Mitochondrial Membrane: Anatomy and Functions | Biologic Oxidation

In this article we will discuss about the Anatomy and Functions of Mitochondrial Membrane.

Anatomy of Mitochondrial Membrane:

1. The outer membrane of mitochondria is permeable to most metabolites, but the inner membrane is selectively permeable.

2. The inner membrane has a matrix and the inner membrane is thrown into folds or cristae.

3. The presence of monoamine oxidase and a few other enzymes such as acyl-CoA synthetase, phospholipase A₂, glycerophos­phate acyltransferase, monoacyl glycero­phosphate acyltransferase is found in the outer membrane and the outer membrane may be removed by the treatment with digitonin.

4. Adenylate kinase is found in the inter-membrane space.

5. Cardiolipin is concentrated in the inner membrane where most of the lipid is phos­pholipid.

Functions of Mitochondrial Membrane:

1. The phosphorylating subunits responsi­ble for the production of ATP are scattered over the surface of the inner membrane. These subunits consist of several proteins collectively known as an F₁ subunit which project into the matrix. These F₁ subunits also contain the ATP synthetase. These subunits are attached, probably by a stalk, to a membrane protein subunit known as Fo which extends through the membrane.

2. One ATP molecule is formed from ADP and Pi when every proton pair passes through the F₀ – F₁ complex. Similar phosphorylating units are found inside the plasma membrane of bacteria but outside the membrane of chloroplasts.

3. Vesicles (Sub-mitochondrial particles) that are “inside-out” are formed on the inner mitochondrial membrane and, therefore, the phosphorylating units are located on the outside of the membrane.

4. The enzymes of the TCA cycle and (β-oxidation of fatty acids are found in the ma­trix to associate mechanisms for transport­ing ions and fatty and other organic acids as well as nucleotides across the inner membrane.

5. Succinate dehydrogenase is found on the inner surface of the inner mitochondrial membrane and it transports reducing equivalents in the respiratory chain at ubi­quinone (CoQ).

6. β-hydroxybutyrate dehydrogenase is also bound to the matrix side of the inner mi­tochondrial membrane.