The first reactants of a metabolic pathway are called substrates, while the end products of the pathway are called products. In the sequence A--B--C--D,D branching into 2 parts E and F. So, the correct answer would be A represents reactant and E and F end products.
In general, in a metabolic pathway, the substrates refer to the initial reactants that undergo a series of enzymatic reactions, eventually leading to the formation of end products.
The substrates are the molecules that enter the pathway and undergo specific transformations through enzymatic reactions. They serve as the starting materials for the pathway. As the reactions progress, the substrates are modified and converted into intermediate compounds, eventually leading to the formation of the final products.
The end products, as the name suggests, are the final molecules or compounds that are produced as a result of the metabolic pathway. These products can serve as important molecules for cellular processes, and energy production, or be utilized for further biochemical reactions in the cell.
In the figure A--B--C--D branching into E and F, A represent(s) the first reactant(s) of this metabolic pathway and E and F represent(s) the end product(s) of this pathway.
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