Biochemistry for NutritioWDietetics Students: Lorraine Handler Sirota Brooklyn College, Brooklyn, NY 11210 Competence in biochemistry is required of all students seeking to qualify in three of the four areas of dietetics specialization under Plan N of the American Dietetic Association (ADA), the accrediting organization for dit,titians. Although eenwal euidelines have been publishrd, desired comprtmce in specikc subject matter and levels of knowledge have not been established (1). An understanding of the basic concepts of nutrition is deen dent, to a larae demer, w o n familiarity with hiuchem~stry. ~ u t r i t i o nthe , sciencethat &terprets the relationship of food to the molecular and physiologic processes controlling the functions of all living organisms' has evolved from work done over the past 200 years by chemists and physiologists. Despite the essentialness of biochemistry to the nutrition curriculum, there is no literature concerning desirable competencies or course content in hiochemistry for dietitians. T o determine the course content and priorities in the teaching of hiochemisrry to nutritionldietetics students, two different questionnaires were prepared and mailed to the "I)irectort~fDiewtirs" at a11 251 institutirms that offered dietetics programs under Plan IV of the ADA in 1979-1980. They were requested to complete the questionnaire for departmental information and to forward the biochemistry ouestionnaire to the individual responsible for teaching the biochemistry course most frequently used to satisfy the reouirrments of the ADA. The names and mailing addreiies of the directors were obtained from the 1980 Directory of Dietetic Programs (2). Completed responses were returned by 186 (74%) of the dietetics directors and 153 (61%) of the biochemistry instructors. Respondents were highly representative of all programs offered in the United States in terms of geographic location, size of the dietetics program, size of the college, and
430
Journal of Chemical Education
affiliation of the college. The survey was also very comprehensive in terms of the total number of students enrolled in dietetics programs. The responding biochemistry questionnaires represented institutions with 2,400 out of the 3,000 undergraduate dietetics students estimated by the ADA to be eraduated in June 1980. he hiochemisrry qnrstionnaire was drveloprd using as a ruide the tov~cssuarested hv the Amrr~tnn('hrmical Suciety y3). Then items (subtopicsj were derived from this investigator's own experience and from textbooks designed for introductory level courses. For each topic, 4 to 5 subtopics were presented, with each subtopic reflecting a different level of knowledge of the topic arranged so that items went from s i m ~ l to e more difficult. The items were usually ordered from thc ;enerally descriptive u, those that were more technical and mathematical. There were :I0 general topics. and a wtal of 1-19 subtopics, hereafter referredto as "items." The biochemistry instructor was requested to rate each item according to the amount of emphasis placed on it in hisher course as currently given. The criteria for rating were provided for the instructor as follows: A represented "essential" and meant that lecture andlor textbook assignments were always devoted to this topic and exam questions on the item were always given; B represented "desirable" and meant that there was less emphasis than for "essential," usually with some lecture time andlor textbook assignments devoted to the topic, and some exam questions were usually given; C represented "not important" and meant that some mention was given in
'
These functions include the utilization of nutrients, production of energy, elimination of wastes, the manufacture of all substances required for growth, maintenance, and reproduction.
lecture andlor textbook assignments, but was covered only when time permitted; and D represented "irrelevant" and meant that the subject matter was omitted, or hardly ever covered. An A rating by a respondent gave that item a scorr of 1; B, 2; C , 3; D, .I. l'he mean score for each item was computed by summing the scores for all questionnaireson which the topic had heen rated. and then dividinr bv the total number of responses for that topic. The meanscores were then arranged in order, with the lowest mean scores representing the item(s) more highly rated, and the highest mean scores indicating the item(s) having least priority. The items were also assigned to categories which represernt levels and types of information or knowledge. The frequency with which items were assigned to a category and the list of items arranged in order of decreasing priority, by rank order of mean scores and category to which assigned, may be obtained upon request. In general, a high priority was placed on descriptive or qualitative information such as definitions, simple structures, overall reactions of common substances. and reactions explained in general terms. Topics ranked of lesser importance include those emvhasizine mechanistic and auantitative calculations biochemistry such respir&ry quotient (R.Q.); of enerrv from fat and carbohvdrate: enzyme kinetics: suecific structures of vitamins, ketones, steroids, and metabolic intermediates; enzymatic and hormonal controls of pathways; and all items relating to the hexosemonophosphate shunt and photosynthesis. For example, the student's ability to define an enzyme ranked as # 1,whereas naming the enzymes which control the rate-limiting reactions of intermediary metabolism ranked as #97.5; understanding the mechanisms by which specific enzymes involved in digestion and cell metabolism are controlled ranked as #97.5; and calculating the velocity of a reaction usine" the Michaelis-Menten eauation ranked as # 124.5 There was a tendencv to rate all items hieh-as "essential" or "desirable." Most oithe 149 items listei were included in existine courses and relativelv few were omitted or ziven minimal coverage. There was a noticeable consistency to the ratines of similar tovics, even though thev were located in different parts of the questionnaireResponses to general information questions such as lectures (hrlwk), lab (hrlwk), type of academic calendar, size of classes, types of students' majors, and textbook used were also compiled. The chi-square test, Pearson correlation coefficient, and the one-way analysis of variance were used where appropriate. Analysis for students' majors in the biochemistry classes revealed that 14 out of 150 (9%) were designed for nutrition1 dietetics majors only; 67 (45%)were open to all nonchemistry majors including dietetics majors, but not to chemistry majors, and 69 (46%)were open to both chemistry and nonchemistry majors. Large institutions offered more of the biochemistry courses specific for all nonchemistry majors apart from chemistrv.maiors. The common body of information that is taught to all students would enable them to describe in eeneral terms. the structure of the energy nutrients-fats, earbohydrates.and proteins-and the reactions of intermediary metabolism by which the building blocks are metabolized under enzymatic control for the purpose of providing energy; namely, through glycolysis, the Krebs cycle, and the electron transport system. Although there was a common body of information that was taught to all classes, there were certain items that were more highly emphasized in each of the three types of classes, depending upon the students' majors. For example, if a class consisted of dietetics majors only they were more likely to be expected to know the enzymes, coenzymes, and hormonal
.
