Inside the Cell Gogli Body Study Guide.pdf

Last edited: 2/24/2023 GOLGI APPARATUS STRUCTURE & FUNCTION Golgi Apparatus Structure & Function Medical Editors: Jan Camille Santico OUTLINE I) STRUCTURE...

Last edited: 2/24/2023 GOLGI APPARATUS STRUCTURE & FUNCTION Golgi Apparatus Structure & Function Medical Editors: Jan Camille Santico OUTLINE I) STRUCTURE II) FUNCTION (A) CIS GOLGI (A) PROTEIN MODIFICATION (B) LUMEN (B) PROTEIN RECYCLING (C) TRANS GOLGI (C) PROTEIN SORTING (D) LYSOSOMES III) REVIEW QUESTIONS IV) REFERENCES I) STRUCTURE The Golgi apparatus is a cell organelle with a folded/convoluted membrane that is made of a phospholipid bilayer It has two distinct functional sides or faces: o Cis Golgi o Trans Golgi The Golgi Apparatus From Textbook OpenStax Anatomy and Physiology (2016) (A) CIS GOLGI (C) TRANS GOLGI The cis Golgi is the convex side which faces the The trans-Golgi is the concave side that faces the cell rough endoplasmic reticulum (RER) membrane Proteins synthesized in the RER are transported via After proteins undergo posttranslational modifications vesicles, which are membrane-enclosed carriers that within the lumen, they are once again enclosed in bud off the RER membrane vesicles and are either: o The vesicles contain COP-II proteins, which direct o Brought to the cell membrane the vesicles from the RER towards the cis Golgi o Fused with lysosomes (anterograde) (D) LYSOSOMES Sometimes, vesicles bud off from the cis Golgi and move back towards the RER Lysosomes are the “garbage collectors” of the cell o These vesicles contain COP-I proteins, which They contain enzymes that break down damaged or direct the vesicles from the cis Golgi to the RER worn-out cellular debris (retrograde) (B) LUMEN The lumen of the Golgi apparatus is where the posttranslational modifications of proteins occur These modifications include folding the proteins into “usable shapes” and attaching additional molecules (e.g., lipids, carbohydrates) in order to turn the proteins into forms that the cell can use Cisternal progression (movement of proteins from the cis-face to the trans-face) allows sequential processing of newly synthesized proteins Golgi Apparatus Structure & Function CELL BIOLOGY: Note #14. 1 of 3  II) FUNCTION The Golgi apparatus or complex functions as a factory in which proteins received from the RER are further processed and sorted for transport to their eventual destinations (Cooper, 2000) Overview: Inside the nucleus is DNA, which can be transcribed into mRNA mRNA leaves the nucleus to bind to ribosomes in the RER From there, the ribosomes facilitate the translation of mRNA into proteins The proteins undergo n-linked glycosylation within the RER (an oligosaccharide is added onto asparagine)  Asparagine has an amino group that links to the oligosaccharide The protein is then packaged into vesicles and directed toward the cis Golgi The vesicles fuse with the membrane of the cis Golgi and release their contents into the lumen The proteins undergo posttranslational modification within the lumen (A) PROTEIN MODIFICATION (C) PROTEIN SORTING The Golgi lumen contains various enzymes which The Golgi apparatus packs proteins and tags them for facilitate protein modification a specific location At the end of the process, there is a fully packaged o Lysosomes modified protein with a specific destination o Membrane protein o Secretion (1) N-linked glycosylation They attach special proteins such as clathrin (coat Sugar residues are trimmed, making the protein active the vesicles and direct the destination of proteins) and more specific (2) O-linked glycosylation A sugar residue is added to a hydroxy (-OH) group in the protein Two amino acids can be added to make it active: o Serine o Threonine (3) Phosphorylation Sugar residues have “mannose” at the end When mannose is phosphorylated, liposomal enzymes are activated, and the protein is tagged for lysosomal degradation (B) PROTEIN RECYCLING Worn-out proteins are taken up by cells through phagocytosis/endocytosis and form an endosome Endosomes fuse with lysosomes, resulting in proteins that are released back into the Golgi apparatus for modification and recycling Summary of Functions within the Golgi Apparatus (Mescher, 2018) 2 of 3 CELL BIOLOGY: Note #14. Golgi Apparatus Structure & Function  IV) REFERENCES III) REVIEW QUESTIONS Cooper GM. The Cell: A Molecular Approach. 2nd edition. Sunderland 1) Which of the following statements is FALSE? (MA): Sinauer Associates; 2000. The Golgi Apparatus. Available from: a) Ribosomes facilitate the translation of mRNA into https://www.ncbi.nlm.nih.gov/books/NBK9838/ proteins Kumar, V., Abbas, A. K., & Aster, J. C. (2014). Robbins and Cotran b) The process wherein worn-out proteins are Pathologic Basis of Disease. W B Saunders Company. invaginated into the cell is called exocytosis c) The trans-Golgi is the concave side Mescher, A. (2018). Junqueira’s Basic Histology: Text and Atlas, Fiifteenth Edition. McGraw-Hill Education / Medical. d) Protein synthesis occurs in the rough endoplasmic reticulum 2) Which protein directs the movement of vesicles from the RER towards the cis Golgi? a) Clathrin b) Asparagine c) COP-I d) COP-II 3) In O-linked glycosylation, a sugar residue is added to the oxygen atom of which amino acids? a) Serine and Threonine b) Asparagine and Serine c) Asparagine and Threonine d) Serine and Lysine 4) Which molecule marks/tags proteins destined for lysosomal degradation? a) Ribonuclease b) Alkaline phosphatase c) Mannose-6-phosphate d) Hydrolase 5) The Golgi apparatus is especially prominent in which of the following types of cells? a) Goblet cells of bronchial epithelium b) Plasma cells c) Paneth cells of the intestinal epithelium Golgi Apparatus Structure & Function CELL BIOLOGY: Note #14. 3 of 3