Photophosphorylation is the process by which ATP is created using energy from sunlight. It involves the creation of a proton gradient across a membrane via the electron transport chain, similar to respiration. However, since the proton gradient formation is light-dependent, it is called photophosphorylation. Proton movement across the membrane powers ATP synthase enzymes to join ADP and Pi to make ATP.

1. Photophosphorylation
Carissa Fletcher

2. Photophosphorylation is the process of
creating ATP using a Proton gradient
created by the Energy gathered from
sunlight.
The process of creating the Proton gradient
resembles that of the electron transport
chain of Respiration.
But since formation of this proton gradient is
light-dependent, the process is called
Photophosphorylation.

3. Chemiosmosis
Chemiosmosis - Chemiosmosis is the process of
using Proton movement to join ADP and Pi.
This is accomplished by enzymes called ATP
synthases.
As protons pass through this enzyme ADP and Pi
are joined to make ATP.
The movement of the Protons through this enzyme
provides the Energy needed to make

4. ATP Synthase
http://www.uic.edu/classes/bios/bios100/lectures/ps01.htm

5. Hydrogen pumping
http://www.uic.edu/classes/bios/bios100/lectures/ps01.htm

6. H+ ion gradient
• Electrons leaving photosystem II are transferred transferred through a series of
molecules and ultimately end up transferred to to a molecule called plastoquinone
(PQ).
• The PQ reacts with two hydrogen ions from the stroma and the two electrons from
photosystem II to form PQH2.
2H+stroma + 2e- + PQ  PQH2
• The PQH2 diffuses across the thylakoid membrane, passes the two electrons to the
next electron carrier and releases the two hydrogen ions into the lumen.
PQH2 PQ + 2H+lumen + 2e-
• PQ can then diffuse back across the membrane to repeat the process. The net result
of the cycle is to move two hydrogen ions from the stroma to the lumen
• THUS CREATING A GRADIENT

7. H+ ion gradient
• Electrons leaving photosystem II are transferred transferred through a series of
molecules and ultimately end up transferred to to a molecule called plastoquinone
(PQ).
• The PQ reacts with two hydrogen ions from the stroma and the two electrons from
photosystem II to form PQH2.
2H+stroma + 2e- + PQ  PQH2
• The PQH2 diffuses across the thylakoid membrane, passes the two electrons to the
next electron carrier and releases the two hydrogen ions into the lumen.
PQH2 PQ + 2H+lumen + 2e-
• PQ can then diffuse back across the membrane to repeat the process. The net result
of the cycle is to move two hydrogen ions from the stroma to the lumen
• THUS CREATING A GRADIENT