Mitochondria - Structure and isolation of mitochondrial Component

MITOCHONDRIA -STRUCTURE ORGANIZATION -ISOLATION OF MITOCHONDRIAL COMPONENTS 

George Palade published the first high resolution electron micrographs of Mitochondria. The Mitochondria, as an organelle exhibits a complex internal architecture. It is encompassed by too membranes-an outer mitochondrial membrane and inner mitochondrial membrane. Outer member define the external boundaries of the organelle and inner mitochondrial membrane exhibits numerous folds known as aristae that projects into the mitochondrial interior.

The detailed structure of mitochondria is shown in fig.1

Inner mitochondrial membrane is convoluted, the folds consisting of double membranes and called cristae(animals) & tubule or microvilli in plants. The fine structure of mitochondria can change in different cells of a tissue, at different stages of development the aristae may be simple or branched forming a complex network.

Attached to M-face [matrix facing] of Inner membrane are repeated units of stalked particles called elementary particles or inner membrane subunits or oxyosome. These particles are 8.5mm (85°A) in diameter and are regularly spaced at intervals of 10nm on the inner surface of these membrane.

The outer and inner mitochondrial membrane provider the mitochondria into two district compartments the inter membrane spaces located between outer and inner membrane and mitochondrial matrix. When is enclosed by the inner membrane space.

ISOLATION OF MITOCHONDRIAL COMPONENTS

The first successful technique for separating inner and outer membrane developed by Donald Parson. In this procedure mitochondria are placed in a hypotonic solutions  exposed to the detergent digitonion until the outer membrane ruptures, releasing the contents of the inter membrane space into solution. The inner membrane, outer membranes and components of inter membrane space are then separated by centrifugation. Isolated inner and outer membrane can be readily distinguished from each other by electron microscopy. Outer membrane book like empty sacs and inner membranes from vesicles called mitoplast containing matrix material within. Mitoplast can be further fractioned into inner membrane and matrix component by treating with detergent Lubrol. Lubrol distrups inner membrane into small inner membrane vesicles containing F₁ particles. Biochemical studies of isolated fraction. provides important information regarding the location of various metabolic activities of  the mitochondria.

Function

·         Outer membrane of Mitochondria is permeable and contains enzymes involved in lipid metabolism.

·         It contains monoamine oxidase enzyme Fatty acyl Co-A synthetase glycerolphosphatase acyl transfrase & Porin.

·         Inner Mitochondrial is the main site of Mitochondrial ATP formation and it is semi permeable in matrix  .

·         Mitochondrial matrix contains all of the enzymes of Kerb’s cycle.

·         Inner Mitochondrial membrane is also the site of several enzymatic pathways that are not directly related to energy metabolism e.g. involves in the synthesis of steroid harmones.