Mitochondrion: Components, Origin, Functions and Observation Techniques
In plant cell biology, the mitochondrion is an organelle that is found in nearly every eukaryotic organism. Shaped like a rod and enclosed by a double membrane (also called the phospholipids bi-layer), mitochondrion or its plural form, mitochondria, are sometimes referred to as the cell’s power plants because they are the source of the plant’s chemical energy. Mitochondria, which comes from the Greek words ‘mitos’ meaning thread and ‘khondrion’ meaning granule, contain the enzymes responsible for converting oxygen and carbohydrate, protein and fat metabolism products into ATP or adenosine triphosphate. ATP is the energy source that helps the cell perform its functions.
Components of the mitochondria
The mitochondria are considerably larger than many of the organelles contained within a plant cell. In fact, they are the second largest of the organelles that carry their own unique genetic material. The number of mitochondria that a single plant cell can contain varies, although cells that require higher levels of metabolic requirements typically have more. A mitochondrion measures about 5-10 micrometers long and about 0.5-1.0 micrometer wide. The outer membrane is smooth while the second, inner membrane is highly folded. The projections in this membrane are called cristae.
Most of the ATP that a mitochondrion will produce is found on the inner membrane, which is the ideal space for storage because of its surface area. Due to the fact that a mitochondrion has two membranes, it actually has three other compartments – 1) the intermembrane, which divides the inner and outer membranes, 2) the matrix, which is a liquid-filled compartment that contains enzymes that are necessary for aerobic respiration and 3) the folded membrane or cristae space where ATP is synthesized. The cristae also contain enzymes and transport proteins. These proteins carry molecules to the matrix after they are filtered by the inner membrane. Although a cell’s DNA is found mostly in the nucleus, each mitochondrion possesses its own genetic material, so it is capable of producing its own proteins and RNAs.
Mitochondria are not evenly distributed within the plant cell’s cytoplasm. Instead, they have been shown to clump together. They also exhibit evidence of a dynamic structure, capable of shifting positions and changing shape – from spherical to oval to bean-shaped to worm-like. Despite their common functions across plant species, mitochondria do not always appear in the same shape or size.
How mitochondria are formed
Mitochondria are formed when other mitochondria divide, which makes them acceptable as originating from endosymbiotic prokaryotes, primitive cells that do not contain a nucleus. Mitochondiral DNA and ribosomes are similar to that of prokaryotes. Since mitochondria have their own set of DNA, they can only develop through mitochondrial fission.
