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Multiple Choice Tests—Are Four Options as Good as Five?
200
Monitor CHARLES F A BRYCE Department o f Biological Sciences Napier College o f Technology Edinburgh, Scotland
Barton, J S Protein Denaturation and Tertiary Structure. J Chemical Education 63, 367-368 (1986) Viscosity measurements on solutions of bovine serum albumin are used as indices of protein denaturation and alteration in tertiary structure. Samples of native bovine serum albumin can be used and compared with both acid-denatured serum albumin, and reduced and acid-denatured serum a l b u m i n . Ostwald viscomcters with flow times of 80-100 s for water are used in a thermostatted water bath at 250C. A brief review of the theory of capillary viscometry is provided in the introduction with the recommendation that reduced viscosity (specific viscosity (Nsp)/ concentration) be used to assess conformational changes in the protein. The estimated time allowance for students undertaking this practical is two to three laboratory periods of 3 hours duration which includes time to become familiar with viscometer use. In the experiment the albumin is denatured by the addition of HCI to bring the pH to 2. 2-Mercaptoethanol is added subsequently to produce further conformational changes by cleavage of disulphide bonds. The results obtained for the three conformational states of the protein showed statistically significant differences whereas reduced viscosities for any one state, at a variety of different protein concentrations (10-40 mg/ml) showed no statistically significant differences. Denaturation of albumin could also have been accomplished by the use of 8 M urea or 6 M guanidine hydrochloride. [Department of Biochemistry, Washburn University, Topeka, KS 66621, USA]
Desloges, C Informatics and Robotics in Biochemistry. Ann Biochim Clin Qu~ 24, 85, (1985) This short abstract in French, outlines the types of benefits that can be gleaned from the use of modern microcomputers in a biochemistry laboratory. These include such applications as constant monitoring and control of a wide variety of biochemical reactions, data acquisition, baseqine correction, data manipulation, quality control, data storage and data transmission to other users. In some instances the examples cited are very much more specific than the above generalisations. [Department of Biochemistry, Coulter Electronique du Canada Lt~e, Anjou, Qu6bec,, H1J 2H9, Canada]
Falconer, A C and Hayes, L J The Extraction and Partial Purification of Bacterial DNA as a Practical Exercise for GCE Advanced Level Students. J Biological Education 20, 25-26 (1986) The authors describe a simple method for the extraction and purification of bacterial D N A which can be completed in two 90minute sessions. E coli cells are first treated with SDS to lyse the cell membrane and the resultant suspension is then incubated with trypsin/chymotrypsin to hydrolyse associated proteins. The protein-free D N A is then isolated using two phenol extractions, one phenol/trichloromethane extraction, one trichloromethane/ pentan-2-ol extraction and finally an ethanol precipitation. An alternative to perchloric acid hydrolysis is suggested in which the isolated D N A is treated with hydrochloric acid at 100°C for 30 minutes to yield the constituent bases which can then be separated using ascending chromatography and compared with standard samples of the four bases. The authors outline some of the possible experiments that can be undertaken to study the
BIOCHEMICAL EDUCATION 14(4) 1986
physicochemical properties of the isolated DNA. A list of reagents and preparation details are supplied in an appendix. [Biology Department, Richard Taunton College, Highfie!d, Southampton, SO9 5GF, UK]
Hodson, D Multiple Choice Tests - - A r e Four Options as Good as Five? Education in Chemistry 23, 84-86 (1986) The number of choices in multiple-choice test items is intrinsically associated with such considerations as overall performance, discrimination index and test reliability. Five would seem to be the optimal choice for the number of test item choices by a number of formal examining boards and this view is supported by standard texts on assessment techniques. However, this conclusion in relation to multiple-choice test construction derives largely from professional judgement and personal hunch rather than as the result of empirical evidence, particularly in science. The author designed an experiment in which 'O'- and 'A'-level students in chemistry were offered one of two tests, one with five options per question, the other with four. In the case of the latter, the test items were identical and appeared in identical order, the only difference being that one of the distractors was eliminated (the least used, determined by a pre-test using another cohort of students at the same academic level). From the results it would appear that overall scores, average discrimination values, standard deviations and test reliability had only very slight and statistically insignificant differences between the two forms of the test. The author then goes on to make a case for varying, in any one test, the number of distractors as dictated by the test item rather than having a standard format for all questions. [Department of Chemical Education, University of Manchester, Oxford Road, Manchester, MI3 9PL, UK]
