Mitochondria

Organelle Project: Mitochondria
Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system which takes in nutrients, breaks them down, and creates energy rich molecules for the cell. The biochemical processes of the cell are known as cellular respiration. Many of the reactions involved in cellular respiration happen in the mitochondria. Mitochondria are the working organelles that keep the cell full of energy.

The outer membrane is a phospholipid bilayer, containing protein structures called porins which render it permeable to molecules of about 10 kilodaltons or less (the size of the smallest proteins). Ions, nutrient molecules, ATP, ADP, etc. can pass through the outer membrane with ease.The inner membrane is freely permeable only to oxygen, carbon dioxide, and water. The wrinkles, or folds, are organized into lamillae (layers), called the cristae. The cristae greatly increase the total surface area of the inner membrane.The membranes create two compartments. The intermembrane space, as implied, is the region between the inner and outer membranes. It has an important role in the primary function of mitochondria, which is oxidative phosphorylation.The matrix contains the enzymes that are responsible for the citric acid cycle reactions. The matrix also contains dissolved oxygen, water, carbon dioxide, the recyclable intermediates that serve as energy shuttles, and much more. Since diffusion is a very slow process and the folds of the cristae make no part of the matrix is far from the inner membrane, the matrix components can diffuse to inner membrane complexes and transport proteins within a relatively short time. Mitochondria are found in nearly all eukaryotic cells

Symbiogenesis, or endosymbiotic theory, is an evolutionary theory that explains the origin of eukaryotic cells from prokaryotes. It states that several key organelles of eukaryotes originated as a symbiosis between separate single-celled organisms. According to this theory, mitochondria, plastids (chloroplasts), and possibly other organelles representing formerly free-living bacteria were taken inside another cell as an endosymbiont around 1.5 billion years ago. Molecular and biochemical evidence suggest that mitochondria developed from proteobacteria (in particular, Rickettsiales, the SAR11 clade, or close relatives) and chloroplasts from cyanobacteria (in particular, nitrogen-fixing filamentous cyanobacteria). In 1904, Friedrich Meves made the first recorded observation of mitochondria in plants (Nymphaea alba). Mitochondria are too small to be seen from a light microscope. Although most of a cell's DNA is contained in the cell nucleus, the mitochondrion has its own independent genome. Mitochondrial diseases result from failures of the mitochondria, specialized compartments present in every cell of the body except red blood cells. Mitochondria are responsible for creating more than 90% of the energy needed by the body to sustain life and support growth. When they fail, less energy is generated within the cell. Cell injury and even cell death may follow. If this process is repeated throughout the body, whole systems begin to fail, and the life of the person in whom this is happening is jeopardized. The disease primarily affects children, but adult onset is becoming more and more common. Diseases of the mitochondria appear to cause the most damage to cells of the brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems. Depending on which cells are affected, symptoms may include loss of motor control, muscle weakness and pain, gastro-intestinal disorders and swallowing difficulties, poor growth, cardiac disease, liver disease, diabetes, respiratory complications, seizures, visual/hearing problems, lactic acidosis, developmental delays and susceptibility to infection

Most eukaryotic cells, those that contain nuclei, also contain mitochondria, but there are exceptions to this rule. Some parasitic protists, for example, take energy from their hosts and do not have mitochondria. In humans, mature red blood cells, or erythrocytes, lack mitochondria as well.No bacteria contain mitochondria. The endosymbiotic hypothesis proposes that mitochondria are the descendants of ancient bacteria that were engulfed by other cells and lost their ability to function outside their new hosts. Bacteria instead generates energy through different types of oxidation such as respiration, in which oxygen serves as the final electron acceptor, and fermentation, in which another organic compound fills that role