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(4) Put into practice their previous knowledge and other appropriate information in order to achieve full under- standing of the metabolic alterations in individuals suffer- ing from syndromes of malnutrition or intoxication. (5) Select either the techniques or the biological materials to carry out clinical, toxicological or nutritional studies. (6) Carry out nutritional, toxicological and clinical evalu- ations on experimental animal models. (7) Apply the main statistical methods used for quality control in laboratories where these subjects are studied. (8) Design simple experiments for the study of situations where there is lack of nutrients, or pathological alterations or changes produced in response to xenobiotics. (9) Be familiar with the appropriate computing tech- niques.

In the teaching of each subject, 36 hours are devoted to lectures, 76 hours to laboratory, 12 hours to seminars and 2 hours to classes. Some practical teaching is carried out in National Research Centers. The practical course has been designed in such a way that it links the three disciplines in their methodology and in the analysis of results. It is subdivided as follows: (a) Analysis of biological samples: determination of metabolites, enzymes and foreign compounds that are considered biological markers in the study of nutritional status, clinical symptoms or intoxication. (b) Experiments on digestion and absorption in vivo and in vitro. (c) Experimental models: - - Experimental scurvy - - Evaluation of the protein quality of foods. - - Atherosclerosis and diabetes mellitus - - Acute toxicity - - Drug interactions.

The evaluation of these subjects consists of oral examinations and the discussion of a term paper relating to the practical activities carried out all through the course.

The undergraduates who are studying these subjects are at the same time carrying out research work which ends in the tenth semester with the discussion of a diploma paper.

The Faculty of Biology also offers postgraduate courses and PhD to national and foreign postgraduates.

iii

Brazil commerates Chagas on a banknote

Teaching Intermediary Metabolism graduate Students (Poster Presentation)

LUCIA PEREIRA-DA-SILVA

Departamento de Bioqulmica UNICAMP CP 6109 13081 Campinas, SP Brasil

to Under-

Introduction The task of teaching Biochemistry is not an easy one, because usually students tend to see this discipline as a rather boring one, and especially the metabolic pathways. Many of them simply try to learn the reactions sequences and repeat them by heart when tested. Furthermore, understanding intermediate metabolism as a whole be- comes much more difficult when carbohydrate, lipid and protein metabolism are treated separately, often taught by different persons. In the end, perhaps someone gives one or two classes on the integration of metabolism, as is sometimes done in the new biochemistry textbooks. This behaviour is consistent with a reductionist point of view, but this is, in my opinion, quite inadequate for giving a good overview and encouraging understanding of Bio- chemistry.

Textbooks If we take a look in the biochemistry textbooks we observe that many of them start intermediate metabolism with a chapter dedicated to the principles of bioenergetics including some thermodynamics concepts, followed by glycolysis, the Krebs cycle, the respiratory chain and oxidative phosphorylation, other important pathways of carbohydrate metabolism and then oxidation of fatty acids and amino acids. From my experience over 20 years of dealing with Medicine, Chemistry, Biology and Phys- ical Education undergraduate students, I became aware that they usually tend to understand the Krebs cycle as being one of the pathways for the oxidation of carbo- hydrates, mainly glucose, despite all later efforts to show the relationship of this central pathway with lipid and protein catabolism. Things get worse when we reach oxidative phosphorylation, because when we show the redox chain of reactions, few students are able to recognize which substrates will be the hydrogen donors to the intermediates of the respiratory chain.