Maier, M L Teaching Biochemistry: A Topical Approach. J Chemical Education, 63, 239-241 (1986) The article gives experimental details of three laboratory practicals designed to illustrate enzyme specificity. The author's aim is to package these in the guise of showing a need for a balanced diet. In the first experiment tyrosinase is extracted from potatoes and its activity assayed directly, or in the presence of catechol, hydroquinone or resorcinol. Enzyme activity is measured simply by observing colour changes after a period of 5 and 10 min. In the second experiment solutions of D-glucose and L-glucose are incubated with a yeast suspension and the nature of the products of the reaction, if any, are tested. For example the production of CO2 can be tested by its reaction with limewater, alcohol can be tested by smell and/or distillation and subsequent analysis. The third experiment tests the specificity of c~-amylase from saliva by using starch and cellulose as substrates. Hydrolysis is tested by use of the iodine test or by Benedict's reaction. [Department of Biology, St Joseph's College, Brooklyn, New York 11205, USA] Russo, S F and Moothart, L Kinetic Study of the Enzyme Lactase J Chemical Education 63, 242-243 (1986) The authors comment briefly on the biological role of lactase in the hydrolysis of lactose and of lactose intolerance leading to microbial degradation in the colon to produce organic acids and CO2 resulting in fermentative diarrhoea. The article then describes an enzyme kinetic study using a synthetic substrate, Onitrophenyl-i3-D-galactopyranoside which, on hydrolysis, yields a coloured product, the rate of production of which can then be monitored at 420 nm. Full details are provided of the preparation of buffer solutions and stock solutions. [Department of Biochemistry, Western Washington University, Bellingham, W A 98225, USA]
Monitor CHARLES F A BRYCE Department o f Biological Sciences Napier College o f Technology Edinburgh, Scotland
Barton, J S Protein Denaturation and Tertiary Structure. J Chemical Education 63, 367-368 (1986) Viscosity measurements on solutions of bovine serum albumin are used as indices of protein denaturation and alteration in tertiary structure. Samples of native bovine serum albumin can be used and compared with both acid-denatured serum albumin, and reduced and acid-denatured serum a l b u m i n . Ostwald viscomcters with flow times of 80-100 s for water are used in a thermostatted water bath at 250C. A brief review of the theory of capillary viscometry is provided in the introduction with the recommendation that reduced viscosity (specific viscosity (Nsp)/ concentration) be used to assess conformational changes in the protein. The estimated time allowance for students undertaking this practical is two to three laboratory periods of 3 hours duration which includes time to become familiar with viscometer use. In the experiment the albumin is denatured by the addition of HCI to bring the pH to 2. 2-Mercaptoethanol is added subsequently to produce further conformational changes by cleavage of disulphide bonds. The results obtained for the three conformational states of the protein showed statistically significant differences whereas reduced viscosities for any one state, at a variety of different protein concentrations (10-40 mg/ml) showed no statistically significant differences. Denaturation of albumin could also have been accomplished by the use of 8 M urea or 6 M guanidine hydrochloride. [Department of Biochemistry, Washburn University, Topeka, KS 66621, USA]
Desloges, C Informatics and Robotics in Biochemistry. Ann Biochim Clin Qu~ 24, 85, (1985) This short abstract in French, outlines the types of benefits that can be gleaned from the use of modern microcomputers in a biochemistry laboratory. These include such applications as constant monitoring and control of a wide variety of biochemical reactions, data acquisition, baseqine correction, data manipulation, quality control, data storage and data transmission to other users. In some instances the examples cited are very much more specific than the above generalisations. [Department of Biochemistry, Coulter Electronique du Canada Lt~e, Anjou, Qu6bec,, H1J 2H9, Canada]
