ETIABO: Photosynthesis - Light Dependent reaction Flashcards
The light-dependent reaction in such detail as to show that: chlorophyll absorbs light, leading to photoionisation of chlorophyll some of the energy from electrons released during photoionisation is conserved in the production of ATP and reduced NADP the production of ATP involves electron transfer associated with the transfer of electrons down the electron transfer chain and passage of protons across chloroplast membranes and is catalysed by ATP synthase embedded in these membranes (chemiosomot
What are the two stages of photosynthesis?
- Light dependent reaction
- Light independent reaction
Where does the LDR specifically occur?
Thylakoid membranes
Photosynthesis occurs in a plants ______, more specifically the thylakoid membranes within the chloroplasts.
Leaves
The thylakoid membranes sit inbetween the ______ and the _____.
- Stroma
- Thylakoid space
What coenzyme catalyses the reaction between ADP + Pi?
ATP synthase
ATP synthase is an enzyme that catalyses the reaction between ____ + ___ to make ____.
ADP + Pi
ATP
ATP synthase requires energy to combine ADP and Pi to produce ATP. This energy comes from ____ ions
Hydrogen
The catalysing of ADP + Pi requires energy. Where is this energy sourced from?
The movement of protons via chemiosmosis (photophosphorylation)
Explain how H+ ions allow for ATP synthase to gain energy:
- There is a higher conc of H+ ions in the thylakoid space than in the stroma.
- H+ ions move from the thylakoid space into the stroma through ATP synthase (a semi-permeable membrane) down their proton gradient- from an area of higher proton conc to an area of lower proton conc.
- This is known as chemiosmosis
A proton is another name for a _____.
Hydrogen ion (H+)
ATP synthase is NOT a _____ ______ but is instead an enzyme.
Transport protein
Briefly, what happens in photophosphorylation?
The movement of proton ions (chemiosmosis) through ATP synthase generates energy for the hydrolysis of ATP +Pi to make ATP.
The movement of protons during photophosphorylation is needed for ATP synthase to generate energy. How does the plant ensure that there is always a lower conc of protons in the stroma than in the thylakoid space?
- Active transport of protons from the stroma to the thylakoid space.
- Ensures there are less protons in the stroma than in the thylakoid space so the are able to diffuse when needed.
Gaining an electron is _______.
Reduction
Loosing an electron is _______.
Oxidation
When electrons gain energy, they are in an ______ state.
Excited
Briefly, what happens in photoionisation?
- Light hits the leaf, chlorophyll absorbs this light and light energy is transferred to electrons within the chlorophyll.
- Electrons enter an excited state and leave the chlorophyll.
- The chlorophyll becomes positively charged as it is oxidised.
Electrons move through the electron transport chain via a series of ______-______ reactions which release energy to allow the active transport of protons from the stroma to the thylakoid space.
Oxidation-reduction
To maintain a proton gradient between the stroma and thylakoid space, protons are actively transported from the stroma to the thylankoid space using ATP. Where does this ATP come from?
After photoionisation (where excited electrons are released from the chlorophyll to the ETC), electrons move along the ETC via oxidation-reduction reactions, which provides energy to the protein complex responsible for the active transport of protons.
NADP is a coenzyme. What is meant by that?
A molecule that helps enzymes carry out its function.
What happens once electrons have reached the end of the ETC and cannot go any further?
- NADP reacts with the electrons and a proton (from the stroma)
- Forms NAHDPH (reduced NADP- as it is gaining electrons)
What are the two products of the LDR?
ATP
Reduced NADP (aka NADPH)
Name the stages of photosynthesis in order:
- Photophosphorylation
- Photoionisation
- ETC
- Photolysis
Briefly, what happens in photolysis?
Why does photolysis need to occur?
- Electrons are lost from the chlorophyll during photoionisation.
- These electrons need to be replaced in order for the LDR to repeat.
In photolysis what are electrons are replaced by?
- Protons
- Electrons
- Oxygen
What is the role of oxygen produced in replace of lost electrons in photoionisation?
- Used in respiration
OR - Diffuses out of the plant
During photolysis, once electrons in chlorophyll are lost during photoionsiation, they are replaced by ______.
Water
Where does photolysis take place?
Thylakoid space
Why is the thylakoid membrane having a large surface area an advantage?
Maximises the amount of ATP and NADPH that can be made at one time.
Proteins in the grana hold the chlorophyll in such a way so that _________________.
Maximum amount of light can be absorbed
Why are thylakoid membranes semi-permeable?
Allows a proton gradient to be established.
Chloroplasts contain both DNA and ribosomes. Why is this an advantage for photosynthesis?
The proteins involved in the light-dependent reaction can be easily and quickly produced.
