Mitochondrial matrix
The cytosolic, intermembrane space, compartment has a water content of 3.8 μl/mg protein, while the mitochondrial matrix 0.8 μl/mg protein. It is not known how mitochondria maintain osmotic balance across the inner mitochondrial membrane, although the membrane contains aquaporins that are believed to be conduits for regulated water transport. Mitochondrial matrix has a pH of about 7.8. Mitochondrial DNA was discovered by Nash and Margit in 1963. One to many double stranded mainly circular DNA is present in mitochondrial matrix. Mitochondrial DNA is 1% of total DNA of a cell. It is rich in Guanine and Cytosine content. Mitochondria of mammals have 55s ribosomes.
Cheddar Man
The mitochondrial DNA of Cheddar Man was of haplogroup U5b1. Some 65% of western European Mesolithic hunter-gatherers had haplogroup U5; today it is widely distributed, at lower frequencies, across western Eurasia and northern Africa. In 1996, Bryan Sykes of the University of Oxford first sequenced the mitochondrial DNA from one of Cheddar Man's molars.