Which of the following accurately reflects the overall free energy change in a biosynthetic pathway?

The accurate reflection of the overall free energy change in a biosynthetic pathway is that individual steps may be unfavorable. In biochemical pathways, including biosynthetic pathways, it's important to recognize that the overall pathway can be driven by the cumulative free energy changes of the individual reactions involved.

Biosynthetic pathways often include a series of coupled reactions, where the favorable (exergonic) reactions can drive the unfavorable (endergonic) ones. This coupling allows for the pathway as a whole to be energetically favorable, even if some individual steps might have a positive free energy change. Therefore, while certain steps in the pathway may require energy input or be thermodynamically unfavorable, the pathway can still proceed due to the net effect of the overall free energy change, which can be negative when considering all reactions together.

Understanding this principle is essential for grasping how complex metabolic pathways function, as it highlights the balance between favorable and unfavorable reactions in achieving the cell's synthetic goals.