Cell Structure And Protein Secretion

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Introduction to Biological Science - BIOL1361RecitationCell Structure and Protein SecretionA.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/181

Introduction to Biological Science - BIOL1361RecitationI. Tracing the Intracellular Pathway of Protein SecretionA. Label the nucleus, nuclear envelope, endoplasmic reticulum, Golgi apparatus, secretory vesicles,and extracellular space on the cell diagram on page 1.Use colored beads and the large diagram of a cell to reproduce a key experiment performed by JamesJamieson and George Palade in the 1960s. Palade was awarded the Nobel Prize in Physiology or Medicinein 1974 for his work on the roles of ribosomes, endoplasmic reticulum, and the Golgi apparatus in proteinsecretion. http://www.nobelprize.org/nobel prizes/medicine/laureates/1974/B. Move beads through cellular compartments according to instruction below and fill in the datatable. Times indicate when Jamieson & Palade took pictures to see where the radioactive leucine wasduring the actual experiment. You don’t need to wait between steps.1. Time 0: Put 10 beads in the extracellular space. The beads represent radioactively labeled leucine, anamino acid used to build proteins.2. 3-minute incubation: Move 9 beads into the endoplasmic reticulum and 1 into the nucleus.3. 7 minutes later: Distribute beads as follows: Nucleus – 1 bead; ER – 4 beads; Golgi apparatus – 4beads; secretory vesicles – 1 bead.4. 37 minutes later: Distribute beads as follows: Nucleus – 0; ER – 2 beads; Golgi apparatus – 7 beads;secretory vesicles – 1 bead.5. 117 minutes later: Distribute beads as follows: Nucleus – 0; ER – 2 beads; Golgi apparatus – 1 bead;secretory vesicle – 6 beads; extracellular space – 1 bead.Time(min)0Number of Beads in Cellular CompartmentNucleusRough sExtracellularspace----103737117C. Looking at the data, describe the pathway of synthesis and secretion of a protein such as theproenzyme trypsinogen.D. By what transport process does the secreted protein enter the extracellular space?A.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/182

Introduction to Biological Science - BIOL1361RecitationII. Organelles with their own circular DNAMitochondria in cross-section.1. Start at the dot on each mitochondrion and trace the line clockwise until you return to the dot. What doyou notice about this line? What structure does this line represent? What can you conclude about thisstructure based on the way it is drawn?2. Label the mitochondria above using the following terms: outer membrane, inner membrane, intermembrane space, matrix3. What are the cristae?4. What is in the intermembrane space?5. Describe the structural difference between the inner membrane and the intermembrane space.A.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/183

Introduction to Biological Science - BIOL1361RecitationThe Chloroplast1. Label the chloroplast below using the following terms: outer membrane, inner membrane,thylakoid, stroma, granum.2. What is the difference between a thylakoid and a granum?3. What is the stroma?4. Does a plant have both mitochondria and chloroplasts?A.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/184

Introduction to Biological Science - BIOL1361Cell StructureCell wallPlant/Animal/BothRecitationFunctionPlasma membraneNucleusNucelolusRibosomesSmooth endoplasmicreticulum (ER)Rough endoplasmic reticulum(ER)Golgi sIntermediate filamentsMicrofilamentsMicrovilliA.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/185

Introduction to Biological Science - Central vacuoleA.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/186

Introduction to Biological Science - BIOL1361RecitationTeaching Tips for Peer LeadersThis week emphasize the relationship between cell structure and function. Students usually can label theparts of the cell. Explaining the functions of each organelle, especially the process of protein secretion ismore difficult.Part I.A) Have students work in pairs or threes. Each group needs an 8 x 10 cell diagram (page 1) and 10 coloredbeads. Make sure students label the nucleus, endoplasmic reticulum, Golgi apparatus, and secretoryvesicles. The shaded areas represent the space between the nuclear membranes and the cisternae (orlumen) of the ER, Golgi apparatus, and vesicles. The colored beads represent radioactively labeledleucine, an amino acid. Jamieson & Palade incubated slices of guinea pig pancreas in 14C leucine for 3minutes. At the end of 3 minutes, the 14C leucine solution was removed and replaced with nonradioactive solution. During that time, pancreatic acinar cells (the cells that produce trypsinogen,chymotrypsinogen and all the other pancreatic digestive enzymes) transported the leucine across thecell membrane and into the cytoplasm. At the end of the 3 minute incubation, the tissue slice was fixedand prepared for autoradiography, a technique where film is placed on top of the tissue sections,allowing the radioactivity to expose the film. The film is developed to see where the radioactivity iswithin the cell or tissue. Jamieson & Palade found 90% of radioactivity in the endoplasmic reticulumand 10% in the nucleus. Students mimic this in step 2 by moving 9 beads into the endoplasmicreticulum and 1 bead into the nucleus.Jamieson & Palade fixed and analyzed additional tissue slices 7 minutes, 37 minutes, and 117 minutesafter the 3-min incubation with radioactive leucine ended. At each time point, they photographed thelocation of the 14C leucine. Students move the beads to different organelles to represent what theresearchers saw.B) Students need to move the beads around in the cell and fill in the table with data on where the beadswere at each time.C) Emphasize that the colored beads represent radioactive leucine, a tracking device for protein locationwithin the cell. Wherever the tracking devices are, that’s where the proteins containing them are. Thepoint of this experiment is to help students understand the sequential roles played by rough ER, Golgiapparatus, secretory vesicles and exocytosis in protein synthesis and secretion. After pairs or groupshave completed A – D, send someone to the board to explain the process of protein secretion. Ask theaudience to correct any mistakes as you notice them. You can start with a volunteer who is willing todraw the nucleus, ER, Golgi, and vesicles.D) The protein is secreted by exocytosis (review course textbook if necessary).Part II. Emphasize to students that they must understand the structure of mitochondria and chloroplaststo understand cellular respiration and photosynthesis.Point out that the line drawings of mitochondria are cross-sections. Mitochondria look different in crosssection, depending on how they are sliced – transverse (the round section) or longitudinally (the ovalsection). Use a sliced cucumber as an analogy: The cut surface is an oval if you cut it lengthways, but thecut surface is a circle if you cut across it.A.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/187

Introduction to Biological Science - BIOL1361RecitationPracticing Vocabulary. This vocabulary exercise is intended for individual study outside of recitation.You can recommend they turn this exercise into matching cards and see if they can match terms anddefinitions without looking at their notes or the book.Point out that nucleus & nucleolus and chromatin & chromosome can be confusing terms. Help themcome up with a way to remember the difference.Notes to FacultySupplies needed in addition to the hand-out: Enough plastic beads to give 10 beads to each pair or group ofstudents.A.O. Cheek & D. Pattison, Department of Biology & Biochemistry, University of HoustonAttribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)Rev. 1/3/188

I. Tracing the Intracellular Pathway of Protein Secretion A. Label the nucleus, nuclear envelope, endoplasmic reticulum, Golgi apparatus, secretory vesicles, and extracellular space on the cell diagram on page 1. Use colored beads and the large diagram of a cell to reproduce a key experiment

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