Cell nucleus membranes. Coloured freeze-fracture transmission electron micrograph (TEM) of part of the nuclear membrane of a liver cell. Fracture- faces of both inner (top, blue) and outer (centre, brown) membranes of the nucleus are seen. Rounded pores are seen on these membranes, which allow large molecules to pass out of the nucleus into the cytoplasm (bottom, blue). A double membrane encloses the nucleus to keep the cell's genetic material in a single unit. Tiny intramembranous particles (IMP's) make the membranes look rough and speckled. This cell specimen was frozen, and then fractured to reveal its internal surfaces. Magnification: x23,200 at 6x7cm size. Magnification: x80,000 at 10x8 inch size.
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