, citrate
synthetase, beta oxidation enzymes.

12. MITOCHONDRIAL DNA.
 Mitochondrial DNA or mtDNA or mDNA.
 The mitochondria has a small amount of DNA of their
own. Human mitochondrial DNA spans about
16,500 DNA base pairs, it represents a small fraction
of the total DNA in cells. The mtDNA contains 37
genes. All these genes are essential for normal function
of the mitochondria.
 These DNA help the mitochondria divide
independently from the cell.
 The mtDNA in most multicellular organisms is
circular, covalently closed, double-stranded DNA.

13. FUNCTIONS.
 The most important function of the mitochondria is to
produce energy. The simpler molecules of nutrition are
sent to the mitochondria to be processed and to produce
charged molecules. These charged molecules combine with
oxygen and produce ATP molecules. This process is known
as oxidative phosphorylation.
 Mitochondria help the cells to maintain proper
concentration of calcium ions within the compartments of
the cell.
 The mitochondria also help in building certain parts of
blood and hormones like testosterone and estrogen.
 The liver cells mitochondria have enzymes that detoxify
ammonia.