MITOCHONDRIAGreek - mitos, thread and chondrion, granule. : MITOCHONDRIAGreek - mitos, thread and chondrion, granule. "cellular power plants“ and also controlls
signaling, cellular differentiation, cell death, cell cycle and cell growth
Slide 2 : Dicovery :\
First observed in animal straited muscle cells by –Kolliker, 1880
First observed in plant, Nymphaea cells by Meeves ,1904
Credit of discovery goes to Flemming, 1882 called them as filia and Altmann, 1894 named them as bioplasts
Benda 1897 called them as mitochondria
Michaelis demonstrated their role in respiration
Benseley isolated them form liver cells
Size, shape and number : Size, shape and number 3-5 micron meter in length and 0.5 -2 micron in diameter
Cell enviromnment , pH and osmotic pressure etc. determine the size.
Spherical, oval,, or elliptical in shape
Alga, Microsterias, Chlamydomonas , chlorella & Trypanosoma etc. have single large mito, rat liver cells may have 1000-2500 mito, insect flight muscle-500,000, the protozoa, giant amoeba, Choas choas may have 50,000 mito, kidney cells 300-400, sperm cell-25-50
Green plant cell less mitochondria as compared to non-green cell.
Chondriome : Chondriome Mitochondrial system of a cell.
Chondriospheres –fused mitochondia-plants
Mito chow movements within cell- more pronounced in plants.
Mito can be stained by Janus green B stain/ GENTIAN VIOLET.
Absent in- anaerobic protozoa, mature RBC, prokaryotes.
Located in metabolically active regions of cell-
sandwitched between contractile elements in muscles,
in mid-piece in sperm surrounding contractile longitudinal elements,
near secretory surface in glands,
near absorbitive surfaces of intestinal cells & nephrons,
around spindle, &
base of cilia
Ultra-structure : Ultra-structure A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins- having different properties.
There are five distinct compartments within the mitochondrion.
There is the outer mitochondrial membrane,
the intermembrane space (the space between the outer and inner membranes),
the inner mitochondrial membrane,
the cristae space (formed by infoldings of the inner membrane), and
the matrix (space within the inner
Outer membrane : Outer membrane 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.
The mitochondrial outer membrane can associate with the endoplasmic reticulum (ER) membrane, in a structure called MAM (mitochondria-associated ER-membrane). This is important in ER-mitochondria calcium signaling and involved in the transfer of lipids between the ER and mitochondria.[
Intermembrane space : Intermembrane space Space between the outer membrane and the inner membrane
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.
Inner membrane : Inner membrane 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
Slide 9 : It contains more than 151 different polypeptides, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1 protein for 15 phospholipids)- 1/5 of the total protein in a mitochondrion
In addition, the inner membrane is rich in an unusual phospholipid, cardiolipin- contains four fatty acids rather than two and may help to make the inner membrane impermeable.
Is highly impermeable to all molecules.
Almost all ions and molecules require special membrane transporters to enter or exit the matrix..
Cristae : Cristae Invaginations , simple or branched- expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP.
Number- more in metabolically active cells-muscle cells and liver cells.
These folds are studded with small round bodies known as F1 particles or oxysomes.
Oxysomes elementary particles : Oxysomes elementary particles First oserved by Fernandez- Moran, 1962
Sessile oxysomes were found on c-face by PARSON
Lollipop shaped- 8.5 nm wide particles.
3- parts a round head piece or F -1 subunit-110 Å, joined by a short stalk (F 5 – F 6 -50 Å) to the base piece or F 1 –subunit 80-100Å, located in the inner membrane.
1,00,000 to 10,00,000 oxysomes in single mito.
ATPase in HEAD SUBUNIT- concerned with ATP synthesis.made up of five subunits.
Matrix : Matrix The space enclosed by the inner membrane.
contains about 2/3 of the total protein in a mitochondrion
is important in the production of ATP along with inner membrane
contains a highly-concentrated mixture of hundreds of enzymes, special mitochondrial 70 S ribosomes, tRNA, and several copies of the mitochondrial circular DNA genome, calcium and magnesium ions
Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle.
A published human mitochondrial DNA sequence revealed 16,569 base pairs encoding 37 total genes: 22 tRNA, 2 rRNA, and 13 peptide genes.
Functions : Functions Recently it has been shown that plant mitochondria can produce a limited amount of ATP without oxygen by using the alternate substrate nitrite
Intermediates for the synthesis of chlorophyll, cytochromes, steriods etc.
Some amino acids are also formed in mito.
It regulates calcium ion conc. in the cell by storing and releasing calcium as needed -"cytosolic buffers" for calcium------neurotransmitter release in nerve cells and release of hormones in endocrine cells--- Calcium signaling (including calcium-evoked apoptosis-cell programed death).
Matrix contains ENZYMES for the synthesis for the synthesis of fatty acids.
Autonomy : Autonomy Self replication and semi-autonomous.
For replication, they have- DNA, self transcribed- m RNA, t RNA, and r RNA, 70 S ribosomes- protein synthesizing mechanism, & synthesize membrane material and also structural proteins and enzymes.
However they can manufacture only few proteins and for others they depend on nuclear DNA.
Origin : Origin Derived from endosymbiotic , Lynn Margulis. prokaryotes,. This symbiotic relationship probably developed 1.7[-2 billion years ago.
A mitochondrion contains DNA, single, circular chromosome
The ribosomes coded for by the mitochondrial DNA are similar to those from bacteria in size and structure.
A few groups of unicellular eukaryotes lack mitochondria: the microsporidians, metamonads, and archamoebae. These groups appear as the most primitive eukaryotes on phylogenetic trees
Other useful information : Other useful information Unit membranes of mitochondria -60 Å wide
Peri-mitochondrial space-40-70 Å wide, coversion of pyruvic acid into acetyl Co A.
Mitoplast- mitochondrai when treated with detergent like- digitonin / lubrol , outer membrane is removed and it is now called mitoplast.
Enzymes α-ketoglutaric dehydrogenase & succinic dehydrogenase occur in mito matrix only.
S-value of mitoribosomes varies-80Sin higher plants, 70-80s in fungi & protists, 55-60s in animals.
In all probability mito arise from nuclear envelope by evagination.
Crista are found in animals, tubules in plants & both again in plants
Mito are rich in Mn, yellow in colour due to riboflavins