Beta-oxidation pathway steps

To some extent this may be subjective, imposing a human interpretation on the observations, but it also reflects an objective reality some reactions carry a greater flux of metabohtes than others, some are active in a wider range of cell types than others, and so on. To understand the entire chart, therefore, it is useful to collect the reactions into groups of transformation sequences known as metabolic pathways. The number of steps considered to be one pathway can be very small if very few steps are needed to convert one important metabolite into another. For example, serine biosynthesis is a three-step pathway, in which the aminoacid serine is synthesized from 3-phosphoglycerate. At the other extreme, beta-oxidation, the process that converts fatty acids from the form in which they are stored in fat cells into the form in which they are metabolically active, involves seven repetitions of the same four types of step, making an unbranched pathway of nearly 30 reactions. 

Conversely, extra-framework tin(iv) oxide nanoparticles on Si-Beta as well as Zr-, Ti-, Hf- and Al-Beta samples did not catalyse the formation of the lactone to a significant extent. As sketched in Scheme 21.9, the proposed reaction pathway with the tin catalysts involves a set of successive steps tin-enolate and carbon-carbon bond formation, proton transfer, dehydration, and cyclisation to afford the lactone. 

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