Your assignment is to prepare and submit a paper on 1. describe briefly the roles of the different parts of the eukaryotic cells endomembrane system in the production and excretion of proteins. Endomembrane of A Eukaryotic Cell Key Words: Eukaryotic cell, Endomembrane system, Golgi apparatus, Endoplasmic reticulum, Sulfation, Glycosylation, Phosphorylation, extracellular matrix,
A eukaryotic cell has a membrane that encloses its nucleus together with other organells (Starr, Evers & Starr, 2010).This cells have a number of membrane bound components together referred as endomembrane system (Starr, Evers & Starr, 2010). The endomembrane consists of the endoplasmic reticulum, nuclear envelope, Golgi apparatus, lysosome and plasma membrane (Eroschenko & Fiore, 2013).
The rough endoplasmic reticulum avails adequate surface area meant to accommodate extra ribosomes, which are sites for protein synthesis (Gupta, 2009). Proteins destined for various parts of the cell first enter the endoplasmic reticulum (Gupta, 2009). The endoplasmic reticulum ensures quality control of the proteins and at the same time provides a point of accumulation of storage proteins. The reticulum is then mandated with the duty of transiting already made proteins to the Golgi apparatus (Gupta, 2009). The nuclear envelope also has some ribosomes and is responsible for newly made Glyco- proteins. The Golgi apparatus undertakes the function of making, modifying as well as binding proteins (Eroschenko & Fiore, 2013). This is due to the nature of its enzymes’ modification, hence known for carrying out for sulfation, glycosylation, and phosphorylation of the proteins (Karp, 2010). Some modification activities act as signals directing proteins to their respective locations, which are plasma membrane, lysosome, or for secretion (Eroschenko & Fiore, 2013). Lysosomes contain a variety of digestive enzymes and are responsible for digestion of proteins. In plants, vacuoles correspond to the lysosomes of animals (Karp, 2010). Proteins that move to the plasma membrane form the lipid bilayer. They act as membrane proteins besides having varied roles in their respective locations in the cell (Eroschenko & Fiore, 2013). They regulate chemical reactions in the cell as well as uptake of molecules. They also act as carriers of molecules across the membrane and provide anchorage too. From the Golgi apparatus, there is a constitutive secretory pathway used to export the secretory proteins continuously to the extracellular matrix (Karp, 2010). Some cells however have a guarded secretory pathway. Some cells secrete regulatory proteins like hormones whereas others secrete digestive enzymes, anti -bodies or mucus (Karp, 2010).
Eroschenko, V. P., & Fiore, M. S. H. (2013). diFiores atlas of histology with functional correlations. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
Gupta, P. K. (2009). Cell and molecular biology. Meerut, India: Rastogi Publications.
Karp, G. (2010). Cell and molecular biology: Concepts and experiments. Hoboken, NJ: John Wiley.
Starr, C., Evers, C. A., & Starr, L. (2010). Biology: Today and tomorrow: with physiology. Australia: Brooks/Cole Cengage Learning.