Bios 208 1st Edition Lecture 23 Outline of Last Lecture I. The Versatility of CatabolismII. Biosynthesis (Anabolic Pathways)III. Photosynthesis Feeds the BiosphereIV. Tracking Atoms through PhotosynthesisV. The Splitting of WaterVI. Photosynthesis as a Redox ProcessVII. The Two Stages of PhotosynthesisOutline of Current Lecture I. The Nature of SunlightII. Photosynthetic Pigments: The Light ReceptorsCurrent LectureI. The Nature of SunlightA. Light is a form of electromagnetic energy, also called electromagnetic radiation.B. Like other electromagnetic energy, light travels in rhythmic waves.C. Wavelength is the distance between crests of waves.D. Wavelength determines the type of electromagnetic energy.E. The electromagnetic spectrum is the entire range of electromagnetic energy, or radiation.F. Visible light consists of wavelengths (including those that drive photosynthesis) that produce colors we can see.G. Light also behaves as though it consists of discrete particles, called photons.II. Photosynthetic Pigments: The Light ReceptorsA. Pigments are substances that absorb visible light.B. Different pigments absorb different wavelengths.C. Wavelengths that are not absorbed are reflected or transmitted.D. Leaves appear green because chlorophyll reflects and transmits green light.E. A spectrophotometer measures a pigment’s ability to absorb various wavelengths.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.F. This machine sends light through pigments and measures the fraction of light transmitted at each wavelength.G. An absorption spectrum is a graph plotting a pigment’s light absorption versus wavelength.H. The absorption spectrum of chlorophyll a suggests that violet-blue and red light work best for photosynthesis.I. An action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process.J. The action spectrum of photosynthesis was first demonstrated in 1883 by Theodor W. Engelmann.K. In his experiment, he exposed different segments of a filamentous alga to different wavelengths.L. Areas receiving wavelengths favorable to photosynthesis produced excess O2.M. He used the growth of aerobic bacteria clustered along the alga as a measure of O2 production.N. Chlorophyll a is the main photosynthetic pigment.O. Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis.P. Accessory pigments called carotenoids absorb excessive light that would damage
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