Electron transport powers the first steps of photosynthesis. The following diagram shows the
passage of electrons through the photosynthetic electron transport chain (ETC). a. What is the
source of the electrons (e) that enter Photosystem II (PSII)? What membrane are these
complexes embedded in? What is the final e^- acceptor for e^- leaving Photosystem I (PSI)?
(Please indicate both the unreduced and the reduced form of this acceptor) The light energy
captured by the photosynthetic reaction centers is used to establish a pH gradient across this
chloroplast membrane. (This means a gradient of H ions.) a. Indicate on the diagram above,
where the concentration of H is low and where it is high. How is this pH gradient established?
Specify at least 2 different ways. How is the H gradient (potential energy) used? What are the
products that the proton gradient made? Where in the chloroplast are they made?
Solution
Question number 1 :
A. In Higher plants, the ultimate source of the electrons passed to NADPH in plant (oxygenic)
photosynthesis is water. Photosynthetic bacteria use a variety of electron donors for this purpose
acetate, succinate, malate, or sulfide depending on what is available in a particular ecological
niche.
B. These photosystems are embedded in the thylokoid membranes. Higher plants contsins two
types of photosynthetic units associated with two different pigment systems, whcih obsorbs light
of different wavelengths.
C. The final electron acceptor in photosynthesis is NADP+, which is reduced to NADPH by
NADP reductase..
Electron transport powers the first steps of photosynthesis. The fo.pdf
1. Electron transport powers the first steps of photosynthesis. The following diagram shows the
passage of electrons through the photosynthetic electron transport chain (ETC). a. What is the
source of the electrons (e) that enter Photosystem II (PSII)? What membrane are these
complexes embedded in? What is the final e^- acceptor for e^- leaving Photosystem I (PSI)?
(Please indicate both the unreduced and the reduced form of this acceptor) The light energy
captured by the photosynthetic reaction centers is used to establish a pH gradient across this
chloroplast membrane. (This means a gradient of H ions.) a. Indicate on the diagram above,
where the concentration of H is low and where it is high. How is this pH gradient established?
Specify at least 2 different ways. How is the H gradient (potential energy) used? What are the
products that the proton gradient made? Where in the chloroplast are they made?
Solution
Question number 1 :
A. In Higher plants, the ultimate source of the electrons passed to NADPH in plant (oxygenic)
photosynthesis is water. Photosynthetic bacteria use a variety of electron donors for this purpose
acetate, succinate, malate, or sulfide depending on what is available in a particular ecological
niche.
B. These photosystems are embedded in the thylokoid membranes. Higher plants contsins two
types of photosynthetic units associated with two different pigment systems, whcih obsorbs light
of different wavelengths.
C. The final electron acceptor in photosynthesis is NADP+, which is reduced to NADPH by
NADP reductase.
