AP BIOLOGY

Detailed explanation-1: -The ribosome that is synthesizing the protein is directly attached to the ER membrane. These membrane-bound ribosomes coat the surface of the ER, creating regions termed rough endoplasmic reticulum, or rough ER (Figure 12-36A).

Detailed explanation-2: -The rough endoplasmic reticulum (RER) is so named for the appearance of its outer surface, which is studded with protein-synthesizing particles known as ribosomes.

Detailed explanation-3: -The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins.

Detailed explanation-4: -Proteins synthesized by the rough ER include the prominent milk protein casein, and whey proteins. These proteins are packaged into secretory vesicles or large micelles and travel through the Golgi network before fusing with the plasma membrane, releasing their contents into milk ducts.

Detailed explanation-5: -Plasma membrane and lysosomal proteins also travel from the rough ER to the Golgi and then to their final destinations. Still other proteins travel through the initial steps of the secretory pathway but are then retained and function within either the ER or the Golgi apparatus.