The number of chlorophyll molecules arranged per reaction centre in the light-harvesting complex is approximately:

Intact chloroplasts from green leaves can be isolated by using:

Identify $X$ and $Y$ from the figure.
$X$ $-$ $Y$

In a chlorophyll $a$ molecule,which of the following groups is attached to carbon atom $3$ of pyrrole ring $II$?

In the figure given below,the black line (upper) indicates the action spectrum for photosynthesis and the lighter line (lower) indicates the absorption spectrum of chlorophyll-$a$. Answer the following:
$(a)$ What does the action spectrum indicate? How can we plot an action spectrum? Explain with an example.
$(b)$ How can we derive an absorption spectrum for any substance?
$(c)$ If chlorophyll-$a$ is responsible for the light reaction of photosynthesis,why do the action spectrum and absorption spectrum not overlap?

Identify the correct sequence of pigments based on their molecular weight (from higher to lower).