Mitochondria 3d render

The mitochondrion is the organelle responsible for producing ATP, the cell's energy currency, and has its own DNA.

About this subject

Mitochondria are double-membrane organelles found in most eukaryotes. The outer membrane is smooth, while the inner membrane folds into cristae, increasing surface area for chemical reactions. The space between membranes is the intermembrane space, and the interior is the mitochondrial matrix, where the Krebs cycle and fatty acid oxidation occur.

The primary function of mitochondria is ATP production via oxidative phosphorylation. During cellular respiration, pyruvate from glycolysis is converted to acetyl-CoA and enters the Krebs cycle, generating NADH and FADH2. These electron carriers feed the electron transport chain in the inner membrane, creating a proton gradient that drives ATP synthase. This process, known as chemiosmosis, produces the majority of cellular ATP.

Mitochondria are unique for containing their own circular genome, similar to bacteria, supporting the endosymbiotic theory that they evolved from endosymbiotic prokaryotes. Mitochondrial DNA (mtDNA) is inherited solely from the mother and encodes only 13 proteins, plus RNAs. Mutations in mtDNA can lead to mitochondrial diseases such as Leber hereditary optic neuropathy. Besides energy production, mitochondria are involved in cell signaling, differentiation, and apoptosis, releasing cytochrome c to initiate programmed cell death.

Frequently Asked Questions

How many mitochondria are in a typical cell?

The number varies by cell type. Muscle and liver cells can contain hundreds to thousands of mitochondria, while mature red blood cells have few or none.

Why do mitochondria have their own DNA?

Mitochondrial DNA is a remnant of the bacterial origin of mitochondria, as per the endosymbiotic theory. It encodes essential proteins for cellular respiration that are not supplied by the nucleus.

What is oxidative phosphorylation?

It is the process of ATP production in mitochondria, using energy from nutrient oxidation to pump protons across the inner membrane, creating a gradient that drives ATP synthase.