why is there an uneven distribution of photosystem 1 and 2 on the thylakoid membrane? Solution Photosynthesis is carried out by the cyanobacteria, plants involved the absorption of light and the conversion of its energy into chemical energy. The photosynthetic apparatus is made up of 4 multiprotein complexes, which are asymmetrically embedded in the thyalkoid memberane. It is the high structural and functional coordination between these 4 complexes, which enables the efficient coupling of photosynthetic electron transfer and photophosphorylation. The 4 complexes - Photosystem II (PSII), cytochrome b6f complex, PS I and the proton-ATP synthase, are unevenly distributed between the 2 regions of the thylakoids. The PS II complex is situated in the appressed grana-lamella region, the PS I and the ATP synthase complex are located in the non-appressed stroma-lamella region. Light driven electron transfer is intiated with the oxidation of water mole. by the PS II complex and the reduction of quinones associated with the PS II complex. The electrons are then transferred across the memberane to plastocyanin via the Cyt b6f complex. Plastocyanin is a copper protein facing the lumen of the thylakoids, is the secondary electron donor of the PS I complex. In the PS I the electron are translocated across the memberane to ferredoxin which further transfers them to NADP+. The membrane potental and proton gradient resulting from this photochemical electron transport provide the motive force required for the formation of ATP by the ATP synthase. The transport of electron against the electrical potential and the formation of ATP and NADPH are made possible due to the unique ability of the thylakoids to absorb light energy. The 2 pigment complexes (PS II and PS I) are responsible for harvesting the light and performing the charge separation across the thylakoid memberanes. Photosytem II (PS II): 1. PS II is located at the inner surface the grana thyalkoid memberane 2. The photocentre is P680 3. Pigments absorb shorter wavelengths of light (<680nm) 4. Participates only in non cyclic photophosphorylation 5. It is associated with photolysis of water 6. Main functions are ATP synthesis and hydrolysis of water Photosystem I (PS I) 1. PS I is located at the outer surface the grana thylakoid memberane 2. The photocentre is P700 3. Pigments absorb longer wavelength of light (>680nm) 4. Participates in cyclic and non-cyclic photophosphorylation 5. It is not associated with photolysis of water 6. Main function is ATP synthesis This is the purpose the two photosystems (PS) are unevely distributed in thyalkoid memberane..

1. why is there an uneven distribution of photosystem 1 and 2 on the thylakoid membrane?
Solution
Photosynthesis is carried out by the cyanobacteria, plants involved the absorption of light and the
conversion of its energy into chemical energy. The photosynthetic apparatus is made up of 4
multiprotein complexes, which are asymmetrically embedded in the thyalkoid memberane. It is
the high structural and functional coordination between these 4 complexes, which enables the
efficient coupling of photosynthetic electron transfer and photophosphorylation.
The 4 complexes - Photosystem II (PSII), cytochrome b6f complex, PS I and the proton-ATP
synthase, are unevenly distributed between the 2 regions of the thylakoids. The PS II complex is
situated in the appressed grana-lamella region, the PS I and the ATP synthase complex are
located in the non-appressed stroma-lamella region.
Light driven electron transfer is intiated with the oxidation of water mole. by the PS II complex
and the reduction of quinones associated with the PS II complex. The electrons are then
transferred across the memberane to plastocyanin via the Cyt b6f complex. Plastocyanin is a
copper protein facing the lumen of the thylakoids, is the secondary electron donor of the PS I
complex. In the PS I the electron are translocated across the memberane to ferredoxin which
further transfers them to NADP+. The membrane potental and proton gradient resulting from this
photochemical electron transport provide the motive force required for the formation of ATP by
the ATP synthase.
The transport of electron against the electrical potential and the formation of ATP and NADPH
are made possible due to the unique ability of the thylakoids to absorb light energy. The 2
pigment complexes (PS II and PS I) are responsible for harvesting the light and performing the
charge separation across the thylakoid memberanes.
Photosytem II (PS II):
1. PS II is located at the inner surface the grana thyalkoid memberane
2. The photocentre is P680
3. Pigments absorb shorter wavelengths of light (<680nm)
4. Participates only in non cyclic photophosphorylation
5. It is associated with photolysis of water
6. Main functions are ATP synthesis and hydrolysis of water
Photosystem I (PS I)
1. PS I is located at the outer surface the grana thylakoid memberane
2. The photocentre is P700

2. 3. Pigments absorb longer wavelength of light (>680nm)
4. Participates in cyclic and non-cyclic photophosphorylation
5. It is not associated with photolysis of water
6. Main function is ATP synthesis
This is the purpose the two photosystems (PS) are unevely distributed in thyalkoid memberane.