$$\begin{aligned} 3 \mathrm{CO}_2+9 \mathrm{ATP}+6 \mathrm{NADPH}+\text { water } \longrightarrow & \text { Glyceraldehyde } 3-\text { phosphate } \\ + & 9 \mathrm{ADP}+6 \mathrm{NADP}^{+}+8 \mathrm{Pi} . \end{aligned}$$
Analyse the above reaction and answer the following questions
(a) How many molecules of ATP and NADPH are required to fix one molecule of $\mathrm{CO}_2$ ?
(b) Where in the chloroplast does this process occur?
(a) 2 molecules of ATP for phosphorylation and two molecules of NADPH for reduction are required per $\mathrm{CO}_2$ molecule fixed.
(b) The calvin cycle occurs in the stroma of the chloroplast.
Some of these terms/chemicals are associated with the $\mathrm{C}_4$ cycle. Explain.
(a) Hatch Slack pathway
(b) Calvin cycle
(c) PEP carboxylase
(d) Bundle sheath cells
The terms associated with $\mathrm{C}_4$ cycle are
Hatch Slack Pathway The process of synthesis of glucose in $\mathrm{C}_4$ plants is different from $\mathrm{C}_3$ plants which was discovered by two scientists MD Hatch and CR Slack (1977). Hence, named Hatch Slack pathway.
PEP Carboxylase It is an enzyme present in mesophyll cells of $\mathrm{C}_4$ plants. It fixes $\mathrm{CO}_2$ to form 4-carbon compound, i.e., oxaloacetate (OAA).
Bundle Sheath Cells These are specialised sclerenchymatous cells present arround the vascular bundle, in the veins of monocot leaves. These have agranal chloroplast. $\mathrm{C}_3$ cycle occurs in these cells to manufacture glucose in $\mathrm{C}_4$ plants.
Calvin Cycle This cycle operates in bundle sheath cells and fixes $\mathrm{CO}_2$ to form glucose molecules.
ATP synthase enzyme has two parts
(a) $\mathrm{F}_1$-head piece is a peripheral membrane protein complex and contain the site for synthesis of ATP from ADP + pi (inorganic phosphate).
(b) $\mathrm{F}_0$-integral membrane protein complex that forms the channel through which proton cross the inner membrane.
The arrangment of $\mathrm{F}_1$ and $\mathrm{F}_0$ in thylakoid membrane is as follaws
$\mathrm{F}_0$-portion is present within the thylakoid membrane.
$\mathrm{F}_1$-portion of ATP synthase enzyme is present in the stroma if chloroplast. The conformational change occurs in $\mathrm{F}_1$ portion of ATP synthase thus, facilitaling the ATP synthesis.
