Mitochondrion – Power house of the cell
The mitochondrion is cylindrical in shape and has two membranes: an outer surrounding membrane of 60Å thick and is regular in outline ; an inner membrane which forms folds called cristae. It is on the cristae that chemical reactions occur. Since the mitochondria synthesize energy−rich compounds (ATP), they are known as power house of the cell. This process is called aerobic respiration and is the reason animals breathe oxygen. Mitochondria are sites of cell respiration: sugars and fats are oxidized to produce energy which is then stored. Mitochondrial matrix also contains enzymes for oxidation of aminoacids and fatty acids and the enzymes of krebs cycle, the enzymes of electron transport and oxidative phosphorylation located in the cristae membranes to produce ATP that provides the necessary energy for various biochemical reactions of the cell. These are otherwise called semi-autonomous organelles as it has its own circular DNA, ribosomes and reproduces independently of the cell in which it is found. Hence play a role in heredity by the way of cytoplasmic inheritance.
The mitochondria (singular: mitochondrion) are tiny bodies of varying shapes (cylindrical, rod‐shaped, spherical) and sizes, distributed in the cytoplasm. Mitochondria are bounded by a double membrane.
Each of these membranes is a phospholipid bilayer with embedded proteins. The outermost membrane is smooth while the inner membrane has many folds. These folds are called cristae. The folds enhance the "productivity" of cellular respiration by increasing the available surface area. Cristae are studded with small rounded bodies known as F1 particles or oxysomes.
The interior cavity of the mitochondria is filled with a proteinaceous (gel‐like) matrix which contains a few small‐sized ribosomes, a circular DNA molecule and phosphate granules. Mitochondria are absent in bacteria and the red blood cells of mammals.
Mitochondria are sites of cellular respiration, which ultimately generates fuel for the cell’s activities. They use molecular oxygen from air to oxidize the carbohydrates and fats (lipids) present in the cell to carbon dioxide and water vapor.
Oxidation releases energy, a portion of which is used to form ATP (the organic compound adenosine triphosphate). Since the mitochondria synthesize energy‐rich compounds (ATP), they are known as power house of the cell. This process is called aerobic respiration and is the reason animals breathe oxygen. ATP is the chemical energy "currency" of the cell that powers the cell’s metabolic activities.
The body of organism uses energy stored in ATP for synthesis of chemical compounds (e.g., DNA replication, transcription of RNAs, and synthesis of proteins, carbohydrates and lipids) and for mechanical work, such as contraction of muscles (for movement, locomotion, peristalsis), movement of cilia and flagella, conduction of nerve impulse and production of heat, electricity (e.g., electric eel), and light (e.g., fire flies).
The mitochondrion is different from most other organelles because it has its own circular DNA (similar to the DNA of prokaryotes) and reproduces independently of the cell in which it is found. So, they are regarded as semi-autonomous organelles.
All living cells have mitochondria. Some cells have more mitochondria than others. The number of mitochondria in a cell varies widely by organism and tissue type. Your fat cells have many mitochondria because they store a lot of energy. Muscle cells have many mitochondria, which allows them to respond quickly to the need for doing work.