Examine the figure
(a) Is this struture present in animal cell or plant cell?
(b) Can these be passed on to the progeny? How?
(c) Name the metabolic processes taking place in the places marked ( $A$ ) and (B).
(a) The above figure show the chloroplast which is green in colour and performs photosynthesis in plants thus, The structure is present in plant cell.
(b) Yes, chloroplast has the power of self replication because of presence of extranuclear DNA.
(c) The metabolic that occurs in the marked places are as follows. A-It is the stroma of chloroplast where dark reaction of photosynthesis takes place.
$B$-It is the structure of extra nuclear DNA and is responsible for replication of chloroplast, when it is required in the photosynthesising cells.
$$2 \mathrm{H}_2 \mathrm{O} \rightarrow 4 \mathrm{H}^{+}+\mathrm{O}_2+4 e^{-}$$
Based on the above equation, answer the following questions
(a) Where does this reaction take place in plants?
(b) What is the significance of this reaction?
(a) The reaction takes place in reaction centre PS II, located on the inner surface of thylakoid membrane. It is known as water splitting centre where electrons are extracted from water. The $\mathrm{Mn}^{+}$and $\mathrm{Cl}^{-}$ions catalyse this reaction.
(b) Splitting of water is an important event in photosynthesis as
(i) It releases molecular oxygen as byproduct of photosynthesis and is the significant source of oxygen in air, or is essential for all living beings on earth.
(ii) Hydrogen ions produced, are utilised in reducing NADP to NADPH, a strong reducing agent.
(iii) The electrons released are transferred from PS II to PS I through a series of electron carriers thus, creating a gradient for the synthesis of ATP.