· Light energy is converted to chemical energy in the form of ATP.
· Consist of cyclic photophosphorylation involving only photosystem I and
non-cyclic photophosphorylation involving both photosystems II and I.
· Light energy captured by pigments/light harvesting complexes passed to
special chlorophyll a, causing excitation of electrons to
higher energy level, which is subsequently captured by primary electron acceptor.
· For cyclic photophosphorylation, excited electrons are returned back to
special chlorophyll a (final electron acceptor), after passing down chain of electron carriers and proton pumps.
· For non-cyclic photophosphorylation, Photosystem I receives replacement of
electrons from photosystem II,
· photosystem II receives replacement of electrons from photolysis of water with
production of oxygen as byproduct.
· Excited electrons are passed along a chain of electron carriers of progressively
lower energy level/electron transport chain, energy released used by proton pumps to
pump H+ from stroma into thylakoid space.
· Creating a proton gradient across thylakoid membrane.
· ATP synthase harness proton gradient/proton motive force to generate ATP as
H+ diffuse back into stroma via ATP synthase.
· Chemiosmosis couples energy released from passage of electrons down
electron transport chain to active transport of H+ from stroma into thylakoid space
via proton pumps.
· For non-cyclic photophosphorylation, NADP reductase combines electrons with H+
and NADP+ (final electron acceptor) to form NADPH for use in Calvin cycle.
Miss Teong,
ReplyDeleteYour third point:
· Light energy captured by pigments/light harvesting complexes passed to
special chlorophyll a (final electron acceptor), causing excitation of electrons to
higher energy level, which is subsequently captured by primary electron acceptor.
The final electron acceptor is for cyclic photo-phosphorylation is it? Because if its non-cyclic its NADP. I think its not clear is it? Just checking.
Thanks!
Hi,
DeleteI think there is a typo (refer to latest edited post). Thanks for pointing it out.
But yes, final electron acceptor for cyclic photophosphorylation is special chl a molecules while for noncyclic photophosphorylation is NADP.
Hello Miss Teong,
ReplyDeleteAccording to page 17 of photosynthesis notes, it is mentioned that chemiosmosis is the process where EN is release from passage of electrons down ETC, used for active transport of protons (H+) from stroma into thylakoid space.
I want to ask if Chemiosmosis is actually the 7th point in the essay which is:
· Excited electrons are passed along a chain of electron carriers of progressively
lower energy level/electron transport chain, energy released used by proton pumps to
pump H+ from stroma into thylakoid space.
In addition the 2nd last point states that:
· Chemiosmosis couples energy released from passage of electrons down electron transport chain to active transport of H+ from stroma into thylakoid space
via proton pumps.
Does it mean the same thing?
Also does the proton pump refer to the cytochrome complex?
Thanks!
Yes, they mean the same thing (extra marking points).
DeleteThe 7th point is the description of the Chemiosmosis process while the 2nd last point is the mentioning of the process name. You can actually merge these points together.
And yes, the proton pump refers to the cytochrome complex.
Hello Miss Teong,
ReplyDeleteIs there a difference between electron transport system (ETS) and electron transport chain (ETC) or are they the same?
Thanks!
Yes they mean the same thing. But we usually use ETC as it suggests that there is a particular sequence of electron carriers.
DeleteHi,
ReplyDeleteOn page 15 of photosynthesis notes point 5 eqn is:
2H+ +2e- + NADP+ ---> reduced NADP (NADPH) + H+
the H+ at the end was asked to be insert into the eqn in the notes.
However, why can't we have the eqn just as:
H+ + 2e- + NADP+ ---> reduced NADP (NADPH)
THANKS!
Hi, this is to balance the charges. I think you may want to double check with your chem teacher for this one.
DeleteIf I am not wrong, one e- is used to neutralise the (+) charge on NADP+, and then one e- combines with one H+ to form a H atom, which is accepted by NADP to form NADPH.
This article is very good .check for lysosomes
ReplyDelete