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Lectures 18-20 Chloroplasts and Photosynthesis

Lectures 18-20 Chloroplasts and Photosynthesis -...

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Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Chloroplasts and photosynthesis: the other half of the energy cycle  
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Chloroplasts are found in higher plants, algae, and two types of bacteria Mesophyll cell Mesophyll Vein Stomata CO 2 O 2 Chloroplast 5 µm 1 µm Outer membrane Intermembrane space Inner membrane Thylakoid Thylakoid Space Granum Storma Leaf cross section
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Chloroplast anatomy is similar to that of mitochondria suggesting that we see some familiar biochemistry
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CO 2 CALVIN CYCLE O 2 [CH 2 O] (sugar) NADP + ADP + P i An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle H 2 O Light LIGHT REACTIONS Chloroplast ATP NADPH
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Overview of the light dependent reactions 1. Pigment molecules capture energy from light 2. Energy conversions produce NADPH and ATP (used in the Calvin cycle to produce sugar)
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The electromagnetic spectrum: to understand photosynthesis we need to know some basic properties of light. Light travels in discrete packets called “photons”; the different colors of light travels in photons with different wavelengths ***longer wavelength = lower energy*** Gamma rays X-rays UV Infrared Micro- waves Radio waves 10 –5 nm 10 –3 nm 1 nm 10 3 nm 10 6 nm 1 m 10 6 nm 10 3 m 380 450 500 550 600 650 700 750 nm Visible light Shorter wavelength Higher energy Longer wavelength Lower energy
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Why leaves are green: interaction of light with chloroplasts Light Reflected Light Chloroplast Absorbed light Granum Transmitted light Chloroplasts reflect and transmit green light and absorb many of the other colors. The photons are absorbed by pigment molecules in the thylakoid membrane.
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The primary pigment is chlorophyll, an amphipathic molecule. There are other pigments that are orange, yellow, and red. These are the basis of the color change of leaves in the fall. C CH CH 2 C C C C C C N N C H 3 C C C C C C C C C N C C C C N Mg H H 3 C H C CH 2 CH 3 H CH 3 C H H CH 2 CH 2 CH 2 H CH 3 C O O O O O CH 3 CH 3 CHO in chlorophyll a in chlorophyll b Porphyrin ring: Light-absorbing
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