That type is known as "transitional" or "smooth."
The sequence KDEL marks proteins for retention in this structure. Chaperone proteins located in this structure fold newly created proteins. A specialized variety of this structure stores calcium ions and is found in smooth and striated muscle. That "sarcoplasmic" (sar-co-PLAZZ-mic) type of this organelle is in turn a subset of a type of this structure which is the location of carbohydrate and steroid metabolism. That type is known as "transitional" or "smooth." For 10 points, name this organelle, which also has a "rough" type that contains ribosomes (RYE-bo-soams).
The sequence KDEL marks proteins for retention in this structure.
{endoplasmic reticulum} [or {ER}; or {smooth endoplasmic reticulum}; or {rough endoplasmic}