Final answer:
The rough endoplasmic reticulum modifies proteins and synthesizes phospholipids, while the smooth endoplasmic reticulum synthesizes carbohydrates, lipids, and steroid hormones and also detoxifies drugs and stores calcium ions.
Step-by-step explanation:
The rough endoplasmic reticulum (RER) is studded with ribosomes and is involved in protein modification. It also synthesizes phospholipids used in cell membranes. On the other hand, the smooth endoplasmic reticulum (SER) synthesizes carbohydrates, lipids, and steroid hormones, detoxifies medications and poisons, and stores calcium ions.