Question

Choose the correct statement:

• A. $\mathrm{NADH}$ produced in light reaction is used for reduction of ${\mathrm{CO}}_2$
• B. Reduction of $\mathrm{NAD}$ to $\mathrm{NADH}$ occurs in Calvin cycle
• C. S. Ochoa showed ${\mathrm{NADP}}^{+}$ is the biological electron acceptor in the chloroplast
  
• D. Fixation and reduction of ${\mathrm{CO}}_2$ requires $\mathrm{ATP}$, $\mathrm{NADPH}$ and light

Answer 1

The correct option is C S. Ochoa showed ${\mathrm{NADP}}^{+}$ is the biological electron acceptor in the chloroplast


Light reaction in photosynthesis produces $\mathrm{ATP}$ and reduces ${\mathrm{NADP}}^{+}$ to $\mathrm{NADPH}$.

Robert Hill showed that when isolated chloroplast was illuminated with light, it could only produce oxygen if any suitable electron acceptor is present.

Later on, S. Ochoa showed that ${\mathrm{NADP}}^{+}$ is the biological electron acceptor in the chloroplast. $\mathrm{NADPH}$ gets oxidised by donating its electron in the Calvin cycle.

Calvin cycle is the carbon fixation phase where ${\mathrm{CO}}_2$ is reduced using $\mathrm{NADPH}$ and $\mathrm{ATP}$. This phase doesn't need light and hence, is called a dark reaction.