Protein synthesis can occur either on free ribosomes (polysomes) in the cytoplasm or on the rough endoplasmic reticulum (RER). Proteins made on free ribosomes become soluble in the cytosol. They include cytoskeletal proteins and cytosolic enzymes. Proteins made on the RER have three fates: 

1. They can be soluble within the lumen of the RER. This occurs if the signal sequence is clipped and there is no stop-transfer (anchor) sequence.

2. They can have a stop-transfer (anchor) sequence that embeds them in the RER membrane. These proteins will be integral membrane proteins.

3. They can have a phospholipid covalently attached that will anchor them to the membrane.