Mitochondria are bean-shaped organelles that are found in the cytoplasm of almost all eukaryotic cells. They are often referred to as the "powerhouse of the cell" because they are responsible for producing most of the cell's energy in the form of adenosine triphosphate (ATP). Structure of Mitochondria Each mitochondrion is enclosed by two membranes: an outer membrane and an inner membrane. The outer membrane is smooth and permeable to most molecules, while the inner membrane is highly folded and contains many proteins that are involved in energy production. The space between the outer and inner membranes is called the intermembrane space. Inside the inner membrane is a fluid-filled matrix that contains mitochondrial DNA, ribosomes, and enzymes. The mitochondrial DNA is different from the DNA in the cell nucleus and encodes its own set of genes. These genes are essential for the production of mitochondrial proteins, which are involved in energy production, cell signaling, and other important cellular functions. How Mitochondria Work Mitochondria produce ATP through a process called oxidative phosphorylation. Oxidative phosphorylation is a complex process that involves the transfer of electrons from food molecules to oxygen. This process takes place in the electron transport chain, which is located in the inner mitochondrial membrane. The electron transport chain is made up of a series of protein complexes that pass electrons from one complex to the next. As the electrons are passed along the chain, they lose energy, which is used to pump protons across the inner mitochondrial membrane. This creates a proton gradient across the membrane, which drives the production of ATP. ATP is produced by a protein complex called ATP synthase. ATP synthase uses the energy from the proton gradient to synthesize ATP from ADP and inorganic phosphate. ATP is then transported out of the mitochondria and used by the cell to power its various activities. Other Functions of Mitochondria In addition to producing ATP, mitochondria also play a role in a number of other cellular processes, Mitochondria are essential organelles that are involved in a wide range of cellular processes. They play a particularly important role in energy production, but they also play a role in cell signaling, calcium homeostasis, iron metabolism, and detoxification. Mitochondrial diseases can cause a variety of symptoms, but there are treatments that can help to manage the symptoms.