mitochondria
Last reviewed 01/2018
A mitochondrion, plural mitochondria, is the cellular organelle involved with energy production. Situated within the cytoplasm, it has a double outer membrane and is rod-shaped or filamentous.
The outer membrane is permeable small molecules. The inner membrane is elaborately folded into projections, termed cristae, which point inwards. Within the inner membrane are a number of enzymes involved with the electron transport system of energy metabolism. Deep to the inner membrane is the mitochondrial matrix which contains:
- enzymes of the Kreb's cycle
- enzymes to oxidize free fatty acids
- DNA
- RNA
- ribosomal protein
- cation-binding proteins
The number and size of mitochondria per cell is generally proportional to energy requirements and is specific to cell type. Mature keratinocytes and erythrocytes do not possess mitochondria. Mitochondria also tend to accumulate around sites with a high energy requirement e.g. next to the brush border of absorptive epithelia.
The mitochondrion possesses its own DNA and is able to self-replicate. However, it cannot exist outside of the cell environment without proteins derived from nuclear DNA.