Photosynthesis (College Board AP® Biology)

The light-independent reactions of photosynthesis, also known as the Calvin cycle, occur in the stroma of the chloroplast and are responsible for producing complex organic molecules. Which of the following correctly describes an event that occurs during the Calvin Cycle?

DCPIP is a chemical compound that is blue when oxidised and colourless when it accepts electrons during the light-independent reaction. Figure 1 shows the experimental set-up of a study that investigates the effect of ammonium hydroxide on the photosynthetic activity of chloroplasts that have been extracted from spinach leaves and suspended in an isolation medium.  All five tubes are placed in a water bath at 20 °C and illuminated from all sides during the investigation.

Which tube in Figure 1acts as a control that allows the effect of ammonium hydroxide to be clearly determined?

Photosynthetic pigments, such as chlorophyll a, chlorophyll b and carotenoids, absorb light energy during photosynthesis. Different pigments absorb light at different wavelengths, as shown in Figure 1.

Which of the following correctly describes the absorption data shown in Figure 1?

The evolution of photosynthesis in prokaryotic organisms transformed the Earth's atmosphere and allowed for the development of complex life. Scientists claim that the first early photosynthetic organisms, known as cyanobacteria, evolved around 2.3 billion years ago. Which of the following graphs provides evidence for this?