Problem 11
What are the light-dependent changes in the stroma that regulate the Calvin cycle?
Problem 12
When one equals two. In the \(\mathrm{C}_{4}\) pathway, one ATP molecule is used in combining the \(\mathrm{CO}_{2}\) with phosphoenolpyruvate to form oxaloacetate, but, in the computation of energetics bookkeeping, two ATP molecules are said to be consumed. Explain.
Problem 14
What is photorespiration, what is its cause, and why is it believed to be wasteful?
Problem 15
Why do high concentrations of \(\mathrm{CO}_{2}\) inhibit photorespiration?
Problem 16
\(\mathrm{C}_{3}\) plants are most common in higher latitudes and become less common at latitudes near the equator. The reverse is true of \(\mathrm{C}_{4}\) plants. How might global warming affect this distribution?
Problem 17
\(\mathrm{C}_{3}\) plants require 18 molecules of ATP to synthesize 1 molecule of glucose. \(C_{4}\) plants, on the other hand, require 30 molecules of ATP to synthesize 1 molecule of glucose. Why would any plant use \(\mathrm{C}_{4}\) metabolism instead of \(\mathrm{C}_{3}\) metabolism given that \(\mathrm{C}_{3}\) metabolism is so much more efficient?
Problem 18
Rubisco catalyzes both a carboxylation reaction and a wasteful oxygenase reaction. Below are the kinetic parameters for the two reactions. $$\begin{array}{cccc}\hline K_{\mathrm{M}}^{\mathrm{CO}_{2}}(\mu \mathrm{M}) & K_{\mathrm{M}}^{\mathrm{O}_{2}}(\mu \mathrm{M}) & K_{\mathrm{cat}}^{\mathrm{CO}_{2}}\left(\mathrm{s}^{-1}\right) &K_{\mathrm{cat}}^{\mathrm{O}_{2}}\left(\mathrm{s}^{-1}\right) \\\10 & 500 & 3 & 2 \\\\\hline\end{array}$$ (a) Determine the values of \(k_{\text {cat }}^{\text {CO }_{2} / K_{M}^{\text {CO }_{2}} \text { and } k_{\text {cat }}^{\mathbf{O}_{2}} / K_{M}^{\mathbf{O}_{2}}}\) as \(s^{-1} M^{-1}\).
Problem 20
Use the following information to estimate the efficiency of photosynthesis. The \(\Delta G^{\text {o\prime }}\) for the reduction of \(\mathrm{CO}_{2}\) to the level of hexose is \(+477 \mathrm{kJ} \mathrm{mol}^{-1}\left(+114 \mathrm{kcal} \mathrm{mol}^{-1}\right)\)' A mole of 600 -nm photons has an energy content of \(199 \mathrm{kJ}(47.6 \mathrm{kcal})\) Assume that the proton gradient generated in producing the required NADPH is sufficient to drive the synthesis of the required ATP.
Problem 23
An illuminated suspension of Chlorella, a genus of single-celled green algae, is actively carrying out photosynthesis. Suppose that the light is suddenly switched off. How will the levels of 3 -phosphoglycerate and ribulose 1,5-bisphosphate change in the next minute?
Problem 24
An illuminated suspension of Chlorella is actively carrying out photosynthesis in the presence of \(1 \%\) \(\mathrm{CO}_{2} .\) The concentration of \(\mathrm{CO}_{2}\) is abruptly reduced to \(0.003 \% .\) What effect will this reduction have on the levels of 3-phosphoglycerate and ribulose \(1,5-\) bisphosphate in the next minute?
