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A Handbook of Biology
2. SPLÏTTÏÑG ØF WÅTËR (PHØTØLÝSÏS)
The water splitting complex in PS II is located on the inner side of the
thylakoid membrane.
Water is split into H+, [O] and electrons.
2H2O ® 4H+ + O + 4e−
These electrons are needed to replace the electrons that are moved
from PS II
The protons (H+) are used to reduce NADP to NADPH.
Oxygen is liberated as a by-product of photosynthesis.
PS II provides electrons needed to replace those removed from PS I.
3. PHØTØ-PHØSPHØRÝLÅTÏØÑ
The synthesis of ATP by cells (in
mitochondria & chloroplasts) is
called phosphorylation.
Photo-phosphorylation
is
the
synthesis of ATP from ADP in
chloroplasts in presence of light.
It occurs in 2 ways: Non-cyclic
and Cyclic.
Photosystem I
Light
e-acceptor
Electron
transport
system
Chlorophyll
P 700
ADP+iP
ATP
Å) ÑØÑ-ÇÝÇLÏÇ PHØTØ-PHØSPHØRÝLÅTÏØÑ
It
occurs
when
the
two
photosystems work in a series,
(first PS II and then PS I) through
an electron transport chain as
seen in the Z scheme.
Here, ATP & NADPH+ + H+ are
synthesised.
B) ÇÝÇLÏÇ PHØTØ - PHØSPHØRÝLÅTÏØÑ
It occurs in stroma lamellae when only PS I is functional.