The main aims of this programme are to show how the pathways involved in the biosynthesis of terpenes and steroids have been established, and to illustrate some of the techniques used in tackling b...iosynthetic problems. This programme concentrates on one particular group of natural products, the terpenes. The first part of the programme looks at the way in which biosynthetic precursors of the terrenes were proposed over a period of some seventy years and how their connections with another group of substances called steroids were established. You will see how the painstaking work of a great many scientists was necessary to elucidate the biogenetic precursors of cholesterol. The latter part of the programme takes you right into the teeth of a research problem facing Dr. Barrie Charlwood and his colleagues, Dr. D. V. Banthorpe and Dr. M. R. Young, working at the Christopher Ingold Laboratories, University College, London, in 1972. This was a problem concerned with a possible threat to the unified scheme discussed earlier and the need to see whether the biosynthesis of the cyclic monoterpene, pulegone, fitted in or not. In this part of the programme Dr. Charlwood describes his research and how radioactive tracers were used to solve the problem.
|S24-; 11; 1973
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|Len Haynes; David Roberts
|BBC Open University
|Acetic acid; Biodegeneration; Biosynthesis; Carbon compounds; Carbon cycle; Fat formation; Fatty acids; Photosynthesis; Protein from mineral oil
|Len Haynes introduces the programme. D.R.Roberts gives the historical background to the Isoprene Rule. He looks at the way in which biosynthetic precursors of the terpenes were proposed over a period of some 70 years and how their connections with another group of substances called steroids were established. Diagrams aid his discussion. Haynes explains how the idea that mevalonic acid may be a precursor of cholesterol was formed. Roberts with the aid of animated diagrams explains the biosynthesis of cholesterol from the precursor mevalonic acid. Haynes explains why laboratory research is crucial in determining biosynthetic pathways. B.V. Charlwood describes his research which tried to determine if the monoterpene pulegone fits into the unified scheme for biosynthesis of terpenes and steroids. With a series of diagrams he examines the proposed pathway from mevalonic acid to pulegone using radio-active labelled 14C in a plant. Film shots of the actual experiment in which 14C labelled mevalonic acid was fed to the plant mentha pulegium (Penny Royal) and pulegone was isolated after biosynthesis. Haynes explains why the pulegone product above had to be so thoroughly purified and then poses the questions- how is it possible to tell if the mevalonic acid was not first broken down to simpler substances which were then biosynthesised to pulegone. Charlwood explains his method of chemical degradation which was used to show that mevalonic acid was not first broken down. The laboratory technique is shown. Charlwood then uses a series of diagrams to aid his discussion.
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