The substance dichlorophenyldimethylurea (DCMU) is an herbi- cide that inhibits photosynthesis by blocking electron transfer between plastoquinones in photosystem II. (a) Would you expect DCMU to interfere with cyclic photophos- phorylation? (b) Normally, DCMU blocks Oz evolution, but addition of ferri- cyanide to chloroplasts allows Oz evolution in the presence of DCMU. Explain.

The substance dichlorophenyldimethylurea (DCMU) is an herbi- cide that inhibits photosynthesis by blocking electron transfer between plastoquinones in photosystem II. (a) Would you expect DCMU to interfere with cyclic photophos- phorylation? (b) Normally, DCMU blocks Oz evolution, but addition of ferri- cyanide to chloroplasts allows Oz evolution in the presence of DCMU. Explain.

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter9: Photosynthesis: Capturing Light Energy

Section9.2: Chloroplasts

Problem 2C: What is the significance that the combined absorption spectra of chlorophylls a and b roughly match...

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The substance dichlorophenyldimethylurea (DCMU) is an herbicide thatinhibits photosynthesis by blocking electron transfer between plastoquinones in photosystem II.(a) Would you expect DCMU to interfere with cyclic photophosphorylation?(b) Normally, DCMU blocks O2 evolution, but addition of ferricyanide to chloroplasts allows O2 evolution in the presence of DCMU. Explain.
1) Dichlorophenyldimethylurea inhibits photosynthesis by blocking electron transfer between the plastoquinone in photosystem II. a) Would you expect this to interfere with cyclic photophosphorylation? b) This herbicide normally stops O2 evolution, but if we add ferricyanide to the chloroplasts, O2 evolution continues. Why might this be the case?
The substance dichlorophenyldimethylurea (DCMU) is an herbicide thatinhibits photosynthesis by blocking electron transfer between plastoquinonesin photosystem II.(a) Would you expect DCMU to interfere with cyclic photophosphorylation?(b) Normally, DCMU blocks O2 evolution, but addition of ferricyanide tochloroplasts allows O2 evolution in the presence of DCMU. Explain.
In 2010, a bew form of chlorophyll (chlorophyll f) was discovered in cyanobacteria assemblages of stromatolites growing in Shark Bay, Australia. Chlorophyll f has been isolated. and scientists are investigating the structure and function of this pigment. Based on your understanding of photosynthesis, how would you determine the wavelengths of light the pigment absorbs? How would you determine if this pigment plays a role in photosynthesis? (Hint: Think about the overall equation for photosynthesis.)
Why do we describe the path of electrons in photosynthesis as starting in photosystem II and ending in photosystem I? In other words, why is the nomenclature “backward”
Why would nature evolve a key enzyme, rubisco, that is so sensitive to oxygen, resulting in photorespiration?
In photosynthesis, contrast the light reactions with the light independent reactions, in terms of goals, inputs, and outputs of each. Spatially where do they take place (which parts of the chloroplast)? (Optional, for further discussion: Could there be light reactions without light-independent reactions, or visa-versa?)
There are two photosystems ( I and II) involved in the light-dependent reactions of photosynthesis. What is the functional difference between these two photosystems?
For most plants, two distinct photosystems (Photosystem I and Photosystem II) work together in series during photosynthesis. These photosystems are complexes of proteins and pigment molecules. Statement 1: Photosystem I has an absorption maximum of 680 nm, whereas Photosystem II has an absorption maximum of 700 nm. Statement 2: The special pair of chlorophyll a molecules in the reaction center of photosystem I is designated as P700, whereas the special pair of chlorophyll a molecules in the reaction center of photosystem II is designated as P680. Statement 1 is true. Statement 2 is false. Statement 1 is false. Statement 2 is true. Both statements are true. Both statements are false.
What is implied about the energyrequirements of photosystems I and II by the fact that there is a difference in the minimum wavelength of light needed for them tooperate (700 nm for photosystem I and 680 nm for photosystem II)?
In terms of the spatial organization of photosynthesis within the chloroplast, what is the advantage of the light reactions producing NADPH and ATP on the stroma side of the thylakoid membrane?
Which of the mechanisms for dissipating light energy shown in Fig. would best protect the photosystems from excess light energy?