A mitochondrion is an organelle, a specialized structure found inside almost all eukaryotic cells. Eukaryotic cells contain a nucleus and membrane-bound organelles, like mitochondria. Mitochondria have been called the powerhouse of the cell because of their role in cellular respiration and energy production. Without mitochondria, we would not be able to properly use our energy and live.

Cellular respiration occurs when oxygen breaks down food molecules and generates energy (ATP). Check out the diagram below:

You might notice that cellular respiration is occurring primarily within the mitochondrion. It's important to note that cellular respiration is the means by which we use materials to create energy for our basic metabolic processes. Without cellular respiration, we would not be able to function and live; and yes, all living things utilize some form of cellular respiration, including plants that also rely upon photosynthesis.

Mitochondria are small membrane-bound organelles that are usually about 1 – 10 microns in length. 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 maximizes 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 synthesize proteins independently. It contains the enzymes necessary for transcription, as well as the transfer RNAs and ribosomes required for translation and protein formation.