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Ch. 10 - Photosynthesis

Chapter 10, Problem 1

How is energy transferred among antenna pigment molecules? a. by heat b. by redox reactions c. by fluorescence d. by resonance

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Hi everyone. Let's look at our next question. It says which one of the following statements is true. So let's look through our statements here. Choice A says energy is transferred among an antenna pigment molecules by heat. Well, this is not true antenna pigment molecules may give off heat, but that's a way to give off excess energy. In the case of a plant being in high light conditions, if it's absorbing too much light energies, it can radiate some energy off as be given off as heat. But that's not how it transfers energy among the pigment molecules. Choice B says energy is transferred among antenna pigment molecules by residents. Well, this is a true statement. This is our correct answer. When light hits the pigment molecules, uh one of their electrons gets excited and this energy is passed on from electron, the electron in the antenna with each electron getting excited until it gets to the reaction center. At that point that electron will get handed off to an electronic sector and go down the electron transport chain. But among the antenna pigment molecules themselves, its resonance that excitement energy being passed on through the series of conjugated double bonds in those pigment molecules. So that's a true statement. And just to be thorough, let's look on at our other choices. Choice C says energy is transferred among antenna pigment molecules by redox reactions. Well, that's not correct. Redox reactions occur later on in the electron transport chain. That's part of the reaction center that occurs after antenna pigment molecules absorb energy from the sunlight. So antenna pigment molecules pass along that energy through resonance. Then afterwards that electron is given to an electronic sector in the reaction center, and then the electron transport chain transfers energy by redox reactions, but not the antenna pigment molecules. So C. Is not our answer. Finally, Choice D energy is transferred among antenna pigment molecules by fluorescence. And that is also not our correct answer, fluorescence is what happens when you have excess energy being given off. You see that for instance, if you extract pigments from the plants, so their structures are destroyed, they contain the electron transport chain. Um light energy absorbed by the pigments can be given off as fluorescence and or heat. So that's a way of giving off energy from those pigments, but not from transferring energy amongst themselves. So, Choice D. Is not a correct answer. So, again, the answer here, Choice B. Energy is transferred among antenna pigment molecules by residents. See in the next video