Www.soran.edu.iq M. Saadatian Photosynthesis 1. Photosynthesis.
1 Review Summarize what happens during the light dependant reactions 2 Explain How do each of the...
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Transcript of 1 Review Summarize what happens during the light dependant reactions 2 Explain How do each of the...
1 Review Summarize what happens during the light dependant reactions
2 Explain How do each of the three primary factors affect the rate of photosynthesis
3 Review What are the different ways that plants cope with water shortages
Light Dependant Reactions: Generating ATP and NADPH
Photosystems Series of proteins in the thylakoid that absorb sunlight
and make high-energy electrons.
Electron Transport Chain
Series of electron carriers that shuttle high-energy electrons during ATP-generating reactions
Electron Transport Chain (ETC).
Photosystem II Thylakoid provides new
electrons from water Water breaks up into 2
electrons, 2 H+ ions, and 1 oxygen atom.
Photosystem II 2 electrons replace the
high-energy electrons that have been lost to ETC
H+ ions released inside thylakoid
Oxygen is released into the air.
Photosystem II Energy from electrons
is used by proteins in ETC to pump H+ ions from the stroma into the thylakoid space.
Photosystem I
Electrons used energy to pump H+ ions so have less energy
Photosystem I uses energy from light to reenergize the electrons.
Photosystem I
After 2nd ETC, NADP+ molecules in the stroma pick up high-energy electrons and H+ ions at the outer surface of the thylakoid membrane to become NADPH.
Hydrogen Ion Movement and ATP Formation
H+ ions accumulate within the thylakoid space from splitting water and pumping them across.
Hydrogen Ion Movement and ATP Formation
H+ ions cannot directly cross membane ATP synthase
Protein that allows H+ ions to pass through Causes it to rotate and bind ADP and a phosphate.
The Light-Independent Reactions: Producing Sugars
Called the Calvin Cycle Plants use ATP and NADPH to build stable high-
energy carbohydrate compounds that can be stored for a long time.
Carbon Dioxide Enters the Cycle
Carbon dioxide molecules enter the Calvin cycle from the atmosphere
Combine CO2 with 5-carbon compounds 6 CO2 enter, twelve 3-carbon compounds are
produced.
Sugar Production Remaining ten 3-
carbon molecules are converted back into six 5-carbon molecules
Combine with the new CO2 to start the next cycle.
ATP
ADP
Summary of the Calvin Cycle Uses 6 molecules of
carbon dioxide to produce a single 6-carbon sugar.
ATP
ADP
Energy for the reactions is supplied by compounds produced in the light-dependent reactions.
ATP
ADP
Sugars are used by the plant for energy needs and to build other macromolecules for growth and development.
ATP
ADP
Temperature
Enzymes work best between 0°C and 35°C Lower temps slow enzymes Higher temps denature enzymes.
Light Intensity
High light intensity increases the rate of photosynthesis
There is a maximum to light intensity increasing photosynthesis.
Water Availability
Water is needed in the reaction Water shortage can stop reaction Certain plants have special adaptations
C4 plants CAM plants.
C4 Photosynthesis
Very good and getting CO2 Uses a 4 carbon molecule Requires added energy Corn, sugar cane, and sorghum.
CAM Plants
Open their leaves at night and trap CO2
Seal leaves shut during day to conserve water and use trapped CO2
Pineapple trees and many desert cacti.