Page 122 - Demo 1

Figure 54. Electron Pathway in the Light Reacons Energized electrons leave PS II and pass
down an electron transport chain, leading to the formaon of ATP by chemiosmosis.
Energized electrons (replaced from PS II) leave PS I and pass to NADP+, which then
combines with H+ to become NADPH. The electrons from PS II are replaced with
electrons from water as it splits to release oxygen. Source: https://ka-perseus-
images.s3.amazonaws.com/6cdc38a35081992a769ad3edacd1cbea02c5a306.png

3. The electron transport chain establishes an energy gradient. The
excited electron is shuled along a series of electron-carrier molecules
embedded in the membrane called the electron transport chain. As
the electron passes along the electron transport chain, the energy
from the electron is released in small amounts in the form of a
+
hydrogen ion (H ) gradient. Each me water is split, two H remain in
+
the thylakoid space. Addionally, electrons give up energy as they
move from carrier to carrier along the electron transport chain. This
+
energy is used to pump H from the stroma to the thylakoid space,
+
thus, there are many more H in the thylakoid space than in the
+
stroma and a H gradient is established.
+
The H then flow down their concentraon gradient, across the
thylakoid membrane at the ATP synthase complex, and energy is
released. The kinec energy that is released by the movement of H is
+
transferred to potenal energy in the building of ATP molecules from
ADP. This process, called chemiosmosis, produces the ATP that will
be used in the Calvin cycle to make carbohydrates.

4. PS I produces NADPH. When the PS I pigment complex absorbs solar
energy, energized electrons leave its reacon center and are captured
by a different electron acceptor. Low-energy electrons from the
electron transport system adjacent to PS II replace those lost by PS

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