To determine the incorrect statement about the Endoplasmic Reticulum (ER), let's evaluate each option:
- RER has ribosomes attached to ER: This statement is correct. The Rough Endoplasmic Reticulum (RER) is characterized by having ribosomes on its cytoplasmic surface, which gives it a "rough" appearance under a microscope.
- SER is devoid of ribosomes: This statement is correct. The Smooth Endoplasmic Reticulum (SER) lacks ribosomes, making its surface appear smooth.
- In prokaryotes only RER are present: This statement is incorrect. Prokaryotes do not have an Endoplasmic Reticulum. Both RER and SER are components of eukaryotic cells, not found in prokaryotes such as bacteria.
- SER are the sites for lipid synthesis: This statement is correct. The Smooth Endoplasmic Reticulum is involved in the synthesis of lipids and steroid hormones.
Thus, the statement that is incorrect regarding the Endoplasmic Reticulum is: In prokaryotes only RER are present.