Final answer:
The smooth endoplasmic reticulum (SER) is responsible for the synthesis of oils, phospholipids, and steroids. The nucleus and mitochondria have double phospholipid bilayers and their own DNA, with mitochondria being the powerhouse of the cell. Ribosomes, produced in the nucleolus, are critical for protein synthesis in all cells.
The organelle primarily involved in the synthesis of oils, phospholipids, and steroids is the smooth endoplasmic reticulum (SER). This organelle engages in the production and metabolism of fats and steroid hormones, which are essential for the structure and function of biological membranes, among other critical cellular functions. Unlike the rough ER, the SER lacks ribosomes on its surface and is hence smooth in appearance.
For example, cells that have a high concentration of smooth endoplasmic reticulum are those that synthesize steroid hormones, like certain endocrine cells. Meanwhile, ribosomes, whether free in the cytoplasm or attached to the rough ER, are essential for protein synthesis. The nucleolus within the nucleus is where the RNA components of ribosomes are synthesized before assembly into complete ribosomes in the cytoplasm.
In terms of cellular organization and endosymbiotic relationships, organelles like the nucleus and mitochondria are distinct in that they have double membranes and their own DNA. The nucleus is surrounded by a double phospholipid bilayer known as the nuclear envelope, whereas mitochondria are double-membrane organelles with their own DNA and are involved in energy production through cellular respiration.