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Enlargement of Figure 5a indicating that ribosomes are attached to
the cytosolic side of the transition zone of the ER. COP-II coats
presumably allow the ER membrane to accumulate protein cargo and to
evaginate (arrowheads) into a pit which will pinch off into
transition vesicles. These then fuse with the Golgi stack which in
paramecia consists of only two or three cisternae. Glycosylation of
the proteins may occur in the cisternae which may target the proteins
to lysosomes, to the plasma membrane, or to the endosomal system.
Paramecium does not have sialic acid as the terminal sugar of
its complex carbohydrate as part of its glycosylated proteins and
lipids. Bar = 0.1µm.
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