If endoplasmic reticulum are membranes attached structures in the cytoplasm where proteins are made, then endoplasmic reticulum are what attached to structures in the cytoplasm where proteins are made?

Answer choices:
- recycling
 - allow growth
 - membranes
 - organ
 - layers of fat
 - more abundant
 - epidermal
 - Most plants

 

   membranes       