DR KARI LOUNATMAA / SCIENCE PHOTO LIBRARY DR KARI LOUNATMAA / SCIENCE PHOTO LIBRARY
Cell nucleus membrane. Coloured freeze-fracture transmission electron micrograph (TEM) of part of the nuclear membrane of a liver cell. The concave fracture-face of the outer membrane of a nucleus is seen. This membrane reveals rounded nuclear pores. Pores in the membrane allow large molecules to pass out of the nucleus into the cytoplasm to communicate with other parts of the cell. A double membrane encloses the nucleus to keep the cell's genetic material in a single unit. Around the nucleus can be seen cytoplasm with cell organelles (at lower frame). This cell specimen was frozen, then fractured to reveal its internal surfaces. Magnification: x25,000 at 5x6 inch size.
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