The lumen of the ER is equivalent topologically to the
A) cytoplasm.
B) cytoplasmic face of the plasma membrane.
C) extracellular space.
D) nucleoplasm.

Question

Quizplus · Accepted Answer

The lumen of the endoplasmic reticulum (ER) is topologically equivalent to the extracellular space because molecules within the ER lumen do not directly mix with the cytosol; they are instead secreted or transported to the cell surface in a manner similar to how substances are handled in the extracellular space.

The Lumen of the ER Is Equivalent Topologically to the