Tag: photosynthesis in plants

P ${ _7}$${ _0}$${ _0}$ is the reaction center of the PS-I. So, when PS- I receives light energy electron is released by P ${ _7}$${ _0}$${ _0}$.

Photosystem II has P680 reaction center wherein oxygen atoms of two water molecules bind to a cluster of manganese atoms. These Mn atoms are bound to the reaction center and associated with an enzyme that splits water, removes electrons one at a time. These electrons fill the holes which are left in the reaction center due to released to light-energized electrons. Immediately after removal of four electrons from the two water molecules, O2 is released. The absence of PS II results in cyclic photophosphorylation by PSI that does not have water splitting complex and no oxygen is released. Phytochromes are blue-green, proteinaceous pigments that are involved in physiological responses to light. Phycocyanin is the photosynthetic pigment of cyanobacteria. Thus, the correct answer is option B.

Like most other photosynthetic bacteria, purple and green sulphar bacteria do not produce oxygen (anoxygenic), because the reducing agent (electron donor) involved in photosynthesis is not water. They use H$ _{2}$S or Elementary Sulphur as electron donor. In any photosynthetic organism, CO$ _{2}$ is not used as electron donor. Rhodopseudomonas uses isopropanol as electron donor.
So, the correct answer is option B.

There are only two photosystems PS I and PS II. Photosynthetic bacteria have only PS I and absence of PSII makes them carry out cyclic photophosphorylation wherein $H _2S$ serves as an electron donor, rather than water, and there is no release of oxygen. The low light intensity and anaerobic conditions favor cyclic photophosphorylation. The correct answer is B.

Chloroplasts are eukaryotic cell organelles. They are covered by the double membrane and also have an internal membrane system comprised of thylakoid membranes. The thylakoid membranes are of two types. The membranes which make grana are called granal lamellae. The other thylakoid membranes are called stromal membranes . The non-appressed membranes (stromal membranes and edges of granal membranes) are in direct contact with the stroma. The PS- I is abundant in non-appressed membrane whereas PS- II is abundant in granal membranes.

There are two photosystems PS I and PS II. Photosynthetic bacteria have only PS I and absence of PSII makes them carry out cyclic photophosphorylation wherein $H _2S$ serves as an electron donor, rather than water, and there is no release of oxygen. The low light intensity and anaerobic conditions favor cyclic photophosphorylation. The correct answer is A. 

There are two types of photosystems, the photosystem I (PS- I) and the photosystem II (PS II). These are the structural and functional protein components in the photosynthesis. The photosytem I is present in the green and purple bacteria that conduct the bacterial photosynthesis where as the photosystem II is present in the cyanobacteria that conduct the normal plant photosynthesis.

Ferredoxin is an iron-containing protein, associated with photosystem I. The ferredoxin accepts electrons from photosystem I and passes them to oxidized NADP to form reduced $NADPH _2$. The enzyme responsible for reduction of NADP is called as NADP ferredoxin oxidoreductase.

During photosynthesis light energy is converted to chemical energy of glucose. Light energy is absorbed by a pair of chl a molecules, of PS I or PS II, this excited chl a molecule releases one e$^-$, that moves through the ETS of the PSI and PSII releasing energy at each level during the transport, used for the formation of ATP