Chapter 10.2.2 (Exam 2) Photosysnthesis Flashcards
Photosynthesis Converts Light Energy into Chemical Energy
What are the two photosystems used by noncyclic electron transport?
Photosystem II
Photosystem I
What chlorophyll is present in Photosystem II?
Photosystem II has P680 chlorophyll —absorbs best at 680 nm
What chlorophyll is present in Photosystem I?
Photosystem I has P700 chlorophyll —absorbs best at 700 nm
How does Photosystem II contribute to the electron transport chain?
When excited chlorophyll (Chl*) gives up its electron, it is unstable, and grabs another electron from water
The water becomes oxidized
H+ from H2O and electron transport capture energy for the chemiosmotic synthesis of ATP
What is the chemiosmotic synthesis of ATP?
The H+ ion gradient is used by ATP synthase to manufacture ATP molecules
What is the primary function of Photosystem II?
Splitting water molecules (oxidizing water) to release oxygen and create a proton gradient for ATP synthesis
What is the primary function of Photosystem I?
Reducing NADP+ to NADPH, which is used in the Calvin cycle (the next step in photosynthesis) to build sugars
How does Photosystem I reduce NADP+ to NADPH?
An excited electron from the Chl* reduces an acceptor
The oxidized Chl+ takes an electron from the last carrier in PS II
The energetic electron is passed through several carriers until it reaches NADP+ reductase, an enzyme that reduces NADP+ to NADPH
What will happen if you stop the transfer of electrons from the electron carriers to NADP+ reductase?
NADPH wouldn’t be formed
Lack of NADPH will limit the Calvin cycle
What is cyclic electron transport?
Uses photosystem I and electron transport to produce ATP instead of NADPH
Why is it called cyclic electron transport?
The electron from the excited chlorophyll passes back to the same chlorophyll
Where in the chloroplast is H+ transported into to create an electrochemical gradient?
Across the thylakoid membrane from the stroma into the lumen of the thylakoid
How is ATP formed in the ETC in chlorophyll?
ATP is formed by photophosphorylation, a chemiosmotic mechanism
What are the two mechanisms that help create the H+ gradient in addition to the electron transport chain?
NADP+ reduction - removes H+ in the stroma
H2O oxidation - creates more H+ in the lumen
What is the function of the high H+ concentration across the thylakoid membrane?
High H+ concentration in the lumen drives H+ back into the stroma through ATP synthase channels to form ATP
