Eye care in the community 5

The mitochondria are found in large numbers in most cells. Each mitochondrion consists of a solid outer membrane and an inner membrane with folds and within this a fluid containing matrix.

Mitochondria are small membrane-bound organelles that are usually about one to 10 microns in length (figure 1). They can be spherical or rod-shaped. The mitochondrion is enclosed by two membranes that separate it from the cytosol and the rest of the cell components. The membranes are lipid bilayers with proteins embedded within the layers. The inner membrane is folded to form cristae; this increases the surface area of the membrane and maximises cellular respiration output. The region between the two membranes is the intermembrane space. Inside the inner membrane is the mitochondrial matrix, and within the matrix there are ribosomes, other enzymes, and mitochondrial DNA. The mitochondrion is able to reproduce and synthesise proteins independently. It contains the enzymes necessary for transcription, as well as the transfer RNAs and ribosomes required for translation and protein formation.