Photosynthesis =Transformation of solar energy into chemical energy of carbohydrates Carried out by plants, algae, and cyanobacteria
Photosynthesis Begins with the products of cellular respiration C 2 and H 2 Carbons join together and hydrogens (taken from water) are added to the carbons Solar energy is required, ENDTHERMIC End product is CH 2 Glucose = C 6 H 12 6. xygen is a byproduct. Solar Energy Basic Reaction H 2 + C 2 (CH 2 ) + 2 Balanced Reaction 6H 2 + 6C 2 C 6 H 12 6 + 6 2
Carbon from C 2 build the sugar backbone C Photosynthesis C C C Hydrogens from water populate the Carbons H H H H C C H H H H ccurs in the Chloroplast xygen from water forms 2
C Photosynthesis H C H C C H H C C H H H H H
Site of Photosynthesis: Tour of the leaf.
Photosynthesis Summary
Electron micrograph of Chloroplast Close up of grana
Sunlight adsorption spectrum
Photosynthesis Summary
Photosystem solar panels for gathering solar energy and passing it to the reaction center (a chlorophyll molecule).
Collecting Solar Energy: 2 photosystems carrie r carrier electrons H2 II Energy will generate ATP I 2H+ + 1/22 Calvin Cycle Chlorophyll is left without an electron, it therefore grabs an electron from water, splitting water into H + ions and 2.
The photosystems reside in the grana membranes
The Entire Light Reaction Series
Electron carriers transport electrons; H+ ions are attracted Electron Carrier carrier carrier carrier e - e - H + is attracted to the electrons e - e - H 2 carrier The carriers do not bind e - or H +, they carry them (like your hand carrying a cup)
The Dark Reactions Calvin Cycle Powered by ATP generated by the light reactions End product is glucose C 6 H 12 6 3 steps 1. Carbon dioxide fixation 2. Addition of H + and electrons 3. Regeneration of first substrate (RuBP)
The Calvin Cycle C 2 A carbon ( ) enters the cycle It hooks onto a 5-carbon chain The 5-carbon molecule is remade ATP ATP The resulting 6- carbon molecule is split into 2 molecules A 3-carbon chain leaves the cycle glycerol 3-phosphate or G3P
Balancing the reactions The 5 3-carbon molecules are rearranged into 3 5-carbon molecules (requires energy!!) ATP ne 3-carbon chain leaves the cycle glycerol 3- phosphate or G3P 3 C 2 3 carbons ( ) enter the cycle These 3 carbons hook onto a total of 3 5- carbon chains ATP The resulting 6- carbon molecules are split into 6 3 carbon molecules (requires energy!!) Adding Carbons to the chain requires H+ and electrons the Carrier molecule delivers H+ and electrons
And by now, you are all wondering.. What is the fate of the G3P?
Plants and algae can make any molecule they need from G3P. They can form... The fate of G3P amino acids, fatty acid and glycerol glucose for energy needs sucrose for transport through plant starch for storage cellulose for cell walls
Photosynthesis Summary G3P Glucose
Why do we find different types of plants in different areas? Palm trees in florida Maples here Part of the answer is different TYPES of photosynthesis
Photorespiration and Plant Adaptation Glitch in the system: Rubisco often combines 2 instead of C 2 with RuBP, unproductively. ccurs with one 2 for every three C 2. This wastes energy, and compromises food production in crops that use C 3 cycle. Especially problematic in hot weather because of water evaporation. Plant closes stomata in leaves to prevent evaporation, but as water is kept in, C 2 is kept out. As the light-dependent reactions continue, 2 builds up, combining with RuBP unproductively.
Photorespiration and Plant Adaptation C 4 plants. warm climate. Grasses, corn. They shuttle incoming C 2 to bundle-sheath cells. Costs ATP in sunny climates this is not an issue, because with abundant sunlight, ATP is plentiful. In northern climates, C 4 plants are not as well adapted.
CAM Plants crassulacean acid metabolism Adaptation that saves water in hot climates. Cactus, pineapple, mint, and orchid. Close stomata during the day; open them at night. Start C 4 metabolism at night by fixing C 2 but wait for day to use abundant ATP to finish.
Night Mesophyll C C 2 2 cell C 2 uptake storage Calvin Cycle Calvin Cycle transport (w Calvin Cycle sugar Mesophyll cell sugar Bundle Sheath cell Day sugar Mesophyll cell C3 C4 CAM Most plants Corn, grass Cactus, pineapple warm environments dry environments