2-29 photosynthesis - PHOTOSYNTHESIS LIFE 8.0 8.3 8.1 What...

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PHOTOSYNTHESIS LIFE 8.0 – 8.3 8.1 What is photosynthesis? - Photosynthesis (literally, “synthesis from light”) is a metabolic process by which the energy of sunlight is captured and used to convert carbon dioxide and water into carbohydrate sugars and oxygen gas: 6 CO 2 + 6 H 2 O → C 6 H 12 O 6 + 6 O 2 -all the oxygen gas produced during photosynthesis comes from water 8.1.1 Photosynthesis involves two pathways -The reactions of photosynthesis are commonly divided into two main pathways: light reactions : driven by light energy ; converts light energy into chemical energy in the form of ATP and a reduced electron carrier (NADPH + H + ). l ight-independent reactions : do not use light directly, but instead use ATP, NADPH + H + (made by the light reactions ), and CO 2 to produce sugars. There are three different forms of the light- independent pathway that reduces CO 2 : the Calvin cycle , C 4 photosynthesis , and crassulacean acid metabolism . 8.2.1 Light behaves both a particle and a wave -Light is a form of electromagnetic radiation . It comes in discrete packets called photons . Light also behaves as if it were propagated in waves. The amount of energy contained in a single photon is inversely proportional to its wavelength : the shorter the wavelength , the greater the energy of the photons 8.2.2 Absorbing a photon excites a pigment molecule -When a photon meets a molecule , one of three things happens: The photon may bounce off the molecule—it may be scattered or reflected . The photon may pass through the molecule—it may be transmitted . The photon may be absorbed by the molecule . -in the case of absorption, the photon disappears, but the energy is does not. When a molecule absorbs a photon , that molecule acquires the energy of the photon . It is thereby raised from a ground state (with lower energy ) to an excited state (with higher energy ) more chemically reactive 8.2.3 Absorbed wavelengths correlate with biological activity - Molecules that absorb wavelengths in the visible spectrum —that region of the spectrum that is visible to
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2-29 photosynthesis - PHOTOSYNTHESIS LIFE 8.0 8.3 8.1 What...

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