Light-dependent Reactions Flashcards
What happens in the LD reactions?
Light is absorbed and solar energy is converted into chemical energy
What are the products of LD reactions in terms of light-independent reactions?
The reactants for LI.
What are the reactants of LD reactions?
NADP+ (H+ and e- acceptor), H2O (is split to release H+, e-, and O2), and light (energized e- to continue process).
What are the products of LD reactions?
NADPH+H+ and ATP. (O2 exits)
What are the major steps of LD reactions?
Absorption of light and photolysis of H2O.
What is light energy used for?
To produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen.
What is photophosphorylation?
The process of generating ATP from ADP and phosphate by means of a proton-motive force generated across the thylakoid membrane of the chloroplast.
What is chemiosmosis?
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP.
When is an electron excited?
When the electron is at a higher energy level due to the chlorophyll absorbing light.
When is a chlorophyll photoactivated?
When the electron is excited.
How do single chlorophyll molecules re-emit energy?
The excited electron drops back down to its original level, which re-emits energy.
Where is chlorophyll located within the cell?
In the thylakoid membrane, within photosystems.
What is the first step in linear electron flow?
The photon energy excites pigment moleculesi n PSII, bouncing energy until it reaches e- in P680 (chlorophyll a)
What are P680 and P700?
These are reaction center chlorophyll. They best accept 680nm and 700nm.
Where are P680 and P700 found?
P680: PSII. P700: PSI
What is the second step in linear electron flow?
Electrons from P680 move to primary e- acceptor.
What is the third step in linear electron flow?
H2O is split filling P680 with e-, which releases O2 and H+ proteins.
What is step number four in linear electron flow and why is it so important?
e- moves from PSII through e- transport chain. This powers cytochrome C, moving H+ from stroma to thylakoid space (photophosphorylation in terms of chemiosmosis).
Describe step five in linear electron flow. This step is also very important because…
ATP synthase is activated by the gradient (chemiosmosis) to make ATP (photophosphorylation).
What is step six in linear electron flow?
e- moves to PSI to re-energize via ferredoxin. This repeats.
What is step seven in linear electron flow?
e- reduces NADP+ to NADPH+H+ (for the Calvin Cycle)
Which way do hydrogen ions flow in photosynthesis to form the gradient?
From the thylakoid space to the stroma.
In cellular respiration, which way do hydrogen ions flow to form the gradient?
From the intermembrane space to the matrix.
Is energy released at more place than one?
Yes, but only at th ATP synthase is there enough energy released to form a molecule or ATP.
