In oxygenic photophosphorylation (a) photosystem II uses the photopigment bacteriochlorophyll   (b) Oxygen is used as an electron donor    (c) ATP is produced by means of substrate level phosphorylation                                          (d) photosystem I reduces NADP    (e) none of the above

Melvin Calvin and Andrew Benson determined the steps in the light-independent reactions of photosynthesis by exposing the green alga Chlorella to CO2 labeled with the radioisotope carbon 14. By looking at which compounds the C14 ended up in, they were able to identify all intermediates in this cyclic pathway. Why did they predict correctly that the same set of intermediates would be formed in the light reaction in land plants?

Photosynthesis directly opposes respiration in determining how plants influence atmospheric CO2 concentrations. When a leaf is in the light, both photosynthesis and respiration are occurring simultaneously. The data in the Table were collected from the leaf of a sagebrush plant that was enclosed in a chamber that measures the rate of CO2 exchange. The same leaf was used to collect the data in Interpret the Data in Chapter 7. Respiration is shown as a negative and photosynthesis as a positive rate of CO2 exchange. The net photosynthesis rate is the amount of CO2 (in micromoles per square meter per second) assimilated by the leaf while respiration is occurring; a positive value indicates more photosynthesis is occurring than respiration. The light exposed to the leaf is quantified as the number of photons in the 400 to 700 nm wavelength, the photosynthetic photon flux density (PPFD); 2,000 mol/m2/s is equivalent to the amount of light occurring at midday in full Sun. Observation Photosynthetic Photon Flux Density (PPFD) (mol/m2/s) Net Photosynthesis (mol/m2/s) 1 2,000 9.1 2 1,500 8.4 3 1,250 8.2 4 1,000 7.4 5 750 6.3 6 500 4.8 7 250 2.2 8 0 -2.0 Why is net photosynthesis negative when PPFD is zero? Looking at the respiration data from Interpret the Data in Chapter 7, at what temperature do you think these data were collected? Source: Data based on unpublished research by Brent Ewers, University of Wyoming.

Describe the flow of electrons through photosystems I and II in the noncyclic electron transport pathway and the products produced. Contrast this flow with cyclic electron transport.