Biology, Eighth Edition (Raven)

Chapter 8: Photosynthesis

Photosynthetic Electron Transport and ATP Synthesis

Is the production of ATP in photosynthesis similar to the production of ATP in cellular respiration? Photosynthesis is often described as the reverse of cellular respiration. Respiration breaks down complex molecules to release energy that is used to make ATP. Photosynthesis takes energy from photons and uses it to build complex molecules. However both systems use an electron transport chain and associated proton pump and ATP synthase as a key part of the process. In photosynthesis electrons enter the transport chain after receiving light energy – in respiration the electrons are provided by organic food molecules. In both cases the electron transport chain uses the energy to pump hydrogen ions across a membrane. The protons pass back through ATP synthase, driving the production of ATP. In photosynthesis this ATP is used to construct organic molecules from carbon dioxide and water.

View the animation below, then complete the quiz to test your knowledge of the concept.


Which of the following represents a correct sequence during photosynthesis?
A)Photosystem I - ATP production - Photosystem II - NADPH production
B)Photosystem I - NADPH production - Photosystem II - ATP production
C)Photosystem II - ATP production - Photosystem I - NADPH production
D)Photosystem II - NADPH production - Photosystem I - ATP production
E)Photosystem I - Photosystem II - ATP production - NADPH production

The electrons excited by sunlight are replaced by electrons from _______ in photosystem I, and by electrons from ________ in photosystem II.
A)water ; photosystem I
B)water ; carbon dioxide
C)water ; water
D)photosystem II ; photosystem I
E)photosystem II ; water

The high-energy electrons of photosystem I are directly passed on to
D)ATP synthase.
E)NADP reductase.

Photosynthetic pigments are clustered together to form photosystems in the stroma of the chloroplast.

Plastoquinone is the primary electron acceptor for electrons leaving photosystem II.
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