Chapter 10 Notes

Chapter 10 Notes - Chapter 10 Notes 10.1 Photosynthesis...

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Chapter 10 Notes 10.1 Photosynthesis converts light energy to the chemical energy of food 1. Overview a. The process of photosynthesis originated in a group of bacteria that had infolded regions of the plasma membrane containing clusters of such photosynthetic enzymes and molecules, similar to a chloroplast. In fact, the original chloroplast is believed to have been a photosynthetic prokaryote that lived inside a eukaryotic cell. 2. Chloroplasts a. Leaves are major part of photosynthesis. b. Chloroplasts are mainly found in the mesophyll of cells, the tissue in the interior of the leaf. c. Stomata are microscopic pores (CO 2 enters and O 2 exits) d. A mesophyll cell has about 30 to 40 chloroplasts, each organelle measuring 2-4 um by 4-7 um. e. A two-membrane envelope encloses the stroma , the dense fluid within the chloroplast. f. An elaborate system of interconnected membranous sacs called thylakoids segregrates the stroma from the thylakoid space, the interior of the thylakoid. g. Chlorophyll resides in the thylakoid membranes. 3. Tracking Atoms Through Photosynthesis: Scientific Inquiry a. Equation: 6CO 2 +12H 2 O + Light Energy---- C 6 H 12 O 6 + 6O 2 + 6H 2 O b. The chloroplasts splits water into hydrogen and oxygen. c. C.B. van Niel of Stanford concluded that carbon dioxide is not split into carbon and water. Oxygen doesn’t come from CO 2 but H 2 O. d. Both photosynthesis and cellular respiration involved redox reactions. Photosynthesis reverses the direction of electron flow. Water is split, and electrons are transferred along with hydrogen ions from the water to carbon dioxide, reducing it to sugar. This process requires energy. 4. The Two Stages of Photosynthesis a. Light reactions is the photo part of photosynthesis and the Calvin cycle is the synthesis part. b. The light reactions convert solar energy to chemical energy. Water is split, providing a source of electrons and protons, giving off O 2 as a by-product. c. Light absorbed by chlorophyll drives a transfer of the electrons and H+ ions from water to an acceptor called NADP+ , where they are temporarily stored. d. NAD+ and NADP+ differ in the presence of an extra phosphate group in the NADP+ molecule. e. The light reactions also generate ATP, using chemiosmosis to power the addition of a phosphate group to ADP, called photophosphorylation . Thus, light energy is converted to NADPH (source of electrons as “reducing power” that can be passed along to an electron acceptor) and ATP. f. The Calvin Cycle us named after Melvin Calvin. It begins by incorporating CO 2 from the air into organic molecules already present in the chloroplast ( carbon fixation) . It then reduces the fixed carbon to carbohydrate by the addition of electrons. The reducing power is provided by NADPH, which acquired its cargo of electrons from the light reactions. To convert CO 2 to carbs, it also uses ATP. 10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH
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This note was uploaded on 02/07/2012 for the course BIO 1711 taught by Professor Burleson during the Spring '11 term at North Texas.

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Chapter 10 Notes - Chapter 10 Notes 10.1 Photosynthesis...

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