BIO 101 1st EditionLecture 15Outline of Last LectureI. Fermentationa. Products of glycolysisII. RespirationIII. Photosynthesisa. Calvin cycleb. Light reactionsOutline of Current LectureI. Calvin CycleII. Light Reactionsa. Photosystem Ib. Photosystem IIIII. The Circle of LifeChapter 10 cont.Calvin Cycle- Called a cycle because one of the beginning reactant (RuBP) is regenerated- Anabolic pathway (requires ATP)] both come from- Reduction (requires source of electrons)] light reactionsLight Reactions- Conversion of light energy to make ATP and a reduced coenzyme (NADPH)- Occurs on thylakoid membranes of chloroplast- Uses 2 photosystems= light harvesting units on the thylakoid membraneso Group of 200-300 pigment molecules arranged like an ANTENNA to capture light energy - Photosystem I (PSI) and Photosystem II (PSII)- Three kinds of pigments: chlorophyll A + B, carotenoids- PSI and PSII have slightly different populations of pigments and capture light energy of slightly different wavelengthsBIO 101 1st Edition- The two photosystems are connected by an electron transport chain- Coenzyme oxidized from NADP+ is converted to NADPH (reduced form)- available to donate electrons to Calvin Cycle- The electrons are “knocked off” PSII by light and transferred along electron transport chain via PSI, eventually to NADP+ NADPH- PSII electrons are replaced by H2O=H2O splitting reaction: electrons go to PSII, H+ go into thylakoid space, O2 is released as gas- H+ are also transferred into the thylakoid space as electrons are passed alongelectron transport chain that connects PSII to PSI- H+ gradient results from H2O splitting reaction and from electron transport chain= PROTON MOTIVE FORCE- ATP is produced by chemiosmosis (using energy of a proton gradient to makeATP)- The photosynthetic ATP synthase is on the thylakoid membrane and produces ATP in the stromaThe Circle of Life - Connection between respiration and photosynthesis- Products of one are the beginning reactants of the otherBIO 101 1st Edition- Without photosynthesis- all living things would die; run out of food and
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