To determine which chemical equation properly shows the conversion between [tex]\(NADP ^{+}\)[/tex] and NADPH, it's important to understand the roles and chemical transformations involved.
In biological systems, [tex]\(NADP ^{+}\)[/tex] (Nicotinamide adenine dinucleotide phosphate) acts as an electron acceptor, while NADPH acts as an electron donor. The conversion from [tex]\(NADP ^{+}\)[/tex] to NADPH involves the addition of electrons and protons:
[tex]\[
NADP ^{+} + 2e^- + H ^{+} \rightarrow NADPH
\][/tex]
Here, [tex]\(2e^-\)[/tex] stands for the two electrons, and [tex]\(H ^{+}\)[/tex] is a proton. For simplicity in many biochemical contexts, the electrons are often implied, and the reaction is frequently written as:
[tex]\[
NADP ^{+} + H ^{+} \rightarrow NADPH
\][/tex]
Now let's analyze the provided choices:
A. [tex]\(NADP ^{+} + P \rightarrow NADPH\)[/tex]
- This option suggests the addition of a phosphate group, which is incorrect since [tex]\(P\)[/tex] (phosphate) is not involved in the reduction of [tex]\(NADP ^{+}\)[/tex] to NADPH.
B. [tex]\(NADP ^{+} + H ^{+} \rightarrow NADPH\)[/tex]
- This correctly shows that [tex]\(NADP ^{+}\)[/tex] gains a proton [tex]\(H ^{+}\)[/tex] to form NADPH. Therefore, this is the correct equation.
C. NADPH + ADP \rightarrow [tex]\(NADP ^{+} + ATP\)[/tex]
- This equation describes a different reaction involving energy carriers (ATP and ADP), but it doesn't show the direct conversion between [tex]\(NADP ^{+}\)[/tex] and NADPH.
D. [tex]\(NADPH + ATP \rightarrow NADP ^{+} + H ^{+}\)[/tex]
- This equation is incorrect because [tex]\(NADPH\)[/tex] and ATP do not react to form [tex]\(NADP ^{+}\)[/tex] and [tex]\(H ^{+}\)[/tex] in the same way. Moreover, the equation suggests that adding [tex]\(ATP\)[/tex] would oxidize NADPH back to [tex]\(NADP ^{+}\)[/tex].
Therefore, the correct answer is:
B. [tex]\(NADP ^{+} + H ^{+} \rightarrow NADPH\)[/tex]
