3 Organelles with single membranes
Cells can be disrupted by shear forces in a homogenizer and the components can then be separated by centrifugation.
Endo(sarco)plasmic reticulum
The endoplasmic reticulum (ER), or sarcoplasmic reticulum (SR) in muscle cells, is composed of flattened sacs and tubules (cisternae) of membrane within the cytoplasm and often forms concentric layers around the nucleus. It forms a continuation of the nuclear envelope such that the ER lumen is continuous with the periplasmic space of the nuclear envelope. This membrane structure may represent up to half of the total cell membrane in an actively secreting cell. The association of ribosomes with the ER allows regions of ‘rough’ ER to be distinguished from areas of smooth ER devoid of ribosomal contacts. Ribosomes associated with rough ER are involved in the synthesis of secretory, lysosomal and membrane proteins. Both rough and smooth ER are involved additionally in: protein glycosylation (Fig. 3.3.1
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