Final Exam Fall 2010 KEY

Final Exam Fall 2010 KEY - Biol 221 Fall 2010 NAME_KEY_...

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Biol 221 Fall 2010 NAME______________ KEY _______________________ Final Exam [TEAR OFF THE FIRST TWO PAGES OF THE EXAM, STAPLE THEM TOGETHER AND HAND THEM IN ALONG WITH THE SCANTRON.] Short Answer. 40 points (5 points each). 1. List the four major biological macromolecules, the monomers of which they are composed and the bonds that put these monomers together. Name a structure in a bacterium that is made from each macromolecule. MACROMOLECULE MONOMER(S) BOND STRUCTURE Carbohydrates monosaccharides glycosidic LPS core and O-antigens, (sugars) peptidoglycan, glycocalyx Proteins amino acids peptide Many – enzymes, transport proteins, cytoskeleton, etc. Nucleic Acids nucleotides phosphodiester DNA, RNA Lipids glycerol + ester (glyceride) cell membrane fatty acids (accept h’phobic intx) approx. 1.25 points for each line correct 2. Synechococcus lividus detects an environmental inducer , but the inducer is never actually present inside the cell . The gene bchA is transcriptionally regulated in response to the inducer, and is under negative control . Sketch a diagram showing S. lividus and its bchA gene in the presence and the absence of the inducer. State whether the bchA gene is expressed or not expressed under each condition. Label the important parts of the regulatory system. Explain how the inducer regulates bchA without being present in the cell. absence of inducer presence of inducer diagram: (+3) Is bchA expressed? NO YES (+1) Explanation: Inducer triggers autophosphorylation of sensor kinase, which transfers phosphate to response regulator (repressor), inactivating the repressor so that it fails to bind to the operator. Unblocking the operator turns the gene on. (+1) bchA bchA Sensor Kinase Response regulator (is repressor) operator ~P
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3. List the steps involved in activation of a B cell. Explain how your body prevents activating B cells that recognize self antigens. B-cell receptor binds foreign antigen and internalizes B-cell digests foreign antigen and presents epitope on MHC-II effector T H cell binds to epitope on MHC-II and releases cytokines B-cell differentiates into plasma cells and B memory cells Self recognition is prevented by the clonal deletion process. If a B cell receptor recognizes an antigen (assumed to be self) while the B cell is still in bone marrow (before it has been released to the serum), the B cell becomes anergic. (+1 point each) 4. Explain the concepts of antigenic drift and shift in influenza virus. Be sure your answer includes the following: how different are antigens after drift/shift reason for antigenic drift/shift proteins usually affected by antigenic drift/shift frequency of antigenic drift/shift consequences of antigenic drift/shift Drift is a small change that occurs because the RNA influenza virus is not proofread . Generally hemagglutinin proteins change slightly, but frequently (yearly) . This results in a new flu outbreak every year , for which a new vaccine is required. Shift is a major change
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Final Exam Fall 2010 KEY - Biol 221 Fall 2010 NAME_KEY_...

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