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Energy Metabolism: Photosynthesis (Energy and Reducing Power (2…
Energy Metabolism: Photosynthesis
Energy and Reducing Power
2 theoretical ways to transport energy from energized pigments into endergonic reactions
pigments enter reaction; difficult to control b/c not mobile
pigment make smaller, less energetic intermediates; mobile/ easily controlled
ATP is converted to ADP and phosphate by metabolic reactions
When electron are added to an atom, it becomes reduced
a reducing reaction reduces the positive charge on an atom, and an oxidative reaction increases the positive charge
oxidized compound often (but not always) contain a great deal of oxygen, which has a strong tendency to pull electrons away from an atom and raise that atom's partial positive
reduced compounds contain hydrogen, which becomes more stable by giving electrons reducing partner's positive charge
Oxidizing agents - oxidize the material they react with Ex: NAD+ and NADH+, because they take electrons away from other molecules
Reducing agents - place electrons onto other molecules, reducing those molecules and becoming oxidized themselves Ex: NADH and NADPH
Redox potential is the tendency to accept or donate electrons
Photosynthesis
a process that converts light energy to chemical energy
produces complex organic compounds
6CO2 + 6H20 + (energy) → C6H12O6 + 6O2 Carbon dioxide + water + energy from light produces glucose and oxygen.
External and Environmental Factors
Light
Quality, quantity and duration of light directly impact plant growth
Plants and Light video
quality of light refers to the colors or wavelengths it contains
quantity of light refers to the light intensity or brightness, which is affected by many factors
duration of light refers to the amount of time that a plant is exposed to sunlight
light compensation point is the light intensity on the light curve where the rate of photosynthesis exactly matches the rate of cellular respiration
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Leaf structure - absorb CO2, but inefficient for conserving water
small internal surface area = water loss is reduced, making it difficult to dissolve CO2 from air into cytoplasm
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minimize water loss while maintaining photosynthesis = reduce external surface by cylindrical leaves
water movement from interior air spaces to exterior air is minimized b/c so few stomata are present
photosynthesis is reduced b/c absorption of CO2 is slowed
Water - amount of water greatly affects photosynthesis
C4 metabolism and Crassulacean acid metabolism (CAM)
metabolic adaptations that conserve water
C4 and CAM cycles link
C4 - initial carbon fixation takes place in mesophyll cells and the Calvin cycle takes place in bundle-sheath cells. PEP carboxylase attaches an incoming carbon dioxide molecul to the three-carbon molecule PEP, producing oxaloacetate (a four-carbon molecule)
work cited
CAM - at night, CAM plants separate their stomata allowing CO2 to diffuse into leaves; during the day, CAM plants do not open their stomata but they still photosynthesis
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CAM pathway
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C4 pathway
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CAM pathway # C4 pathway #