Falconer, A C and Hayes, L J The Extraction and Partial Purification of Bacterial DNA as a Practical Exercise for GCE Advanced Level Students. J Biological Education 20, 25-26 (1986) The authors describe a simple method for the extraction and purification of bacterial D N A which can be completed in two 90minute sessions. E coli cells are first treated with SDS to lyse the cell membrane and the resultant suspension is then incubated with trypsin/chymotrypsin to hydrolyse associated proteins. The protein-free D N A is then isolated using two phenol extractions, one phenol/trichloromethane extraction, one trichloromethane/ pentan-2-ol extraction and finally an ethanol precipitation. An alternative to perchloric acid hydrolysis is suggested in which the isolated D N A is treated with hydrochloric acid at 100°C for 30 minutes to yield the constituent bases which can then be separated using ascending chromatography and compared with standard samples of the four bases. The authors outline some of the possible experiments that can be undertaken to study the
BIOCHEMICAL EDUCATION 14(4) 1986
physicochemical properties of the isolated DNA. A list of reagents and preparation details are supplied in an appendix. [Biology Department, Richard Taunton College, Highfie!d, Southampton, SO9 5GF, UK]
Hodson, D Multiple Choice Tests - - A r e Four Options as Good as Five? Education in Chemistry 23, 84-86 (1986) The number of choices in multiple-choice test items is intrinsically associated with such considerations as overall performance, discrimination index and test reliability. Five would seem to be the optimal choice for the number of test item choices by a number of formal examining boards and this view is supported by standard texts on assessment techniques. However, this conclusion in relation to multiple-choice test construction derives largely from professional judgement and personal hunch rather than as the result of empirical evidence, particularly in science. The author designed an experiment in which 'O'- and 'A'-level students in chemistry were offered one of two tests, one with five options per question, the other with four. In the case of the latter, the test items were identical and appeared in identical order, the only difference being that one of the distractors was eliminated (the least used, determined by a pre-test using another cohort of students at the same academic level). From the results it would appear that overall scores, average discrimination values, standard deviations and test reliability had only very slight and statistically insignificant differences between the two forms of the test. The author then goes on to make a case for varying, in any one test, the number of distractors as dictated by the test item rather than having a standard format for all questions. [Department of Chemical Education, University of Manchester, Oxford Road, Manchester, MI3 9PL, UK]
Maier, M L Teaching Biochemistry: A Topical Approach. J Chemical Education, 63, 239-241 (1986) The article gives experimental details of three laboratory practicals designed to illustrate enzyme specificity. The author's aim is to package these in the guise of showing a need for a balanced diet. In the first experiment tyrosinase is extracted from potatoes and its activity assayed directly, or in the presence of catechol, hydroquinone or resorcinol. Enzyme activity is measured simply by observing colour changes after a period of 5 and 10 min. In the second experiment solutions of D-glucose and L-glucose are incubated with a yeast suspension and the nature of the products of the reaction, if any, are tested. For example the production of CO2 can be tested by its reaction with limewater, alcohol can be tested by smell and/or distillation and subsequent analysis. The third experiment tests the specificity of c~-amylase from saliva by using starch and cellulose as substrates. Hydrolysis is tested by use of the iodine test or by Benedict's reaction. [Department of Biology, St Joseph's College, Brooklyn, New York 11205, USA] Russo, S F and Moothart, L Kinetic Study of the Enzyme Lactase J Chemical Education 63, 242-243 (1986) The authors comment briefly on the biological role of lactase in the hydrolysis of lactose and of lactose intolerance leading to microbial degradation in the colon to produce organic acids and CO2 resulting in fermentative diarrhoea. The article then describes an enzyme kinetic study using a synthetic substrate, Onitrophenyl-i3-D-galactopyranoside which, on hydrolysis, yields a coloured product, the rate of production of which can then be monitored at 420 nm. Full details are provided of the preparation of buffer solutions and stock solutions. [Department of Biochemistry, Western Washington University, Bellingham, W A 98225, USA]