I believe it is said in meme culture that the mitochondria are the powerhouses of the cell. I’m not going to pretend to know why that is a meme, but there is some truth in it. The main function of the mitochondria is to carry out aerobic respiration (except the first stage) which produces adenosine triphosphate (ATP). ATP can be hydrolysed to release energy. Energy is required for many processes that take place inside cells, for example active transport of molecules across the cell-surface membrane.
The space between the membranes is, again unoriginally, called the intermembrane space (inter = between). The very middle, inside the membranes, is called the matrix but is nothing to do with Keanu Reeves. Instead it contains enzymes needed to carry out some stages of aerobic respiration.
Mitochondria also contain their own circular DNA and ribosomes. This is thought to be a remnant of when they were primitive prokaryotic organisms which evolved to live inside other cells. However their genome is still important for their function, and the ribosomes allow translation of polypeptides encoded by the mitochondrial genome.
The number of mitochondria in one cell depends on the type of cell. Some cells use more energy than others and need to produce a lot of ATP. For example, muscle cells need lots of energy to contract, so they will have many mitochondria to keep up with ATP demand.
Summary
- Mitochondria carry out aerobic respiration to produce ATP – an immediate source of energy.
- They have a double membrane and the inner membrane is folded – the folds are called cristae.
- The middle area is called the matrix and contains enzymes.
- Only eukaryotic cells have mitochondria.
- The number depends on the energy demand of the cell type.