Alternative approach After thinking a lot about these problems, I decided to try a different sequence for teaching these subjects and I planned a simplified metabolic map (Fig 1). I decided to start every class showing this simple, overall metabolic scheme, pointing out which pathway we were going to study that day and correlating it with the other catabolic routes we had already covered. In the altered sequence, I presented first the oxidative production of ATP as a consequence of redox reactions in biological systems, the

BIOCHEMICAL EDUCATION 18(4) 1990

G L Y C O L Y S I S

Lactate ,I

Starch Glycogen Triacylglycerols

,oLse G,uo!Z¥,? e°°'''is A Glucose-6-P ~ - O x i d a t i o n

C02 / ' ~ , . I Pyruvate ~--- A cetyl -CoA f Oxidat ive ~ 2 H \ 4 H

J deca r b o x y l a t ~ / ~ ~

/ / / ~ wk ~ HzO [ / [ . . . . . ~ . 2 H ~ ' ~ " ~ Respiratory electron f | / I ~.~ uu~. I ~ " ~ transfer chain _ [

Ket° acids "=~ds '~ Gluta m ate " ' ~ t " ' ~ 2 H / P h °~Ph~r~'rat i ° n X

T r a n ~ a t i o n ~ A D P + Pi ~'I'P

Amino acids a-Ketoglutarate

T Proteins

Fig 1 Summary of catabolism

respiratory chain and its relation to the Krebs cycle and with all other main oxidative pathways. Only then did we begin to study particular metabolic pathways for the oxidation of carbohydrates, lipids and proteins.

I pointed out the following metabolic strategies: (1) The central aim of intermediary metabolism is the transformation of the energy obtained from nutrients for use as an energy source in biosynthetic pathways. (2) The majority of the ATP is produced through oxidative phosphorylation coupled to electron transfer in the respiratory chain. (3) Electron transfer occurs in redox reactions. Therefore students must learn how to identify the redox substrates, knowing that 02 is the final oxidant in the aerobic pathways.

Before showing the traditional respiratory chain scheme, it proved very useful to give examples of redox reactions from different metabolic pathways, instead of simply indicating a generic hydrogen donor. I selected two different redox reactions from the Krebs cycle:

181

one from the oxidation of amino acids,

CO0- glutamate COO I dehydrogenose l

H~.- -% f = o CHz + H20 + NAD( P) * = NAD(P)H+H + + CIHZ + NH, COO ~ . I / CC~-

respiratory a - keto - gLutorate glutamate chain

and one from the carbohydrate catabolism

glycerol-- P H~ C I - OH dehydrogenase /

HzCOH C = 0 HCOH" + FAD • FADHz + J

HzC--O- PO~" - _ - - H z C - O - - PO~- respiratory chain

glycerol -- phosphate di hydroxyocetone - phosphate

The reactions above illustrate electron transfer from intermediates of different metabolic pathways and the respective respiratory chain components (NADH, FADH2). At this point the student is now ready to understand the traditional scheme of the respiratory chain and the correlation of these reactions with oxidative ATP production. The interrelationships of the Krebs cycle, 13- oxidation, acetyl-CoA production from pyruvate and amino acid oxidation with the intermediates of the respiratory chain now become clear, and we are able to study the main catabolic pathways in more detail. The general metabolic scheme presented in Fig 1 was used throughout the classes to reinforce these ideas.

Conclusion Comparing the students' performance in the tests after using this strategy to teach the metabolic pathways it became clear that this simplified scheme and sequence enabled students to achieve a much better understanding of intermediary metabolism and its significance. The new scheme also helped them to get better grades as con- sequence of their improved biochemistry skill and assimil- ation.

COO COO I I CH z succmatl., CH I dehyarogenase II

CH2 + FAD F~DH z + I-IC I x . / " l COO ~ ~ -- ~ ~ CO0 -

respirator y succinate chain fumarole

CO0- CO0- 1 malone

HO - CH dehydroge~se C= 0

I CIHZ CHz + NAO + ~NADH + H ÷ + ~. / COO-

malate respiratory oxaLoacetote chain

one from the 13-oxidation of fatty acids:

0 ocyL - CoA dehydrogenose

R--CHz- CHz--CHz--C SCoA + FAD = FADHz +

fatty ocyt COA respiratory c~oin

R--CH~- CH= CH--C ~O ~SCoA

z L~ - irons -- efloyl - COA

BIOCHEMICAL EDUCATION 18(4) 1990

Papaya - - a well-known biochemical fruit on sale in Brazil