Photosynthesis - Cyanobacteria 7groupsofalgae Chloroplast

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Photosynthesis Overview -Energy for all life on Earth ultimately comes from photosynthesis -Oxygenic photosynthesis is carried out by: - Cyanobacteria - 7 groups of algae - All land plants - chloroplasts Chloroplast -Thylakoid membrane - internal membrane - Contains chlorophyll and other photosynthetic pigments - Pigments clustered into photosystems -Grana —> stacks of flattened sacs of thylakoid membrane -Stroma lamella —> connect grana -Stroma —> semiliquid surrounding thylakoid membranes Stages -Light-dependent reactions —> require light - Capture energy from sunlight - Make ATP and reduce NADP+ to NADPH -Carbon fixation reactions or light-independent reactions —> does NOT require light - Use ATP and NADPH to synthesize organic molecules from CO2 Pigments  —> molecules that absorb light energy in the visible range -Light is a form of energy -Photon —> particle of light - Acts as a discrete bundle of energy - Energy content of a photon is inversely proportional to the wavelength of the  light -Photoelectric effect —> removal of an electron from a molecule by light Absorption Spectrum  —> range & efficiency of photons molecule is capable of  absorbing -When a photon strikes a molecule, its energy is either: - Lost as heat - Absorbed by the electrons of the molecule - Boosts electrons into higher energy level Pigments in Photosynthesis -Organisms have evolved a variety of different pigments -Only two general types are used in green plant photosynthesis - Chlorophylls - Carotenoids -In some organisms, other molecules also absorb light energy
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Chlorophyll -Chlorophyll a —> main pigment in plants and cyanobacteria -Only pigment that can act directly to convert light energy to chemical energy -Absorbs violet-blue and red light -Chlorophyll b —> accessory pigment or secondary pigment absorbing light  wavelengths that chlorophyll a does not absorb -Structure of chlorophyll - Porphyrin ring —> complex ring structure with alternating double and single  bonds - Magnesium ion at the center of the ring - Photons excite electrons in the ring - Electrons are shuttled away from the ring -Action Spectrum - Relative effectiveness of different wavelengths of light in promoting  photosynthesis - Corresponds to the absorption spectrum for chlorophylls Carotenoids
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