BSCI330 Ades Final Exam Lecture Notes Lecture 31 Globlet Cell Involved in the secretion of mucins proteins Found in the intestines Mucins are responsible for the making of gel like substances mucus These are secreted in the intestines o To help protect the intestinal cells from the damage that digestive enzymes could induce on the absorbing cells o Protects the walls of the intestines by lubricating the movement of substances as they travel across the digestive tract Mucins are heavily glycosylated with glycoproteins o These are responsible for the retention of water o Sugars and sugar chains on the proteins are responsible for the entrance of substances into the globlet cell Cell is polarized For those polarized cells one end of the cell is different in its composition while the other end has a different composition Top part faces the lumen and vesicles contain the mucin fuse with the membrane dump these contents In addition to the differential distribution of proteins along the plasma membrane of the cells the orientation of some organelles such as the Golgi apparatus are structured in such a way o Active in the packaging of proteins destined for secretion Rough ER o Has a specific orientation Globlet Cell Cellular matrix The mitochondria have an asymmetrical distribution o Proteins in the mitochondria are different from those found in the other organelles BSCI330 Ades Newly made Proteins Have sequences on them that are responsible for the final locations of proteins Sorting newly produced proteins Co Translational Pancreatic model Assembly of secretory vesicles Signal sequences Core glycosylation Sorting lysosomal enzymes Integral membrane proteins Pancreatic Acinar Cell Specialists that produce digestive enzymes package these enzymes in vesicles wait for food to be ingested hormone interacts with the cells binds to receptors and target membranes of those cells elicit an internal signal and induce fusion for secretory vesicles with the plasma membrane o A cross section of those pancreatic cells o Pancreatic duct o These cells produce digestive enzymes which are secreted by the pancreas into the intestines to help digest ingested food Example of Regulated Secretion BSCI330 Ades o As food leaves the stomach and moves into the upper part of the small intestine a hormone is released by duodenum cells sending a signal where enzymes must be dumped into the intestines to digest the ingested material so that it would absorbed o Cholecytoinin Peptide Hormone Protein secreted by duodenum cells Finds its way to the pancreatic acinar cells binds with it triggers the fusion of secretory vesicles with the plasma membrane When calcium levels rise the v SNARES and t SNARES twist Two membranes will be able to merge Proteins that are packaged in the vesicles will be able to fuse with the plasma membrane Eukaryotic Cells Protein synthesis in eukaryotes o Free ribosomes o ER Bound ribosomes o Mitochondria and chloroplasts Activity at the sites for protein synthesis o Ribosomal Sub unit acids Small ribosomal sub unit will bind to the mRNA which has the 5 end 3 end poly A tail At the right codon the large ribosomal sub unit will add amino The ribosome moves from the 5 3 Amino acids are delivered within the tunnel of the large ribosomal amino acids Ribosome moves around with one step initiating another site where another amino acid and etc BSCI330 Ades The large ribosome is along the mRNA the longer the segment of amino acid Amino end is the one that is synthesized first Carboxylic end is coded for the codons Ribosomes make about 13 unique proteins in the mitochondria Most of the proteins in mitochondria are made outside The last group of ribosomes can be found in the endoplasmic the reticulum Know the structure of the poly ribo some BSCI330 Ades mRNA translation surrounded by several ribosomes The Rough ER Appears as flattened vesicles Studded with Ribosomes o The large ribosomal sub unit is the one sitting closest to the plasma membrane o The small ribosomal sub unit is the one sticking into the cytoplasm o It has been suggested long before the questions was solved that these cells are enriched in the rough ER membrane as compared to non secreting cells o The inside of the ER is part of the lining of the lumen The Smooth ER The membranes of the smooth ER are more like tubes The organelle has different functions compared to Rough ER o Contain enzymes for lipids or steroids o Contain detoxification enzymes Used for lipid hormones In tissues active in detoxification liver kidney etc contain detoxification enzymes found in the smooth ER BSCI330 Ades Barbituates Used to treat patients with epilepsy but experiment involved mouse organisms Sleep more concentrated Sleep less drug is diluted The enzymes involved in the degradation of barbituates found in the liver o These enzyme levels rise smooth ER is more active o The mass of the smooth ER would be enormous in animals that have been exposed to the drug hypertrophy Smooth ER has two functions o House enzymes Cytochrome p450 o Calcium storage in muscle cells Pulse Chase Studies Pancreatic Acinar Cells George Palade 1912 Nobel Prize in Medicine and Physiology 1974 o 1 Take an Erlenmeyer flask and add slices of pig pancreas Instead of the dye Add radioactive 3H Leucine That leucine will get into tissue slices it will be incorporated into proteins and any protein that has been made right up to the addition of the leucine eventually will be produced as radioactive Radioactivity would occur in the cytoplasm o 2 Incubate the slices with radioactive amino acid o 3 Follow the production of the radioactive protein Traced the path of newly made proteins in the cell BSCI330 Ades The Results of these Pulse Studies The path of synthesis of proteins destined for secretion begins on the rough ER These proteins are transferred to the Golgi Apparatus Transferred to vesicles between the Golgi and secretory vesicles Eventually delivered to the zymogen vesicles zymogen vesicles destined for secretion Autoradiography Coat the cells with photographic emulsions colloid silver bromide o The decay of the proton will express a silver granule o The oxidation of these silver granules can be detected by taking the photographic emulsion and using a photograph to capture that image Acinar Cell viewed under a light micrograph and electro micrograph a Secretory granules nucleus rough ER o Dark speckled radioactive leucine b Golgi showed activity c Between Golgi and secretory granules d
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