Starting at a ribosome and ending at the plasma membrane tra

Starting at a ribosome and ending at the plasma membrane, trace the path of a newly synthesized protein that will be secreted by the cell.

Solution

Proteins those are synthesized and stored in the secretory pathway. Although all cytosolic ribosomes are functionally equivalent, membrane-attached and membraneunattached ribosomes synthesize different classes of proteins, depending on a signal sequence in the protein itself. Newly made secretory proteins are localized to the lumen of the rough ER. All mammalian cells continuously secrete certain proteins, such as those in the extracellular matrix. Certain cell types store proteins such as hormones and digestive enzymes in secretory vesicles, awaiting a neural or hormonal signal that triggers an elevation in cytosolic Ca2+ and then protein secretion. Proteins destined to be secreted move through the secretory pathway in the following order: rough ER ER-to-Golgi transport vesicles Golgi cisternae secretory or transport vesicles cell surface (exocytosis).Small transport vesicles bud off from the ER and fuse to form the cis-Golgi reticulum. By cisternal migration, cis-Golgi vesicles with their luminal protein cargo move through the Golgi complex to the trans-Golgi reticulum. Proteins are retrieved from the cis-Golgi to the ER and also from later Golgi cisternae to earlier ones by small retrograde transport vesicles. Plasma-membrane glycoproteins follow the same maturation pathway as continuously secreted proteins.Both secreted and integral membrane proteins undergo various modifications as they mature in the secretory pathway.