EVERYDAY SCIENCE

Detailed explanation-1: -Membrane-bound ribosomes, attached to the cytosolic side of the ER membrane, are engaged in the synthesis of proteins that are being concurrently translocated into the ER. Free ribosomes, unattached to any membrane, synthesize all other proteins encoded by the nuclear genome.

Detailed explanation-2: -This rough endoplasmic reticulum (Rough ER) studded with protein-producing ribosomes is the site of synthesizing proteins destined to export out of the cell.

Detailed explanation-3: -The site of synthesis of proteins for export is the endoplasmic reticulum. All protein synthesis starts in the nucleus with transcription.

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: -Extracellular proteins are exported from the cell using the endoplasmic reticulum/Golgi-dependent secretory pathway, which involves the rough endoplasmic reticulum, Golgi apparatus (cis face and trans face), and the plasma membrane.