Photosynthetic Stages

1. Explain how CO2 enters leaves. What environmental factors control stomatal movement? How are these factors related to physical and chemical properties that control the opening and closing of stomata?

When it comes to entering the leaves CO2 gains access to the leaves through tiny holes present in the leaves called the stomata. The environmental factor which controls stomatal movement is the intensity of light. When light is present the photosynthesis process takes place, calling for more CO2, therefore making the stomata opening more open. During darkness the openings are smaller and serve as a release for excess CO2.

1. What are primary stages in the photosynthetic carbon reduction (PCR) cycle? Explain the role of each stage. Draw a diagram of the stages by utilizing drawing tools in Microsoft® Word to aid your explanation.

When it comes to the process of photosynthetic carbon reduction cycle, also known as the Calvin cycle, there are three main steps to keep in mind: fixation, reduction, and regeneration. During the first step of fixation CO2 is taken into the plant through the use of ribulose bisphosphate (RuBP). During the next step of reduction NADPH and ATP are consumed and used to convert 3-phosphoglyceric acid to glyceraldehyde 3-phosphate. In the last step of the cycle, regeneration, the remainder of the ATP is consumed and the 3-phosphate is converted back to RuBP, starting the cycle all over again with a new CO2 molecule.

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1. Explain how the ATP and NADPH produced by the photosynthetic electron transport chain are used in the PCR cycle.

The ATP and NADPH produced by the photosynthetic electron transport chain are used in the Calvin cycle to reduce carbon dioxide to sugar. ATP acts as the energy source breaking off one of its phosphates groups and adding it to the phosphoglyceric acid and then the NADPH comes in to reduce the new compound by adding electrons to it and essentially helping to form sugar. The cycle uses the ATP and NADPH to convert three molecules of carbon dioxide to one molecule of a 3-carbon sugar.

1. What roles do light and Rubisco play in regulating the PCR cycle? Explain your answer.

The most important enzyme in the Calvin cycle is the one that starts the cycle off, that enzyme is ribulose-1-5-biphosphate carboxylase, also known as Rubisco. Rubsicso catalyzes the transformation of the sugar and carbon dioxide to the phosphoglycerates. If Rubisco does not give the go ahead the whole process comes to a stop, therefore it is a major factor in the PCR cycle. Light is responsible for the formation of the energy needed for the cycle to occur, therefore without it the cycle comes to a halt as well.