BIOS E-1a Lecture 07 092811 annotated

BIOS E-1a Lecture 07 092811 annotated - Lecture 7...

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Unformatted text preview: Lecture 7: Photosynthesis Reading: Chapter 6 (concepts 6.5-6.6) Spalding et al. paper 1 Photosynthesis • Energy within light is captured and used to synthesize carbohydrates 6CO 2 + 6H 2 O + light energy → C 6 H 12 O 6 + 6O 2 • CO 2 is reduced • H 2 O is oxidized • Energy from light drives this endergonic reaction Photosynthesis • Energy within light is captured and used to synthesize carbohydrates 6CO 2 + 6H 2 O + light energy → C 6 H 12 O 6 + 6O 2 • CO 2 is reduced • H 2 O is oxidized • Energy from light drives this endergonic reaction 2 Photosynthesis powers the biosphere • Biosphere: regions on the surface of the Earth and in the atmosphere where living organisms exist • Largely driven by the photosynthetic power of green plants • Cycle where cells use organic molecules for energy and plants replenish those molecules using photosynthesis – Plants also produce oxygen 3 Trophic levels • Heterotroph – Must eat food, organic molecules from their environment, to sustain life • Autotroph – Make organic molecules from inorganic sources • Photoautotroph – Use light as a source of energy – Green plants, algae, cyanobacteria 4 Photosynthesis and cellular respiration are linked 5 Chloroplast • Organelles in plants and algae that carry out photosynthesis • Chlorophyll: green pigment • Majority of photosynthesis occurs in leaves in mesophyll • Stomata: carbon dioxide enters and oxygen exits leaf 6 Chloroplast anatomy • Outer and inner membrane – Intermembrane space • 3 rd membrane - thylakoid membrane contains pigment molecules – Forms thylakoids – Enclose thylakoid lumen • Granum: stack of thylakoids • Stroma: fluid filled region between thylakoid membrane and inner membrane 7 Leaf structure and composition 8 2 stages of photosynthesis • Light reactions – Uses light energy – Take place in thylakoid membranes – Produce ATP, NADPH and O 2 • Calvin cycle – Occurs in stroma – Uses ATP and NADPH to incorporate CO 2 into organic molecules 9 Two stages of photosynthesis 10 Light energy • Type of electromagnetic radiation • Travels as waves – Short to long wavelengths • Also behaves as particles - photons – Shorter wavelengths have more energy 11 Electromagnetic spectrum 12 • Photosynthetic pigments absorb some light energy and reflect others – Leaves are green because they reflect green wavelengths • Absorption boosts electrons to higher energy levels • Wavelength of light that a pigment absorbs depends on the amount of energy needed to boost an electron to a higher orbital Plants use light in the visible portion of the spectrum 13...
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This note was uploaded on 02/09/2012 for the course BIOLOGY 102 taught by Professor Anderson during the Spring '11 term at Harvard.

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BIOS E-1a Lecture 07 092811 annotated - Lecture 7...

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