LIFE SCIENCE

Detailed explanation-1: -Proteins are assembled at organelles called ribosomes. When proteins are destined to be part of the cell membrane or exported from the cell, the ribosomes assembling them attach to the endoplasmic reticulum, giving it a rough appearance.

Detailed explanation-2: -Ribosomes are the sites in a cell in which protein synthesis takes place.

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: -Sorting and Export of Proteins at the Endoplasmic Reticulum.