Workbooklet2010 - BCH 210H Enzyme and Metabolism Workbook...

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BCH 210H Enzyme and Metabolism Workbook Dr. R.R. Baker Department of Biochemistry University of Toronto
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Enzymes Introduction/Classification 1. To what class of enzyme does carbonic anhydrase belong? Can you explain this? 2. Carbonic anhydrase certainly acts very rapidly. Can you think of one reason for its considerable speed? 3. Hydrolases often catalyze very favourable reactions. For example: Pyrophosphate + H 2 O 2 inorganic phosphate However, hydolases are not favourable in the reverse direction: 2 inorganic phosphate pyrophosphate + H 2 O Can you explain why this is so?
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Enzyme Specificity 1. In the body, alcohol dehydrogenase (ADH) converts ethanol into acetaldehyde. Then acetaldehyde undergoes a further enzyme catalyzed oxidation. What would be the products of ADH if CH 3 -OH was the substrate? What is CH 3 -OH? 2. Can you explain the toxicity that develops if someone ingests CH 3 -OH? Can you name a common domestic source of CH 3 -OH? 3. You are given 1 millimole (10 -3 moles) of the peptide: MLLWKIKGGRTFPKGG. This is completely hydrolyzed in solution at pH 8 by the enzyme trypsin (which is active in the small intestine). a) What are the products of this protease, when the peptide is completely degraded by trypsin? How many moles of water are needed for this reaction? b) Why do you think that trypsin has an alkaline pH optimum (pH 8)?
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Enzyme Active Site 1. If someone has a blocked tear duct, they often have eye infections. Why do you think this is so? 2. A small enzyme E is attacked by a protease P at 4 o C for a very brief time period. The incubation with P breaks only one peptide bond in E, and E does not fall apart in solution, but continues to be an active enzyme. a) Why do you think that the incubation of E with P is carried out at low temperature for a brief period of time? b) Can you explain why E still works after the one peptide link is severed? c) After the brief attack by P, E can be separated into its two components using gel filtration chromatography. However neither of these smaller fragments is enzymatically active. What could this observation suggest?
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Enzyme Regulation 1. The enzyme COX contributes to eicosanoid formation in small cells called platelets, that are found in the blood. Platelet eicosanoids can promote the formation of thrombi (cellular aggregates in blood) that can lead to vessel occlusion (blockage) in heart attack and stroke. If COX is an active enzyme in platelets, and oxygen is available in the blood, what regulates the production of eicosanoids? And thus regulates the possibility of thrombus formation by platelets? 2. If there were no protein phosphatase activity in muscle cells, what problem would you experience in the metabolism of glycogen (i.e. how glycogen is synthesized and broken down)? 3. For PFK-1 it was observed that ATP at physiological concentrations (2-4mM) in the
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This note was uploaded on 11/23/2010 for the course BCH BCH210 taught by Professor Deber during the Fall '08 term at University of Toronto- Toronto.

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Workbooklet2010 - BCH 210H Enzyme and Metabolism Workbook...

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