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36 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Photosynthesis
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- Light energy stored as chemical energy
- Original source of energy for other organisms |
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general equation for photosynthesis
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6CO2 + 12H2A -> C6H12O6 + 6H2O + 12A
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photosynthesis could be divided into two general parts
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1. Photochemical reactions (light reactions)
2. Temperature-sensitive reactions (previously called dark reactions) |
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Photochemical reactions
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-Light reactions
-Insensitive to temperature changes |
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Temperature-sensitive reactions
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-Previously called dark reactions
-Enzymatic reactions -Do not depend directly on light -Chloroplast proteins regulate activities of some dark reactions |
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Chloroplast Structure
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-Double-membrane envelope
-Two types of internal membranes -Grana (singular, granum) -Stroma lamella – interconnect grana |
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Stroma
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Solution made up of grana and stroma lamella
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Broken plastids
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Carry out only part of photosynthetic reactions
Will liberate oxygen |
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Intact chloroplasts
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carry out complete process of photosynthesis
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Green thylakoids (grana)
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-Capture light
-Liberate O2 from H2O -Form ATP from ADP and phosphate -Reduce NADP+ to NADPH |
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Colorless stroma
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-Contain water-soluble enzymes
-Captures CO2 -Uses energy from ATP and NADPH in sugar synthesis |
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% of light used for photosynthesis
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0.3% to 0.5%
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Factors Affecting Productivity/Photosynthesis : Temperature
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-Most plants function best between temperatures of 10C and 25C
-Above 25C Continuous decrease in photosynthesis rate as temperature increases |
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Factors Affecting Productivity/Photosynthesis: Light
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-Light intensity and wavelength affect photosynthesis rate
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Factors Affecting Productivity/Photosynthesis: Carbon dioxide
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Artificial increase in carbon dioxide may increase rate of photosynthesis for limited period
Level injurious to some plants after 10 to 15 days of exposure |
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Factors Affecting Productivity/Photosynthesis: Water
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Rate of photosynthesis may be changed by small differences in water content of chlorophyll-bearing cells
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Factors Affecting Productivity/Photosynthesis: Mineral Nutrients
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Poor soils can result in plants with poorly developed photosynthetic capacities
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Factors Affecting Productivity/Photosynthesis
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-Light
-Water -Mineral Nutrients -Temperature -Carbon Dioxide |
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Structural adaptations that diminish light intensity that reaches chloroplasts
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Surface hairs, thick cuticle, thick epidermis
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Net photosynthetic rate?
Gross photosynthetic rate? |
Gross - total amount of sugar produced
Net - amount of sugar after cost of photosynthesis |
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Light
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Packet of energy (photons) make up light
Blue light has more energy per photon than does red light |
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Instrument used to measure amount of specific wavelength of light absorbed by a pigment
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Spectrophotometer
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Chlorophyll
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-Reflects green light
-Absorbs blue and red wavelengths -Chlorophylls a and b |
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Absorption of Light Energy by Chlorophyll
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-Absorbed energy transferred to adjacent pigment molecule (resonance)
-Energy eventually transferred to chlorophyll a reception center 1. Series of steps drives electrons from water to reduce NADP+ 2. Formation of NADPH represents conversion of light energy to chemical energy 3. NADPH reduces CO2 in enzymatic reactions leading to sugar formation |
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Photosystem I
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-Chlorophyll a and b
-P700 -Greater proportion of chlorophyll a than b in *light-harvesting complex, sensitive to longer wavelength light |
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Photosystem II
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-Chlorophyll a and b, carotene
-P680 |
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Photophosporylation
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Light-driven production of ATP in chloroplasts
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Cyclic photophosphorylation
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No O2 liberated
No NADP+ is reduced ATP production Only photosystem I involved |
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Noncyclic photophosphorylation
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-Photosystems I and II are involved
-ATP and NADPH are formed Energy drives CO2 reduction reactions of photosynthesis |
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Ribulose biphosphate carboxylase/oxygenase (rubisco)
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Catalyzes first step in carbon cycle of photosynthesis
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C3 Pathway
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-CO2 enters cycle and combines with RuBP produced in *stroma
-Energy stored in NADPH and ATP (light reactions) transferred into stored energy in phosphoglyceraldehyde (PGAL) -PGAL may be enzymatically converted to 3-C sugar -Two molecules of 3-C sugar phosphate combine to form fructose 1,6 -transformed into starch -RuBP is regenerated |
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C4 Pathway
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Ensures an efficient absorption of CO2 and results in low CO2 compensation point
-CO2 produced by respiration/CO2 absorbed during photosynthesis |
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C3 Plants
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-High rates of photorespiration
-Produce less sugar during hot, bright days of summer, under milder conditions are more efficient because they expend less energy to capture CO2 |
-Stomata are open during the day
-Photosynthesis takes place throughout the leaf -more efficient than C4 and CAM plants under cool and moist conditions and under normal light -Most plants are C3 |
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C4 Plants
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-Show little or no photorespiration
-Produce 2 or 3 times more sugar than C3 plants during hot, bright days of summer |
-Stomata are open during the day
-Photosynthesis takes place in inner cells -Photosynthesizes faster than C3 plants under high light intensity and high temperatures, better Water Use Efficiency -Corn, many grasses |
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Photorespiration
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Under high light and high heat, the enzyme (RUBISCO) that grabs carbon dioxide for photosynthesis may grab oxygen instead, causing repiration to occur instead of photosynthesis, thus reducing the production of sugars from photosynthesis.
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CAM
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Stomata open at night, Leaves rapidly absorb CO2
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-Stomata open at night
-The CO2 is converted to an acid and stored during the night -succulents such as cactuses and agaves and also some orchids |
