Photosynthesis Year 2 PT.2 Flashcards
What does non-cyclic phosphorylation produce
ATP, Reduced NADP and O2
Where are photosystems in the thylakoid membrane linked by
Electron carriers
What are electron carriers
Proteins that transfer electrons
What do the photosystems and electron carriers form_____
An electron transport chain
What are electron transport chains
A chain of proteins through which excited electrons flow
What are the steps to light energy exciting electrons in chlorophyll
Light energy is absorbed by PSII
The light energy excites electrons in chlorophyll
The electrons move to a higher energy level
These high energy electrons are released from the chlorophyll and move down the electron transport chain to PSI
What does photolysis of water produce
Protons (H+) ions, electrons and O2
What are all the steps to photolysis of protons, electrons and O2
As the excited electrons from chlorophyll leave PSII to move down the electron transport chain, they must be replaced
Light energy splits water into protons (H+ protons) electrons and Oxygen - photolysis
The reaction is H2O—–>2H^+ +. 1/2 O2
What does energy from the excited electrons make
ATP
How do energy from the excited electrons make ATP
The excited electrons lose energy as they move down the electron transport chain
This energy is used to transport protons into the thylakoid, so that the thylakoid has a higher concentration of protons than the stroma. This forms a proton gradient across the thylakoid membrane.
Protons move down their concentration gradient, into the stroma, viap the enzyme ATP synthase, which is embedded in the thylakoid. The energy from this movement combines ADP and inorganic phosphate to form ATP
What else does energy from the excited electrons generate
Reduced NADP
How does energy from the excited electrons generate reduced NADP
Light energy is absorbed by PSI which excites the electrons again to an even higher energy level
Finally the electrons are transferred to NADP, along a proton from the stroma, to form reduced NADP
What is chemi osmosis
The process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthesis and chemiosmosis is described by the chemiosmosis theory
What does cyclic phosphorylation only produce and only use
It only produces ATP and only uses PSI
Why is it called CYCLIC phosphorylation
Because the electrons from the chlorophyll molecule aren’t passed onto NADP but are passed back to PSI via electron carriers
This means the electrons are recycled and can repeatedly flow through PSI. This process doesn’t produce any reduced NADP or O2. It only produces small amounts of ATP
