As you organize the outline you are going to use please use the following 4subti

Question

As you organize the outline you are going to use please use the following 4subtitles/categories I provide below. <- Divide your answers into these categories.  In a bullet/outline form simply name the component (RNA, protein, membrane etc.) used, in the order used, and where appropriate add a brief descriptor of that component. <- this should take no more than 1 line. Explain what happens at the category AND how the new lipid and protein transit to the next category again using a simple bullet/outline form.   The categories are:

A. Before ER

B. At the ER and how it transports to the Golgi

C. At the Golgi and how it transports to the plasma membrane.

D. At the Plasma Membrane

Effectively you are starting with an mRNA in the cytoplasm and processing it all the way through Constitutive and/or Regulative exocytosis. Be sure to include where new lipids are synthesized and how they move with the protein. Don't forget to include the recycling of components when they occur.

Explanation / Answer

Answer)

Two major cellular pathways shuttle material outward and inward. In the exocytic pathway, proteins synthesized in the cytoplasm are translocated into the endoplasmic reticulum (ER). Rough ER is the site of synthesis of all secreted proteins, and resident proteins for all compartments connected by vesicular transport. The ER is also the site where synthesis of most of the lipids in the cells begins. From the ER, membranous vesicles shuttle cargo to the Golgi apparatus. ER-derived cargo enters the Golgi in its cis cisterna, and moves through the medial and trans cisternae. In the trans Golgi, proteins destined for secretion or to be presented on the PM are packed into secretory vesicles that subsequently fuse with the PM. This fusion occurs either constitutively or, as in the case of regulated secretion, in response to an external signal. The Golgi apparatus is the major sorting compartment of the cell because in the Golgi cargo is sorted not only to the PM for constitutive and regulated secretion, but also to endosomes and lysosomes, or back to the ER.

In the endocytic pathway, proteins and membrane are internalized from the cell environment via a set of endosomes, early and late, to the lysosome . The lysosome is a major degradation site for both internalized and cellular proteins. Thus, cellular proteins can get to lysosomes either from the PM via the endocytic pathway or from the cytoplasm via the autophagy and the cytoplasm-to-vacuole targeting (CVT) pathways.

In addition, there is cross-talk between the exocytic and endocytic pathways. First, endosomal and lysosomal resident proteins and enzymes are shuttled from the ER via the Golgi to endosomes and lysosomes.vSecond, in polarized cells, proteins can be moved between two different environments, from one side of the cell to the other, via the transcytotic pathway. Lastly, macromolecules can be released from cells in small vesicles called exosomes by fusion of late endosomes, also known as multivesicular bodies (MVBs), with the PM..

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