Oxidized (blue) DPIP becomes colorless when it is reduced that is, when it receives electrons....


Oxidized (blue) DPIP becomes colorless when it is reduced that is, when it receives electrons. A diagram of the photosynthetic light reaction shows that water molecules are the source of these electrons. How is it that the DPIP was only able to receive reducing electrons from the photosystems (and ultimately from the water) when the lights were on, but not when the lights were off? Since the cuvette is mostly full of water, it is not the case that water is the limiting factor. Explain: what is the role of light energy in this system, and why does it make a difference in the reduction of the dye?

Discrete Energy States

Our current understanding of quantum mechanics states that energy levels are discrete, rather than continuous. That is to say, energy only exists at certain values in a spectrum, and energy cannot rest between these specific values. This is important to consider in the movement of electrons, as they can only exist at these known, discrete energy levels and not in between.

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The start of the Electron Transport Chain (ETC) is Photosystem II (PSII); this is where the electron donated from water starts. Without light, the...

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The Electron Transport Chain: Products and Steps


Chapter 8 / Lesson 5

What is an electron transport chain (ETC)? Learn where the ETC takes place. See electron transport chain steps along with its reactants and products.

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