Final answer:
NADP+ is referred to as "reduced" when it gains electrons to become NADPH, as the reduction in biochemistry means the gain of electrons. This process is a key part of cellular metabolism and energy transformation during photosynthesis.
Step-by-step explanation:
When NADP+ at the end of the Electron Transport Chain gains electrons to become NADPH, it is referred to as "reduced". This is because in biochemical terms, reduction refers to the gain of electrons by a molecule, atom, or ion. It is part of the oxidation-reduction (redox) reactions that occur in cellular processes, where a reduction happens simultaneously with an oxidation – the loss of electrons. In the context of photosynthesis, NADP+ accepts electrons (and typically a proton), which reduces it to NADPH. This reduction reaction is a key step in the conversion of energy.
The terms oxidized and reduced are used to describe the transfer of electrons between molecules during metabolic processes. NADP+ is the oxidized form, while NADPH is the reduced form that carries energy-rich electrons. These electrons are ultimately used to reduce carbon dioxide in the Calvin cycle, thus playing a crucial role in transforming light energy into chemical energy via photosynthesis.