Living Environment – Lesson 41
Danta/Meeker
Name_______________________
Photosynthesis I – Light Reactions
Do Now: What do chloroplasts do? Where are they found? (Lesson 40)
Explore: Read the article and answer the questions
There was a point on Earth where there was no oxygen in the atmosphere. Obviously this
period of time came way before humans first walked the earth. Around 2.3 billion years ago an
event called the Great Oxygenation Event (GOE) occurred leading to major changes in the
atmosphere as well as the types of organisms on earth. In this event Cyanobacteria began making
oxygen through photosynthesis at rates so high that it could no longer be tied up to Iron, which is
how it was before this event. Oxygen is toxic to many anaerobic organisms, leading many to go
extinct. This caused on of the biggest extinction events in the history of earth. GOE was not all
bad, as it led to over 2500 new minerals being found on earth as well as creating the oxygen
which would drive evolution of many new species including animals and later humans.
What was the Great Oxygenation Event?
What caused the GOE?
How long ago did the GOE happen?___________________
Why did the GOE lead to a mass extinction?
*Challenge* Do you think that there was lots of respiration prior to the GOE? Explain
Photosynthesis: Process converting _______________ into chemical _________________
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Energy is stored in _______________________
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Performed by most ______________, __________________, and __________________
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Performed differently by ________________________
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Evolved __________________
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Living Environment – Lesson 41
Danta/Meeker
Thylakoid: Compartment found inside the __________________________
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Site of ___________________________________ of photosynthesis
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Typically form ___________________ called grana
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Most important part is its _________________________
Light Reactions: Light energy is converted to chemical energy in form of __________________
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Also called ________________________________ and _________________________
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Requires ____________________
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Occurs on _____________________________
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Consists of _____________________________________
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Final electron acceptor _______________________________
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First electron donor is ________________________
o Creates ____________________
Electron transport chain: Series of compounds that transfer _________________
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Located _____________________________________
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Contains two __________________________
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Water donates electron and gets converted to ______________________
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Light hits ____________________________
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___________________ and __________________ are made
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ATP is made by ____________________________
Do you think this ETC is the same as in respiration? Explain
What type of reactions happen when electrons are gained? ___________________________
Photosystems: Two proteins in ETC that ________________________ and transfer __________
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Photosystem _____ is first part of ___________________________
o Splits _____________________
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Light gets absorbed by _____________________ at center
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Living Environment – Lesson 41
Danta/Meeker
Products of the light reaction
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______________________, ___________________ and _________________
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Products go to power _______________________________
Why is it so important for plants to hold on to water?
What would happen if photosynthesis stopped after the light reactions?
What would human life be like if we had chloroplasts on our skin?
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