controls involved in fatty acid synthesis and oxidation; how to define an allosteric enzvme; the metabolic urocesses related to the excessive formation of ketone bodies; and the abnormalities in metabolic uathwavs which are associated with metabolic abnormalities or thk disease state-for example, diabetes, starvation. obesitv. If dietetics majors were in classes with all the other nonchemistry majors, in addition to a common core of information they were more likely to be expected to know the following specifics: the ketone bodies, the broad category of steroids, the relationship between structure and general function of proteins, and the fundamental comuouents of nucleic acids and their bonding properties. If dietetics maiors were in classes which contained both chemistry and nonchemistry majors, they were more likely to he expected to know in addition to a common core of information, the following specifics: the reartimu of the photosynthetic process; iusrrumentation and techniques of protein identification; how tocalculate isoelectri~.points, also the pH of buffers using thr Henderson-Hasielhalch equation, velocity of reactiuns using the Michaelis-Menten equation. freeenergy change in relation to the equilibrium constant; and how to draw the specific structures ot all thr naturally occurring a-aminoacids. purines, and pyrimidines; intermediates of the hexosemonor~hosuhateshunt: and s~hinculirids. To some degree, th' bioEhemistry instructbrs' &iffiring choices of subject matter may he based upon what the instructors' considered to be relevant to the students' major fields. Thus, the dietetics-oriented hiochemistrv instructor. the one who had classesspecifically for dieteticsstudents, 01 even for all nonchemistry maiors including dietetics students, apparently emphasizedcertain of the clinically relevant material, whereas the chemistry-oriented instructor emphasized quantitative and theoretical aspects of biochemistry.2 Differences in course content may be influenced by factors not readily measurable. The format of the questionnaire permitted us to examine responses of instructors with regard to the extent t o which items were covered in their resnective courses and the levels at which these were taught. It did not reveal the more subtle distinctions that relate to the instructor's philosophy about student preparednks, actual level of ex~ectationon examinations. eradine vrocedures. and what the instructor believes the dieittics &d allied health majors should know as a result ufstudving biuchrmistrv, all oi which may be factors in the ~tude&~resultantknowledge and comvetencv. 1t-is also possible that the instructor's choice of subject matter may actually reflect what is perceived as the student's intellectual abilities. Both students and teachers often consider the quantitative and abstract aspects of biochemistry-e.g., calculations involving ratios or concepts involving enerm--difficult. Given the finding that on the average more majors in mathematics, physics, and chemistry use ;bstract or formal reasoning consistently than majors in biology and nutrition ( 4 , 5 ) ,it is likely that chemistry instructors of majors and nonmajors have, by trial and error, come to present their material in a more or less abstract or formal way depending on their audience. Some teachers of eeneral. oreanic. and biochemistrv have tried to answer wharthey perceive as the needs of nutrition and other allied health students by offering special courses and special textbooks ( 6 9 ) . Analysis for frequency of textbook choice and association of textbook choice with other variables demonstrated that a total of 38 different textbooks were used alone or in combination with each other for biochemistry lecture classes. Of the 147 responses, 137 indicated use of a single textbook; 10 used two or more books in varying A list of the items significantly differentfor each of the groupings is available upon request.
Volume 61 Number 5 May 1984
43 1
combinations. Each textbook mentioned was evaluated for subject matter and level of the text and was assigned to one of the followine cateaories-I. 11.111. IV, V, VI, VII, or VIII according to the following c l a & f i c a ~ o n ~ :
Table 1. Frequency (I of )Total Number of Books In E a c h Category and percentage Distribution of Textbooks Assigned i n Biochemistry Courses Taught i n Dietetics Programs. Grouped ~ c c o r d i tno~Level and Focus of Book ( N = 149)
I = short version for allied health, or introductory level for
nonmaiors
I. Short Version far Allied Health; Introductory Level far Non-Majors ( f =
70.5)
V = combination of organic and biochemistry VI = review and independent-studybooks VII = supplementary texts VIII = all others, miscellaneous Although categories IV and V are sub-categories of I, they are treated separately, since the level at which they deal with the biochemistry is more elementary than that of books in category I. Table 1lists the textbooks used according to the category to which the textbook was assigned, and the percentage distribution and frequency with which each textbook was used. Of the 10 classes which used two or more books, 6 used their major text from category I, 1from II,2 from 111, and 1from IV. The supplementary books covered related subject matter such as cell biology, bioenergetics, and nutrition. For required laboratory courses, 57% of the respondents renorted that thev used a manual desiened hv the staff or fkulty, or handouts; and 13% used 1of the i 0 published manuals listed according to percentage frequencies in Table ."' The chi-square test of the possible relationship between the type of textbook used and the composition of the class according to students' majors revealed a difference between the classes in choice of textbook ( ~ =2 52.9, d.f. = 10, p =
