CELL ORGANELLES: bound ribosomes

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ALL CELLS / Animal Cell : nucleus / nucleolus / nuclear envelope / nuclear pore / centrioles / cell membrane / microtubule / smooth endoplasmic reticulum / rough endoplasmic reticulum / ribosomes / polysomes / lysosome / peroxisome / mitochondrion / Golgi /

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ORGANELLE DIAGRAM: RIBOSOMES: In this picture, ribosomes are the pale yellow bead-like objects that are attached to the exterior (cytoplasmic side) of the rough endoplasmic reticulum. These ribosomes are busy with protein synthesis. Stringing them together is messenger RNA which directs protein manufacture as it passes through the ribosomes. The growing proteins project into the cavity (lumen) of the rough ER. Other ribosomes are free in the cytoplasm.

Such membrane-bound ribosomes impart a beaded (rough) appearance to endoplasmic reticulum when it is inspected by an electron microscope.

SUMMARY

• name(s): bound ribosomes, attached ribosomes
• location: the outer (cytosol) surface of the rough endoplasmic reticulum.
• appearance: approximately spherical bodies often arranged in strings or spirals (because they are strung together by messenger RNA).
• size: about 25nm in diameter
• function: synthesis of proteins

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