Ch. 10 notes

Ch. 10 notes - Ch. 10 17:03 Photosynthesis conversion of...

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Ch. 10 17:03 Photosynthesis – conversion of light energy into chemical energy that is stored in sugar and other organic molecules; carried out by chloroplast in plants Autotrophs – “self-feeders,” sustain themselves without eating anything derived from other living beings, produce organic molecules from CO 2 and other inorganic raw materials from environment = producers (ultimate sources of organic compounds for all non-autotrophic organisms Plants = photoautotrophs – organisms that use light as a source of energy to synthesize organic substances Heterotrophs – obtain their organic material from other organisms = consumers Light energy chemical energy for food Chloroplasts – found mainly in the cells of the mesophyll, the tissue in the interior of the leaf CO 2 enters leaf, and O 2 exits through stomata (microscopic pores) H 2 O absorbed by the roots leaves (through veins, which also export sugar to roots) One mesophyll cell has about 30-40 chloroplasts 2 membranes surround a dense fluid called stroma, in which are suspended thylakoids (inside is thylakoid space) thylakoid sacs are stacked in columns called grana chlorophyll – resides in thylakoid membrane of chloroplasts, absorb light energy 6CO 2 + 12 H 2 O + light energy C 6 H 12 O 6 + 6 O 2 + 6 H 2 O First hypothesis of photosynthesis – predicted that the O 2 released during photosynthesis came from O 2 Co 2 C + O 2 C + H 2 O [CH 2 O] Was challenged by C.B. van Niel, who studied bacteria, which did not release O 2 CO 2 + 2 H 2 S CH 2 O + H 2 O + 2S New hypothesis: plants split H 2 O as a source of electrons from H atoms, releasing O 2 as a by- product Redox reactions becomes reduced
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2 + 12 H 2 O C 6 H 12 O 6 + 6 O 2 becomes oxidized water is split and electrons are transferred along with H + ions from the water to carbon dioxide, reducing it to sugar electrons increase in potential energy as they move from water to sugar, so this process requires energy (endergonic. ..the energy comes from light) 2 stages of photosynthesis light reactions – “photo” Calvin cycle – “synthesis” Light reactions – steps of photosynthesis that converts solar energy to chemical energy, occurs in thylakoids of the chloroplast Water is split source of electrons and H + ions O 2 = waste product Light absorbed by chlorophyll drives a transfer of the electrons and H + ions from water to an acceptor called NADP + (nicotinamide adenine dinucleotide phosphate), where they are temporarily stored Use solar power to reduce NADP + to NADPH by adding a pair of electrons and H + Generate ATP using chemiosmosis to power the addition of a phosphate group to ADP (photophosphorylation) Light energy chemical energy in the form of 2 compounds NADPH ATP Calvin cycle – Melvin Calvin = dark/light-independent reactions
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This note was uploaded on 03/14/2012 for the course BISC 220 taught by Professor Mcclure during the Spring '09 term at USC.

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Ch. 10 notes - Ch. 10 17:03 Photosynthesis conversion of...

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