mitochondria

fig : Mitochondria

Number of mitochondria depends upon physiological activity of cell.

• One in Microasterias, Chlorella fusca (alga)
• All the mitochondria present in a cell are collectively called chondriome.
• Usually plant cells have fewer mitochondria as compared to animal cell.
• In higher animals maximum mitochondria are found in flight muscles of birds.
• Mitochondria are differ in size and shape and can make its shape sausage or cylindrical.
• Diameter 0.2-1.0 um (average 0.5 um), length 1.0-4.1 uum

Mitochondria is also named as - 

• Power house of cell or ATP-mill in cell
• Cell within cell
• Most busy and active organelle in cell Semi autonomous cell organelle,
• Endosymbionts of cell

STRUCTURE

• Mitochondria unless specifically stained are not easily visible under the microscope. Mitochondria are stained by Janus green B.
• Mitochondria is covered by double unit membrane, the outer membrane is smooth and inner one folds into several cristae. Outer membrane has more phospholipids (Phosphatidyl choline) and cholesterol as compared to inner membrane. Phospholipid in inner membrane is mainly phosphatidyl glycerol and Inner membrane have more protein
• The outer membrane and the inner membrane dividing its lumen distinctly into two aqueous.compartments.ie.. the outer compartment and the inner compartment. The inner compartment filled with a dense homogenous substance is called the matrix. The outer membrane forms the continuous limiting boundary of the organelle
• The two membranes have their own specific enzymes associated with the mitochondrial function
• Both membrane are separated by a space called peri mitochondrial (Intermembrane) space
• Inner membrane is folded into a number of finger like cristae.
•  In metabolically active mitochondria number of cristae is higher Many electron carrier cytochromes are arranged in a definite sequence in Inner membrane of mitochondria, which forms Electron transport system (ETS).
• Inner membrane is studded with pin head particles called oxysomes or elementary particles on particles or ATP Synthase. These particles first described by Fernandez Moran.
• Head of Oxysomes or F, is concerned with Oxidative phosphorylation (formation of ATP by energy of oxidation).
•  Mitochondrial matrix have enzyme for Krebs cycle (Aerobic respiration). Beside these enzymes matrix have a complete protein synthesis apparatus (Ribosome (70-s), DNA, few RNA's & enzymes) so mitochondria called as semi autonomous cell organelles.
• Single double stranded and circular naked DNA present in mitochondrial matrix.
•  Mitochondrial DNA is 1% of total DNA in a cell. It is rich in GC content
• Mitochondrial DNA can code the synthesis of some types of proteins. Rest of the proteins and enzymes of mitochondria are synthesized under the control of nuclear genes.
• Enzymes for replication and transcription of DNA like DNA- polymerase and RNA- polymerase are found in mitochondrial matrix.

FUNCTION OF MITOCHONDRIA:

Mitochondria are site of aerobic respiration and ATP production.

 

Biogenesis of mitochondria -

• New mitochondria arise from division of pre-existing mitochondria (Mitochondria divide By binary fission
• Endosymbiotic origin from prokaryotic cells.
• Type of DNA (DNA sequences, double stranded, circular, G-C rich).
• Type of ribosome (70s).
• Divide by binary fission.