Reduced coenzymes such as NADH and NADPH do not permeate the inner membrane of the mitochondrion to any significant extent. However, reduced pyridine nucleotides are known to be produced in a number of reactions in the cytosol (the reduction of NAD+ at the glyceraldehyde step in glycolysis is an important example) and the re-oxidation of NADH occurs via the mitochondrion. [...]
A consistent observation made for plasma membranes that was not explained by the bimolecular lipid leaflet model was the very low surface tension of the cell membrane. In 1935, J. F. Danielli and E. N. Harvey proposed that oil droplets and other lipid inclusions in cells were bounded at their surfaces by an organized layer of the lipid and a [...]
The fluid-mosaic model of membrane structure is beautifully supported by visual evidence provided when freeze-fractured membranes are examined with the transmission electron microscope. D. Branton, who pioneered this field, showed that membranes rapidly frozen at the temperature of liquid nitrogen and cut or chipped with a microtome blade readily fracture along specific planes. When the plane of the fracture intersects [...]