When light strikes chlorophyll molecules, they lose electrons, which are ultimately

The light reactions take place in the structures of the chloroplast called the __________, while the Calvin cycle takes place in the __________.

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 following are inputs to photosynthesis? Choose all that apply. Which are outputs? Choose all that apply. a. CO2 b. O2 c. sugar d. H2O e. light

Explain how the name photosynthesis describes what this process accomplishes.

What color of light is the least effective in driving photosynthesis? Why?

When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by splitting molecules of __________.

Which of the following are produced by reactions that take place in the thylakoids and are consumed by reactions in the stroma? a. CO2 and H2O b. NADP+ and ADP c. ATP and NADPH d. glucose and O2

The reactions of the Calvin cycle are not directly dependent on light, and yet they usually do not occur at night. Why?

Of the following metabolic processes, which one is common to photosynthesis and cellular respiration? a. reactions that convert light energy to chemical energy b. reactions that split H2O molecules and release O2 c. reactions that store energy by pumping H+ across membranes d. reactions that convert CO2 to sugar

Tropical rain forests cover only about 3% of Earths surface, but they are estimated to be responsible for more than 20% of global photosynthesis. For this reason, rain forests are often referred to as the lungs of the planet, providing O2 for life all over Earth. However, most experts believe that rain forests make little or no net contribution to global O2 production. From your knowledge of photosynthesis and cellular respiration, can you explain why they might think this? (Hint: What happens to the energy stored as sugars in the body of a plant when that plant dies or parts of it are eaten by animals?)

Suppose you wanted to discover whether the oxygen atoms in the glucose produced by photosynthesis come from H2O or CO2. Explain how you could use a radioactive isotope to find out.

Interpreting Data The graph above right is called an absorption spectrum. Each line on the graph is made by shining light of varying wavelengths through a sample. For each wavelength, the amount of that light absorbed by the sample is recorded. This graph combines three such measurements, one each for the pigments chlorophyll a, chlorophyll b, and the carotenoids. Notice that the graphs for the chlorophyll pigments match the data presented in Figure 7.5. Imagine a plant that lacks chlorophyll and relies only on carotenoids for photosynthesis. What colors of light would work best for this plant? How would this plant appear to your eye?

There is strong evidence that Earth is getting warmer because of an intensified greenhouse effect resulting from increased CO2 emissions from industry, vehicles, and the burning of forests. Global climate change could influence agriculture, melt polar ice, and flood coastal regions. In response to these threats, 192 parties have accepted the Kyoto Protocol, which calls for mandatory reductions of greenhouse gas emissions in 30 industrialized nations by 2012. The United States has signed but not ratified (put into effect) the agreement, instead proposing a more modest set of voluntary goals allowing businesses to decide whether they wish to participate and providing tax incentives to encourage them to do so. The reasons given for rejecting the agreement are that it might hurt the American economy and that some less industrialized countries (such as India) are exempted from it, even though they produce a lot of pollution. Do you agree with this decision? In what ways might efforts to reduce greenhouse gases hurt the economy? How can those costs be weighed against the costs of global climate change? Should poorer nations carry an equal burden to reduce their emissions?

Burning biomass to produce electricity avoids many of the problems associated with gathering, refining, transporting, and burning fossil fuels. Yet the use of biomass as fuel is not without its own set of problems. What challenges might arise from a large-scale conversion to biomass energy? How do these challenges compare with those encountered with fossil fuels? Which set of challenges do you think is more likely to be overcome? Does one energy source have more benefits and fewer costs than the others? Explain.